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Sample records for chloranil

  1. Electrical transport in ethyl cellulose–chloranil system

    Indian Academy of Sciences (India)

    P K Khare; R K Pandey; P L Jain

    2000-08-01

    The charge-transport behaviour in pure and chloranil (Chl) doped ethyl cellulose (EC) system has been studied by measuring the dependence of current on field, temperature, electrode material and dopant concentration. The role of doping molecular concentration in the polymer matrix and modification in the conduction characteristics are studied. Lowering of the activation energy due to doping was observed. The current was found to increase with an increase in the chloranil concentration. An explanation for this has been attempted on the basis of formation of molecular aggregates between chloranil molecules and ethoxy groups of ethyl cellulose. It is suggested that chloranil occupies interstitial positions between the polymer chains and assists in carrier transportation by reducing the hopping barriers. The current–voltage characteristics of different samples are analyzed using space charge limited current theory and quantitative information about the transport parameters is derived. The values of effective drift mobility and trapped charge carrier concentration which result in the build up of space charge have been calculated.

  2. Investigation of ground state charge transfer complex between paracetamol and p-chloranil through DFT and UV-visible studies

    Science.gov (United States)

    Shukla, Madhulata; Srivastava, Nitin; Saha, Satyen

    2012-08-01

    The present report deals with the theoretical investigation on ground state structure and charge transfer (CT) transitions in paracetamol (PA)/p-chloranil (CA) complex using Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TD-DFT) method. It is found that Cdbnd O bond length of p-chloranil increases on complexation with paracetamol along with considerable amount of charge transfer from PA to CA. TD-DFT calculations have been performed to analyse the observed UV-visible spectrum of PA-CA charge transferred complex. Interestingly, in addition to expected CT transition, a weak symmetry relieved π-π* transition in the chloranil is also observed.

  3. Redetermination of pyridine-4-carbonitrile–chloranilic acid (1/1 at 180 K

    Directory of Open Access Journals (Sweden)

    Hiroyuki Ishida

    2008-07-01

    Full Text Available In the crystal structure of the title compound, C6H4N2·C6H2Cl2O4, two chloranilic acid (systematic name: 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone molecules are connected by O—H...O hydrogen bonds to form a dimeric unit. The pyridine-4-carbonitrile molecules are linked on both sides of the dimer via N...H...O hydrogen bonds to give a centrosymmetric 2:2 complex of pyridine-4-carbonitrile and chloranilic acid. The H atom in the N...H...O hydrogen bond is disordered over two positions with approximately equal occupancies. The pyridine ring makes a dihedral angle of 61.54 (14° with the chloranilic acid plane. The 2:2 units are further linked by intermolecular C—H...O and C—H...Cl hydrogen bonds. This determination presents a siginficantly higher precision crystal structure than the previously published structure [Tomura & Yamasshita (2008. X-ray Struct. Anal. Online, 24, x31–x32].

  4. Quantitation of sodium 35S-sulphate in nano mole levels by spectrophotometric assay using barium chloranilate and liquid scintillation counting

    International Nuclear Information System (INIS)

    In this assay, the absorbance of chloranilic acid released from buffered suspension of barium chloranilate, taken in excess, on reaction with solutions of known concentrations of authentic sodium sulphate (2-10 fg; 14-70 nanomoles) and that of sodium 35S-sulphate of known radioactivity (10-20 mci; 370-740 mBq) is measured spectrophotometrically and the quantitation done accordingly. The amount of chloranilic acid released has been found to be directly proportional to the amount of sulphate present in the original sample solution. (author). 8 refs., 1 tab

  5. Inelastic neutron scattering study of tetramethylpyrazine in the complex with chloranilic acid

    International Nuclear Information System (INIS)

    The tunnel splitting of the methyl librational ground states in the hydrogen bonded tetramethylpyrazine-chloranilic acid (TMP-CLA) complex are determined for temperatures T≤28 K by high resolution neutron spectroscopy. Three tunnel modes are resolved at T = 2.4 K. Their relative intensities show that the crystal structure must be different from the proposed space group. Tunnelling and methyl librational modes from the measured density of states are combined into rotational potentials. There are discrepancies of activation energies calculated for these potentials and those obtained from quasielastic scattering of neutrons at T≥50 K due to structural differences in the two respective temperature regimes. Rotational potentials in TMP-CLA are significantly weaker as in pure TMP

  6. Structural evidence of ferrielectric neutral-ionic layered ordering in 2,6-dimethyltetrathiafulvalene-p-chloranil

    International Nuclear Information System (INIS)

    Direct structural evidence of the periodic ordering of neutral and ionic planes is reported for 2,6-dimethyltetrathiafulvalene-p-chloranil, detected by high-resolution x-ray diffraction experiments. Simultaneous to the neutral-ionic layered ordering, theoretically predicted a long time ago to occur in stages, an antiparallel dimerization ordering takes place, leading to a 'ferrielectric' structure. Both intramolecular deformations and intermolecular contacts, related to the charge-transfer ordering and to the dimerization process, are discussed and compared with results obtained for the prototype compound of the neutral to ionic transition, tetrathiafulvalene-p-chloranil. Thus essential insights are provided for an understanding of the mechanism of this unusual electronic-structural instability, and important physical features are discussed such as the interstack interactions, the coupled order parameters, and the interplay between the staging and condensation mechanisms

  7. Analytic techniques to quantify Tetrachlorohydroquinone and Chloranil; Tecnicas analiticas para cuantificar Tetraclorohidroquinona y Cloranilo

    Energy Technology Data Exchange (ETDEWEB)

    Castillo Escobedo, Ma. Teresa; Gutierrez de Gonzalez, Luz Ma; Gojon Zorrilla, Gabriel [Universidad Autonoma de Nuevo Leon, Monterrey, Nuevo Leon (Mexico)

    1995-02-01

    Tetrachlorohydroquinone (TCHQ) was determined by two methods: iodometry and cerimetry. Tritation with aqueous ceric ammonium sulphate using potentiometric end-point detection proved to be the method of choice on account of its coefficient of variation (CV=0.475%) and its excellent accuracy. Chloranil (TCQ) was quantified by titration with aqueous ascorbic acid in acetone-water-hexamethylene tetramine (HMT), the golden-yellow color of the TCQ-HMT complex disappearing at the end point. This method is accurate and has CV=0.396%. [Spanish] Se cuantifico la tetraclorohidroquinona (TCHQ) mediante una tecnica yodometrica y un metodo potenciometrico, basado en el uso de sulfato cerico amoniacal. Se concluyo que el metodo potenciometrico es el mejor, ya que tiene un coeficiente de variacion (CV) de 0.475%, y una exactitud muy aceptable. Se desarrollo un tecnica para cuantificar el Cloranilo (TCQ) por titulacion con Acido Ascorbico en presencia de Hexametilentetramina (HMT) en medio acetona-agua; el punto final se determino por la separacion del color amarillo oro del complejo TCQ-HMT. Esta tecnica presenta un coeficiente de variacion (CV) de 0.396% y una exactitud aceptable. Se realizaron pruebas de hipotesis para verificar la exactitud de los metodos elegidos.

  8. Study and Elimination of the Interference of Aluminium on the Voltammetric Determination of Uranium with Chloranilic Acid. Application to the Determination of Uranium in Waters and Geological Samples

    International Nuclear Information System (INIS)

    The interference of aluminium during the voltammetric determination of uranium with 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid) has been investigated. The presence of aluminium originates a voltammetric signal due to its chloranilic acid complex at the same potential range as the uranium analytical signal appears. The interference of aluminium can be overcome by addition of an appropriate amount of sodium fluoride as complexing reagent. The determination of uranium by adsorptive stripping voltammetry (AdSV) can be carried out at concentration levels as low as 1 μg/L in the presence of 100 μg/L aluminium after the addition of 100μL of 0.1 mol/L NaF. The method can be applied to the determination of uranium in aluminium-containing waters and geological samples containing high aluminium levels. (Author) 19 refs

  9. Solvent-drop Assisted Mechanochemical Synthesis of the Black and Green Polymorphs of the Tetrathiafulvalene-chloranil Charge Transfer Salt

    Energy Technology Data Exchange (ETDEWEB)

    S Benjamin; S Pagola; Z Huba; E Carpenter; T Abdel-Fattah

    2011-12-31

    This work describes the synthesis of the green and black polymorphic forms of the tetrathiafulvalene-chloranil (TTF-CA) charge transfer salt as pure phases, by solvent-assisted mechanochemistry. Both materials were characterized using laboratory and high-resolution X-ray powder diffraction (XRPD), elemental analysis and scanning electron microscopy (SEM). The high-resolution XRPD pattern of the TTF-CA black polymorph was indexed with a triclinic lattice a = 10.756(5) {angstrom}, b = 11.057(4) {angstrom}, c = 6.614(2) {angstrom}, {alpha} = 101.36(2){sup o}, {beta} = 93.69(3){sup o}, {gamma} = 89.37(3){sup o}, V = 769.6(5) {angstrom}{sup 3}. The chemical stability of these phases upon heating was investigated using thermogravimetric analysis (TGA), elemental analysis and X-ray powder diffraction (XRPD), indicating that both polymorphs undergo chemical decomposition, and ruling out the transition to an air-stable high temperature polymorph.

  10. Thermal degradation kinetics and solid state, temperature dependent, electrical conductivity of charge–transfer complex of phenothiazine with chloranil and picric acid

    Indian Academy of Sciences (India)

    M A Ashok; B N Achar

    2008-02-01

    Temperature dependent electrical conductivity and thermal degradation kinetics of charge–transfer (C–T) complexes of phenothiazine (PTZ) with -chloranil (CHL) and picric acid (PA), are reported. These C–T complexes exhibited semiconducting behaviour. The activation energies for PTZ–CHL and PTZ–PA complexes are calculated based on their electrical conductivities measured over the temperature ranges 30–110°C and 30–90°C, respectively. And these energies for PTZ–CHL and PTZ–PA are 0.54 eV and 0.75 eV, respectively. The complexes are analysed for the kinetic parameters like the activation energy for decomposition and the Arrhenius pre-exponential factors in their pyrolysis region using Broido’s, Coats–Redfern as well as Horowitz–Metzger methods. Using standard equations, thermodynamic parameters such as enthalpy, entropy and free energies, are calculated.

  11. Spectroscopic characterization of charge transfer complexes of 2,3-diaminopyridine with chloranilic acid and dihydroxy-p-benzoquinone in polar solvent

    Science.gov (United States)

    Al-Ahmary, Khairia M.

    2014-01-01

    Charge transfer (CT) complexes formed between 2,3-aminopyridine (2,3-DAP) as electron donor with the π-electron acceptors chloranilic acid (CHA) and dihydroxy-p-benzoquinone (DHBQ) were investigated spectrophotometrically in ethanol. Minimum-maximum absorbance method has been used for estimating the formation constants of the charge transfer reactions (KCT). Job's method of continuous variation and photometric titration studies were used to detect the stoichiometric ratios of the formed complexes and they showed that 1:1 complexes were produced. The molar extinction coefficient (ε), oscillator strength (f), dipole moment (μ), charge transfer energy (ECT), ionization potential (IP) and the dissociation energy (W) of the formed complexes were estimated, they reached acceptable values suggesting the stability of the formed CT-complexes. The solid CT-complexes were synthesized and characterized by elemental analyses, 1H NMR and FTIR spectroscopies where the formed complexes included proton and electron transfer.

  12. DFT calculations of 2,6-dimethylpyrazine (26DMP) and its complex with chloranilic acid (CLA): Comparison to INS, IR and Raman vibration spectra

    Science.gov (United States)

    Pawlukojć, A.; Sobczyk, L.; Prager, M.; Bator, G.; Grech, E.; Nowicka-Scheibe, J.

    2008-12-01

    The inelastic neutron scattering (INS), infrared and Raman spectra of crystalline 2,6-dimethylpyrazine (26DMP) and its complex with chloranilic acid (26DMP·CLA) were measured. Simultaneously the DFT calculations of the molecular structures and frequencies of the normal vibrations were performed by using various functionals. The INS spectra were simulated in the energy range up to 1200 cm -1, on the basis of the calculated frequencies. A very good conformity was obtained between experimental and calculated data with respect to the structure as well as to frequencies, with exception, however, of the CH 3 torsional modes. The structural analysis based on the deviation from the sum of the van der Waals radii showed that the packing of the methyl groups in the 26DMP·CLA complex was markedly stronger than that in the neat 26DMP. However, the DFT calculations overestimated the role of this effect that may be due to a limitation of the applied methods. In addition the anharmonicity of the rotational potential led to the librational energies different from those obtained using a harmonic potential.

  13. Electric response in the antiferroelectric crystal of 4,4′-di-t-butyl-2,2′-bipyridyl with chloranilic acid

    International Nuclear Information System (INIS)

    Highlights: • The semiconducting properties of the crystals were disclosed in the organic complex. • Dielectric relaxation and dc conductivity were investigated. • Activation energy for the thermally activated processes of the σdc was estimated. • The effect of hydrogen bonds on the mechanism of the phase transition and the electric properties of the crystal was discussed. - Abstract: The electric response was analyzed in the vicinity of the structural phase transition at 412 K in the single crystals of 2,5-dichloro-3,6-dihydroxy-p-benzoquinone (chloranilic acid, CLA) with 4,4′-di-t-butyl-2,2′-bipyridyl (dtBBP). The dielectric permittivity of the complex measured along the b direction between 300 and 440 K and at frequencies ranging from 500 Hz to 2 MHz indicates two phenomena. At low frequencies, dielectric losses are ascribed to the electric conductivity of the crystal, while at high frequencies, to the dielectric relaxation described by means of the Cole–Cole relationship. The parameters of the dielectric response: the relaxation time, τ, the dielectric increment, εο − ε∞, and the distribution parameter of the relaxation time, α, were estimated and analyzed. The low-temperature structure of the crystals indicates the antiferroelectric arrangement of the supramolecular hydrogen bonds. The dielectric results also presented for the deuterated crystals of dtBBP·CLA proved that the dynamics of protons in the hydrogen bonds are responsible for the mechanism of phase transition

  14. Electrochemical incineration of chloranilic acid using Ti/IrO{sub 2}, Pb/PbO{sub 2} and Si/BDD electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Huitle, C.A.; Ferro, S.; De Battisti, A. [Ferrara Univ. (Italy). Dept. of Chemistry; Quiroz, M.A. [Fundacion Universidad de las Americas-Puebla (Mexico). Departamento de Quimica y Biologia; Comninellis, C. [Swiss Federal Inst. of Technology, Lausanne (Switzerland). Inst. of Chemical Engineering

    2004-12-15

    The electrochemical oxidation of chloranilic acid (CAA) has been studied in acidic media at Pb/PbO{sub 2}, boron-doped diamond (Si/BDD) and Ti/IrO{sub 2} electrodes by bulk electrolysis experiments under galvanostatic control. The obtained results have clearly shown that the electrode material is an important parameter for the optimization of such processes, deciding of their mechanism and of the oxidation products. It has been observed that the oxidation of CAA generates several intermediates eventually leading to its complete mineralization. Different current efficiencies were obtained at Pb/PbO{sub 2} and BDD, depending on the applied current density in the range from 6.3 to 50 mA cm{sup -2}. Also the effect of the temperature on Pb/PbO{sub 2} and BDD electrodes was studied. UV spectrometric measurements were carried out at all anodic materials, with applied current density of 25 and 50 mA cm{sup -2}. These results showed a faster CAA elimination at the BDD electrode. Finally, a mechanism for the electrochemical oxidation of CAA has been proposed according to the results obtained with the HPLC technique. (Author)

  15. Spectroscopic investigation and computational analysis of charge transfer hydrogen bonded reaction between 3-aminoquinoline with chloranilic acid in 1:1 stoichiometric ratio

    Science.gov (United States)

    Al-Ahmary, Khairia M.; Alenezi, Maha S.; Habeeb, Moustafa M.

    2015-10-01

    Charge transfer hydrogen bonded reaction between the electron donor (proton acceptor) 3-aminoquinoline with the electron acceptor (proton donor) chloranilic acid (H2CA) has been investigated experimentally and theoretically. The experimental work included the application of UV-vis spectroscopy to identify the charge transfer band of the formed complex, its molecular composition as well as estimating its formation constants in different solvent included acetonitrile (AN), methanol (MeOH), ethanol (EtOH) and chloroform (CHL). It has been recorded the presence of new absorption bands in the range 500-550 nm attributing to the formed complex. The molecular composition of the HBCT complex was found to be 1:1 (donor:acceptor) in all studied solvents based on continuous variation and photometric titration methods. In addition, the calculated formation constants from Benesi-Hildebrand equation recorded high values, especially in chloroform referring to the formation of stable HBCT complex. Infrared spectroscopy has been applied for the solid complex where formation of charge and proton transfer was proven in it. Moreover, 1H and 13C NMR spectroscopies were used to characterize the formed complex where charge and proton transfers were reconfirmed. Computational analysis included the use of GAMESS computations as a package of ChemBio3D Ultr12 program were applied for energy minimization and estimation of the stabilization energy for the produced complex. Also, geometrical parameters (bond lengths and bond angles) of the formed HBCT complex were computed and analyzed. Furthermore, Mullikan atomic charges, molecular potential energy surface, HOMO and LUMO molecular orbitals as well as assignment of the electronic spectra of the formed complex were presented. A full agreement between experimental and computational analysis has been found especially in the existence of the charge and proton transfers and the assignment of HOMO and LUMO molecular orbitals in the formed complex as

  16. Electric response in the antiferroelectric crystal of 4,4′-di-t-butyl-2,2′-bipyridyl with chloranilic acid

    Energy Technology Data Exchange (ETDEWEB)

    Rok, M., E-mail: magdalena.rok@chem.uni.wroc.pl; Piecha-Bisiorek, A.; Szklarz, P.; Bator, G.; Sobczyk, L.

    2015-05-01

    Highlights: • The semiconducting properties of the crystals were disclosed in the organic complex. • Dielectric relaxation and dc conductivity were investigated. • Activation energy for the thermally activated processes of the σ{sub dc} was estimated. • The effect of hydrogen bonds on the mechanism of the phase transition and the electric properties of the crystal was discussed. - Abstract: The electric response was analyzed in the vicinity of the structural phase transition at 412 K in the single crystals of 2,5-dichloro-3,6-dihydroxy-p-benzoquinone (chloranilic acid, CLA) with 4,4′-di-t-butyl-2,2′-bipyridyl (dtBBP). The dielectric permittivity of the complex measured along the b direction between 300 and 440 K and at frequencies ranging from 500 Hz to 2 MHz indicates two phenomena. At low frequencies, dielectric losses are ascribed to the electric conductivity of the crystal, while at high frequencies, to the dielectric relaxation described by means of the Cole–Cole relationship. The parameters of the dielectric response: the relaxation time, τ, the dielectric increment, ε{sub ο} − ε{sub ∞}, and the distribution parameter of the relaxation time, α, were estimated and analyzed. The low-temperature structure of the crystals indicates the antiferroelectric arrangement of the supramolecular hydrogen bonds. The dielectric results also presented for the deuterated crystals of dtBBP·CLA proved that the dynamics of protons in the hydrogen bonds are responsible for the mechanism of phase transition.

  17. Spectrophotometric determination of repaglinide in tablets based on charge-transfer complexation reaction with chloranilic acid and dichloro-dicyano benzoquinone

    Directory of Open Access Journals (Sweden)

    Cijo Madathil X.

    2011-01-01

    Full Text Available Two simple, accurate, precise, inexpensive, selective and sensitive spectrophotometric methods are described for the determination of repaglinide (RPG in bulk drug and its tablets. The methods were based on the charge- transfer complex reaction between RPG in acetonitrile with p-chloranilic acid (CAA or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ in dioxane and subsequent formation of intensely colored radical anions of the reagents which were measured at 520 nm (CAA or 590 nm (DDQ. Several experimental variables affecting the complex formation, stability of the colored species and sensitivity of the reaction were optimized. Under the optimized conditions, Beer’s law was obeyed over the concentration ranges of 20-400 and 5-80 μg ml-1 RPG for CAA and DDQ methods, respectively, and the corresponding correlation coefficients were 0.9995 and 0.9998. The apparent molar absorptivity values were 1.02x103 and 4.60x103 for CAA and DDQ methods respectively, with corresponding Sandell sensitivity values of 0.4438 and 0.0984 μg cm-2. Limits of detection (LOD were calculated to be 7.07 and 2.42 μg ml-1 and the limits of quantification (LOQ were 21.43 and 7.33 μg ml-1 RPG, for CAA method and DDQ method, respectively. Validation results demonstrated that the inter day and intra day accuracy were up to 97.56%. The precision determined did not exceed 2.5% of RSD. The methods were successfully used for the determination of RPG in tablet form and the results were in good agreement with the label claims as shown by the recoveries which were in the range of 99.22- 102.8% with standard deviation values < 2%. The accuracy of the method was confirmed by recovery studies via standardaddition procedure with excellent recovery 98.24-104.0 ± 1.08-3.35.

  18. X-ray diffraction and inelastic neutron scattering study of 1:1 tetramethylpyrazine chloranilic acid complex: temperature, isotope, and pressure effects.

    Science.gov (United States)

    Prager, M; Pietraszko, A; Sobczyk, L; Pawlukojć, A; Grech, E; Seydel, T; Wischnewski, A; Zamponi, M

    2006-11-21

    The x-ray diffraction studies of the title complex were carried out at room temperature and 14 K for H/D (in hydrogen bridge) isotopomers. At 82 K a phase transition takes place leading to a doubling of unit cells and alternation of the hydrogen bond lengths linking tetramethylpyrazine (TMP) and chloranilic acid molecules. A marked H/D isotope effect on these lengths was found at room temperature. The elongation is much smaller at 14 K. The infrared isotopic ratio for O-H(D)...N bands equals to 1.33. The four tunnel splittings of methyl librational ground states of the protonated complex required by the structure are determined at a temperature T=4.2 K up to pressures P=4.7 kbars by high resolution neutron spectroscopy. The tunnel mode at 20.6 microeV at ambient pressure shifts smoothly to 12.2 microeV at P=3.4 kbars. This is attributed to an increase of the strength of the rotational potential proportional to r(-5.6). The three other tunnel peaks show no or weak shifts only. The increasing interaction with diminishing intermolecular distances is assumed to be compensated by a charge transfer between the constituents of deltae/e approximately 0.02 kbar(-1). The phase transition observed between 3.4 and 4.7 kbars leads to increased symmetry with only two more intense tunneling bands. In the isotopomer with deuterated hydrogen bonds and P=1 bar all tunnel intensities become equal in consistency with the low temperature crystal structure. The effect of charge transfer is confirmed by a weakening of rotational potentials for those methyl groups whose tunnel splittings were independent of pressure. Density functional theory calculations for the model TMP.(HF)2 complex and fully ionized molecule TMP+ point out that the intramolecular rotational potential of methyl groups is weaker in the charged species. They do not allow for the unequivocal conclusions about the role of the intermolecular charge transfer effect on the torsional frequencies. PMID:17129141

  19. Spectroscopic and structural characterization of the charge-transfer interaction of N,N'-bis-alkyl derivatives of 1,4,6,8-naphthalenediimide with chloranilic and picric acids

    Science.gov (United States)

    Refat, Moamen S.; Ahmed, Hamdy A.; Grabchev, Ivo; El-Zayat, Lamia A.

    2008-09-01

    Charge-transfer (CT) complexes formed from the reactions of two N,N'-bis-alkyl derivatives of 1,4,6,8-naphthalenediimide such as N, N'-bis[2-hydroxyethyl)]-1,4,6,8-naphthalenediimide (BHENDI) and N, N'-bis-[2- N, N-dimethylaminoethyl)]-1,4,6,8-naphthalenediimide (BDMAENDI) with chloranilic acid (CLA) and piciric acid (PA) as π-acceptors, have been studied spectrophotometrically in methanol and chloroform, respectively at 25 °C. The photometric titration curves for the reactions indicated that the data obtained refer to 1:1 charge-transfer complexes of [(BHENDI)(CLA)], [(BDMAENDI)(CLA)], [(BHENDI)(PA)] and [(BDMAENDI)(PA)] were formed. Benesi-Hildebrand and its modification methods were applied to the determination of association constant ( K), molar extinction coefficient ( ɛ). The solid CT complexes have been synthesized and characterization by different spectral methods.

  20. Hydrogen bonded NHO chains formed by chloranilic acid (CLA) with 4,4‧-di-t-butyl-2,2‧-bipyridyl (dtBBP) in the solid state

    Science.gov (United States)

    Bator, G.; Sawka-Dobrowolska, W.; Sobczyk, L.; Owczarek, M.; Pawlukojć, A.; Grech, E.; Nowicka-Scheibe, J.

    2012-01-01

    In crystalline state 2,5-dichloro-3,6-dihydroxy-p-benzoquinone (chloranilic acid, CLA) forms with 4,4'-di-t-butyl-2,2'-bipyridyl (dtBBP) the hydrogen bonded chains along the b-axis. From one side of the CLA molecule the proton transfer takes place and the hydrogen bond length is very short (2.615 Å). A continuous infrared absorption is observed for dtBBP·CLA in the wavenumber range between 3100 and 800 cm -1 also indicating the strong hydrogen bonds. The DSC measurements show a weak, close to continuous, phase transition at 414 K. The complex dielectric permittivity for a single crystal sample was measured in the temperature range 100-440 K and at frequencies between 200 Hz and 2 MHz. The dielectric response is a combination of semiconducting properties and a relaxation process most probably connected with the proton dynamics in the hydrogen bonds. The mechanism of the structural phase transition is discussed.

  1. Optical and positron annihilation spectroscopic studies on PMMA polymer doped by rhodamine B/chloranilic acid charge transfer complex: Special relevance to the effect of γ-ray irradiation

    Science.gov (United States)

    Hassan, H. E.; Refat, Moamen S.; Sharshar, T.

    2016-04-01

    Polymeric sheets of poly (methylmethaclyerate) (PMMA) containing charge transfer (CT) complex of rhodamine B/chloranilic acid (Rho B/CHA) were synthesized in methanol solvent at room temperature. The systematic analysis done on the Rho B and its CT complex in the form of powder or polymeric sheets confirmed their structure and thermal stability. The IR spectra interpreted the charge transfer mode of interaction between the CHA central positions and the terminal carboxylic group. The polymer sheets were irradiated with 70 kGy of γ radiation using 60Co source to study the enhanced changes in the structure and optical parameters. The microstructure changes of the PMMA sheets caused by γ-ray irradiation were analyzed using positron annihilation lifetime (PAL) and positron annihilation Doppler broadening (PADB) techniques. The positron life time components (τi) and their corresponding intensities (Ii) as well as PADB line-shape parameters (S and W) were found to be highly sensitive to the enhanced disorder occurred in the organic chains of the polymeric sheets due to γ-irradiation.

  2. Hydrogen bonded NHO chains formed by chloranilic acid (CLA) with 4,4′-di-t-butyl-2,2′-bipyridyl (dtBBP) in the solid state

    International Nuclear Information System (INIS)

    Graphical abstract: The molecular complex dtBBP·CLA, its crystal structure at 100 K, infrared, the DFT calculations, a phase transition at ca. 414 K, DSC, dielectric response analysis, proton dynamics, antiferroelectric properties. Highlights: ► We synthesized a novel molecular complex, dtBBP·CLA. ► We determined the crystal structure of dtBBP·CLA at 100 K. ► We detected a phase transition at 414 K in the complex and postulated its mechanism. ► We interpreted the infrared spectra of dtBBP·CLA. ► We used DFT to calculate the molecular structure of dtBBP·CLA in solid state. - Abstract: In crystalline state 2,5-dichloro-3,6-dihydroxy-p-benzoquinone (chloranilic acid, CLA) forms with 4,4′-di-t-butyl-2,2′-bipyridyl (dtBBP) the hydrogen bonded chains along the b-axis. From one side of the CLA molecule the proton transfer takes place and the hydrogen bond length is very short (2.615 Å). A continuous infrared absorption is observed for dtBBP·CLA in the wavenumber range between 3100 and 800 cm−1 also indicating the strong hydrogen bonds. The DSC measurements show a weak, close to continuous, phase transition at 414 K. The complex dielectric permittivity for a single crystal sample was measured in the temperature range 100–440 K and at frequencies between 200 Hz and 2 MHz. The dielectric response is a combination of semiconducting properties and a relaxation process most probably connected with the proton dynamics in the hydrogen bonds. The mechanism of the structural phase transition is discussed.

  3. Zirconoarylation of alkynes through p-chloranil-promoted reductive elimination of arylzirconates

    OpenAIRE

    Xiaoyu Yan; Chao Chen; Chanjuan Xi

    2014-01-01

    A novel method for the zirconoarylation of alkynes was developed. TCQ-promoted reductive elimination of arylzirconate [LiCp2ZrAr(RC≡CR)], which was prepared by the reaction of zirconocene–alkyne complexes with aryllithium compounds, afforded trisubstituted alkenylzirconocenes. This reaction can afford multi-substituted olefins with high stereoselectivity.

  4. Zirconoarylation of alkynes through p-chloranil-promoted reductive elimination of arylzirconates

    OpenAIRE

    Yan, Xiaoyu; Chen, Chao; Xi, Chanjuan

    2014-01-01

    A novel method for the zirconoarylation of alkynes was developed. TCQ-promoted reductive elimination of arylzirconate [LiCp2ZrAr(RC≡CR)], which was prepared by the reaction of zirconocene–alkyne complexes with aryllithium compounds, afforded trisubstituted alkenylzirconocenes. This reaction can afford multi-substituted olefins with high stereoselectivity.

  5. Mechanochemical Synthesis of Two Polymorphs of the Tetrathiafulvalene-Chloranil Charge Transfer Salt: An Experiment for Organic Chemistry

    Science.gov (United States)

    Wixtrom, Alex; Buhler, Jessica; Abdel-Fattah, Tarek

    2014-01-01

    Mechanochemical syntheses avoid or considerably reduce the use of reaction solvents, thus providing green chemistry synthetic alternatives that are both environmentally friendly and economically advantageous. The increased solid-state reactivity generated by mechanical energy imparted to the reactants by grinding or milling can offer alternative…

  6. X-ray diffraction and inelastic neutron scattering study of 2,6-dimethylpyrazine (DMP) chloranilic acid (CLA) complex

    Science.gov (United States)

    Prager, M.; Sawka-Dobrowolska, W.; Sobczyk, L.; Pawlukojć, A.; Grech, E.; Wischnewski, A.; Zamponi, M.

    2007-01-01

    The DMP · CLA and DMP · CLA-d 2 crystals below 100 K are monoclinic, space group P2 1/c with four molecules in the unit cells. Infinite chains of hydrogen bonded counterparts are formed with O⋯N distances equal to 2.767(2) and 2.639(2) for non-deuterated DMP · CLA. Deuteration leads to the Ubbelohlde effect particularly well manifested in the second short O-H⋯N bridge (elongation by ca. 0.02 Å). In the IR spectra a Hadži's trio of the broad absorption is observed characteristic of strong hydrogen bonds. In the INS spectra the vibrational density of states and methyl rotational tunnel splittings were determined. The temperature dependence of tunneling bands enabled to make mode assignments and to determine the methyl rotational potentials. Comparison of the results to the pure electron donor DMP was made and the difference found can be almost completely assigned to the steric changes of the environment. A weak isotope effect with deuteration of the OH⋯N bridges of the DMP · CLA complex is assigned to a charge transfer of δe/ e = 0.006.

  7. X-ray diffraction and inelastic neutron scattering study of 2,6-dimethylpyrazine (DMP) chloranilic acid (CLA) complex

    International Nuclear Information System (INIS)

    The DMP . CLA and DMP . CLA-d2 crystals below 100 K are monoclinic, space group P21/c with four molecules in the unit cells. Infinite chains of hydrogen bonded counterparts are formed with O...N distances equal to 2.767(2) and 2.639(2) for non-deuterated DMP . CLA. Deuteration leads to the Ubbelohlde effect particularly well manifested in the second short O-H...N bridge (elongation by ca. 0.02 A). In the IR spectra a Hadzi's trio of the broad absorption is observed characteristic of strong hydrogen bonds. In the INS spectra the vibrational density of states and methyl rotational tunnel splittings were determined. The temperature dependence of tunneling bands enabled to make mode assignments and to determine the methyl rotational potentials. Comparison of the results to the pure electron donor DMP was made and the difference found can be almost completely assigned to the steric changes of the environment. A weak isotope effect with deuteration of the OH...N bridges of the DMP. CLA complex is assigned to a charge transfer of δe/e = 0.006

  8. Nonmonotonous Interfacial Behavior of Chloranilic Acid and Its Voltammetrically Active Complexes with V and Mo on Mercury Electrode

    Czech Academy of Sciences Publication Activity Database

    Novotný, Ladislav; Navrátil, Tomáš; Sander, S.; Bašová, Pavlína

    2002-01-01

    Roč. 14, 15/16 (2002), s. 1105-1109. ISSN 1040-0397 R&D Projects: GA ČR GV204/97/K084; GA ČR GA203/98/P239 Institutional research plan: CEZ:AV0Z4040901 Keywords : vanadium complexes * voltammetry * mercury electrode Subject RIV: CG - Electrochemistry Impact factor: 1.783, year: 2002

  9. catena-Poly[[[(2,2′-bipyridine-κ2 N,N′)manganese(II)]-μ-(2,5-dichloro-3,6-dioxocyclo­hexa-1,4-diene-1,4-diolato)-κ4 O 1,O 6:O 3,O 4] ethanol disolvate

    OpenAIRE

    Yuji Nishimura; Akiko Himegi; Akira Fuyuhiro; Shinya Hayami; Satoshi Kawata

    2013-01-01

    The asymmetric unit of the title coordination polymer, {[Mn(C6Cl2O4)(C10H8N2)]·2C2H5OH}n, consists of one MnII ion, one 2,2′-bipyridine (bpy) ligand, one chloranilate (CA2−) ligand and two ethanol solvent molecules. The MnII ion is octahedrally coordinated by two N atoms of one bpy ligand and four O atoms of two chloranilate ions. The chloranilate ion serves as a bridging ligand between the MnII ions, leading to an infinite zigzag chain along [101]. π–π stacki...

  10. catena-Poly[[bis(ethanol-κOmanganese(II]-μ-2,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,4-bis(olato-κ4O1,O6:O3,O4

    Directory of Open Access Journals (Sweden)

    Seiya Tanaka

    2014-03-01

    Full Text Available In the title coordination polymer, [Mn(C6Cl2O4(C2H5OH2]n, the MnII atom and the chloranilate [systematic name: 2,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,4-bis(olate] ion lie on crystallographic inversion centers. The geometry around the MnII atom is a distorted octahedron involving four O atoms of two chloranilate ions and two O atoms from two ethanol molecules. The chloranilate ion serves as a bridging ligand between the MnII ions, leading to an infinite linear chain along the b-axis direction. The chains are linked by O—H...O hydrogen bonds between the apically coordinating ethanol molecule and the chloranilate ion, affording a two-dimensional layer expanding parallel to the ab plane.

  11. catena-Poly[[bis­(ethanol-κO)mangan­ese(II)]-μ-2,5-di­chloro-3,6-di­oxo­cyclo­hexa-1,4-diene-1,4-bis­(olato)-κ4 O 1,O 6:O 3,O 4

    OpenAIRE

    Seiya Tanaka; Akiko Himegi; Tomomi Ohishi; Akira Fuyuhiro; Satoshi Kawata

    2014-01-01

    In the title coordination polymer, [Mn(C6Cl2O4)(C2H5OH)2] n , the MnII atom and the chloranilate [systematic name: 2,5-di­chloro-3,6-dioxo­cyclo­hexa-1,4-diene-1,4-bis­(olate)] ion lie on crystallographic inversion centers. The geometry around the MnII atom is a distorted octa­hedron involving four O atoms of two chloranilate ions and two O atoms from two ethanol mol­ecules. The chloranilate ion serves as a bridging ligand between the MnII ions, leading to an infinite linear chain along the b...

  12. Emprego de reagente em suspensão em sistema de injeção em fluxo: determinação espectrofotométrica de sulfato em águas naturais

    Directory of Open Access Journals (Sweden)

    Crnkovic Paula Manoel

    2002-01-01

    Full Text Available This paper presents an automatic procedure employing a reagent in the form of a slurry in a flow-injection system. The feasibility of the proposal is demonstrated by sulphate determination in water using the Barium Chloranilate method, which is based on the precipitation of barium sulphate. The release of a stoichiometric amount of highly colored chloranilic ions is monitored at 528 nm. The reaction is carried out in alcoholic medium in order to reduce the solubility of the reagent. A considerable improvement in the sensitivity is attained by adding ferric ions to the released chloranilic ions. An on-line filtration step to separate the excess reagent from the released chloranilic ions was necessary. In addition, a column containing a cation exchange resin was included in the manifold to remove potentially interfering ions. The proposed procedure is suitable for 30 determinations per hour and the relative standard deviation is less than 2%. The analytical curve is linear between 0.0 and 40 mg L-1 and the determination limit is about 2.0 mg L-1SO4(2-. Accuracy was confirmed by running several samples already analysed by a standard turbidimetric procedure.

  13. Behavior of charge-transfer absorption upon passing through the neutral-ionic phase transition

    DEFF Research Database (Denmark)

    Jacobsen, Claus Schelde; Torrance, J. B.

    1983-01-01

    The charge-transfer band is determined from reflectance measurements on single crystals of TTF-chloranil from 300 to 45 K, passing through the neutral-ionic phase transition at 84 K. As the temperature is decreased from 300 K toward the transition, hnuCT decreases slowly from 0.66 to 0.55 e...

  14. Synthesis and Antibacterial Activity of 3-( 5-Methylisoxazol-3-yl) - 1,2,4-triazolo [3,4- b ]-1,3,4-thiadiazine Derivatives

    Institute of Scientific and Technical Information of China (English)

    惠新平; 许鹏飞; 王勤; 张琪; 张自义

    2001-01-01

    The condensed products 2—10 of 4-amino-5-mercapto-3-(5methylisoxazol-3-yl)-1,2,4-triazole (1) with chloroacetaldehyde, 2-bromocyclohexanone, chloranil, ω-bromo-ω-(1H-1,2,4-triazol-1-yl)acetophenone, 2-bromo-4'-substituted acetophenones and 2-bromo-6'-methoxy-2'-acetonaphthone were described. The antibacterial activities were also evaluated.

  15. Spectroscopic and computational investigations on the origin of charge transfer between included neutral guest molecules and a functionalized anionic layered host.

    Science.gov (United States)

    Dutta, Dipak; Tummanapelli, Anil Kumar

    2016-08-10

    Layered double hydroxides (LDHs) or anionic clays are an important class of ion-exchange materials, well known for drug and gene delivery and several other applications including catalysis, bioactive nanocomposite, electroactive and photoactive materials. Their structure is based on positively charged brucite-like inorganic sheets with the interlamellar space being occupied by charge-compensating exchangeable anions. In spite of having a vast scope many of the applications of LDHs are restricted as their host-guest chemistry is limited to ion-exchange reactions. Recently we have shown for the first time that charge-transfer interactions can be used as a driving force for the insertion of neutral guest molecules (ortho- and para-chloranil) within the galleries of an Mg-Al LDH by forming a charge-transfer complex with aniline pre-intercalated as p-aminobenzoate anion. Here, we have performed quantum chemical calculations in combination with molecular dynamics simulations to elucidate the nature of interactions, arrangement and the evaluation of electronic and Raman spectral signatures of the chloranil charge-transfer complex included within the galleries of the Mg-Al LDH. The natural bond orbital (NBO) analysis has been used to understand the nature and origin of the unidirectional charge-transfer that lead to the unusual insertion of chloranil in the galleries of the Mg-Al LDH. The NBO analysis reveals that a considerable amount of electronic charge redistribution occurs from the p-aminobenzoate to the chloranil during latter's insertion within the LDH galleries with a very negligible amount of back donation. This work is expected to pave the way for understanding the host-guest chemistry and targeted and controlled delivery of poorly soluble drugs. PMID:27461409

  16. Efficient production of aromatic cation radicals by irradiation with visible light. Utilization of 60C as photocatalyst

    International Nuclear Information System (INIS)

    Complete text of publication follows. Photoinduced electron transfer reactions of fullerenes have of widespread interest because of their potential application in the initiation of chemical processes. The high stability, broad range of visible absorption of 60C as well as the efficient formation and long lifetime of the triplet excited state facilitate its implementation as light harvester. The remarkable ability of the 60C to accept electron have stimulated a number of studies, however, the data concerning the participation of the triplet 60C as electron donor are scarce and formation of 60C+ cation radical has not been detected in photoinduced reactions with strong electron acceptors such as tetracyanoethylene tetracyanoquinodimethane or chloranil. We now report a laser flash photolysis study of triplet 60C quenching by chloranil and demonstrate that addition of trifluoroacetic acid (TFA) results in several orders of magnitude increase in reaction rate. The large rate enhancement is attributed to development of a local polar environment by the preferential solvation of chloranil with TFA. 60C+ cation radical and semiquinone radical are clearly identified as reaction products. The quantum yield of radical formation is found to be as high as 0.80 in the presence of 0.5 M TFA indicating that the efficient protonation of the chloranil radical anion, formed in the primary electron transfer, competes effectively with the back electron transfer process. Because of its high oxidation potential (1.76 V vs. SCE in benzonitrile) 60C+ cation radical readily oxidizes aromatic compounds e.g. fluoranthene, naphthalene derivatives in secondary electron transfer process. Therefore, 60C is a very efficient photocatalyst for production of aromatic cation radicals by irradiation with visible light

  17. Bis(2-{[3-methyl-4-(2,2,2-trifluoroethoxy-2-pyridyl]methylsulfanyl}-1H,3H+-benzimidazolium 2,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,4-diolate

    Directory of Open Access Journals (Sweden)

    Q. N. M. Hakim Al-arique

    2010-06-01

    Full Text Available The title salt, 2C16H15F3N3OS+·C6Cl2O42−, is composed of two independent cations of a lansoprazole {systematic name 2-([3-methyl-4-(2,2,2-trifluoroethoxypyridin-2-yl]methylsulfinyl-1H-benzo[d]imidazole} intermediate and a dianion of chloranilic acid. In the cations of the lansoprazole intermediate, the dihedral angles between the least-squares planes of the pyridine and benzimidazole rings are 11.1 (6 and 13.1 (5°, respectively. The dihedral angles between the mean plane of the benzene ring in the chloranilic acid dianion and the pryidine and benzimidazole rings of the two lansoprazole intermediate groups are 71.8 (1/80.5 (7 and 74.2 (4/74.8 (6°. In addition to ionic bond interactions, the lansoprazole intermediate and chloranilic ions are connected by strong N—H...O hydrogen bonds, which produce a set of extended O—H...O—H...O—H chains along the b axis in the (011 plane. In addition, weak C—H...O, C—H...F, N—H...Cl and π–π [centroid–centroid distances = 3.5631 (15, 3.8187 (13, 3.7434 (17 and 3.842 (2 Å] intermolecular interactions are observed, which contribute to crystal packing stability.

  18. catena-Poly[[[(2,2′-bipyridine-κ2N,N′manganese(II]-μ-(2,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,4-diolato-κ4O1,O6:O3,O4] ethanol disolvate

    Directory of Open Access Journals (Sweden)

    Yuji Nishimura

    2013-02-01

    Full Text Available The asymmetric unit of the title coordination polymer, {[Mn(C6Cl2O4(C10H8N2]·2C2H5OH}n, consists of one MnII ion, one 2,2′-bipyridine (bpy ligand, one chloranilate (CA2− ligand and two ethanol solvent molecules. The MnII ion is octahedrally coordinated by two N atoms of one bpy ligand and four O atoms of two chloranilate ions. The chloranilate ion serves as a bridging ligand between the MnII ions, leading to an infinite zigzag chain along [101]. π–π stacking interactions [centroid–centroid distance = 4.098 (2 Å] is observed between the pyridine rings of adjacent chains. The ethanol molecules act as accepters as well as donors for O—H...O hydrogen bonds, and form a hydrogen-bonded chain along the a axis. The H atoms of the hydroxy groups of the two independent ethanol molecules are each disordered over two sites with equal occupancies.

  19. DEVELOPMENT OF NEW VISIBLE SPECTROPHOTOMETRIC METHODS FOR THE DETERMINATION OF CINITAPRIDE IN PHARMACEUTICAL DOSAGE FORMS

    OpenAIRE

    Ch.V. Suresh; G. Vidya Sagar

    2011-01-01

    Three simple and sensitive Spectrophotometric methods have been developed for the determination of Cinitapride (CNP) in pure and pharmaceutical dosage forms. Method A is based on the formation of charge transfer complex of the drug with chloranilic acid (max : 550 nm). Method B is based on oxidative coupling of the drug with 3-methyl-2-benzothiazolinone hydrazone (max : 420 nm). Method C is based on oxidation followed by complex formation with 1, 10-Phenanthroline (PTL) in the presence of f...

  20. DEVELOPMENT OF NEW VISIBLE SPECTROPHOTOMETRIC METHODS FOR THE DETERMINATION OF CINITAPRIDE IN PHARMACEUTICAL DOSAGE FORMS

    Directory of Open Access Journals (Sweden)

    Ch.V. Suresh

    2011-06-01

    Full Text Available Three simple and sensitive Spectrophotometric methods have been developed for the determination of Cinitapride (CNP in pure and pharmaceutical dosage forms. Method A is based on the formation of charge transfer complex of the drug with chloranilic acid (max : 550 nm. Method B is based on oxidative coupling of the drug with 3-methyl-2-benzothiazolinone hydrazone (max : 420 nm. Method C is based on oxidation followed by complex formation with 1, 10-Phenanthroline (PTL in the presence of ferric chloride to form a colored chromogen (max : 510 nm. These methods have been statistically evaluated and found to be precise and accurate.

  1. Spectroscopy of charge transfer complexes of four amino acids as organic two-dimensional conductors

    Energy Technology Data Exchange (ETDEWEB)

    Padhiyar, Ashvin; Patel, A J; Oza, A T [Department of Physics, Sardar Patel University, Vallabh Vidyanagar-388 120, Gujarat (India)

    2007-12-05

    It is found in this study that four amino acids, namely asparagine, arginine, histidine and glutamine form two-dimensional conducting systems which are charge transfer complexes (CTCs) with organic acceptors like TCNQ, TCNE, chloranil, DDQ, TNF and iodine. It is verified using optical absorption edges that these are 2d conductors like transition metal dichalcogenides obeying absorption functions different from 1d and 3d conductors. This 2d nature is related to the network of intermolecular H-bonding in these complexes, which leads to a global H-bonded network resulting in the absence of local deformation due to the relaxation of strain.

  2. Development of a novel 96-microwell assay with high throughput for determination of olmesartan medoxomil in its tablets

    OpenAIRE

    Darwish Ibrahim A; Wani Tanveer A; Khalil Nasr Y.; Al-Shaikh Abdul-Aziz; Al-Morshadi Najm

    2012-01-01

    Abstract A novel 96-microwell-based spectrophotometric assay has been developed and validated for determination of olmesartan medoxomil (OLM) in tablets. The formation of a colored charge-transfer (CT) complex between OLM as a n-electron donor and 2, 5-dichloro-3, 6-dihydroxy-1, 4-benzoquinone (p-chloranilic acid, pCA) as a π-electron acceptor was investigated, for the first time, and employed as a basis in the development of the proposed assay. The proposed assay was carried out in 96-microw...

  3. Soft Phonon and Central Peak Scattering in Molecular Crystal System

    DEFF Research Database (Denmark)

    Ellenson, W. D.; Kjems, Jørgen

    1977-01-01

    Elastic and inelastic neutron scattering has been used to study the continuous structural transition in chloranil at Tc=90.3 K. The transition results in a doubling of the monoclinic unit cell along the c axis and the molecular displacements correspond to a staggered rotation, ϕ, about axes...... perpendicular to the molecular planes. The temperature dependence of the order parameter, ϕ, has been determined from superlattice Bragg intensities with the result ϕ∝ (Tc−T)0.33±0.02 for 0.005<(1−T/Tc)...

  4. Sur la mise en oeuvre de composés de coordination tétraédriques pour l'élaboration d'architectures supramoléculaires nanoporeuses : synthèse, caractérisation et propriétés zéolitiques d'édifices hétérométalliques ou hybrides

    OpenAIRE

    Imaz, Inhar

    2005-01-01

    The preparation of micro-porous metal-organic frameworks has been envisaged by assemblage of pre-formed tetrahedral coordination compounds involved as primary building units. A typical example of such a building block is (M(oxalate)4)4- (with M = UIV, ZrIV, etc...) but the tetrahedral (Zr(chloranilate)4)4- and (Zr(dihydrobenzoquinolate)4)4- complexes have been envisaged as well. Their assemblage with either metal ions by the means of coordination bonds or organic cations through charge-assist...

  5. Utilization of charge-transfer complexation for the detection of carcinogenic substances in foods: Spectroscopic characterization of ethyl carbamate with some traditional π-acceptors

    Science.gov (United States)

    Adam, Abdel Majid A.; Refat, Moamen S.; Saad, Hosam A.

    2013-04-01

    The study of toxic and carcinogenic substances in foods represents one of the most demanding areas in food safety, due to their repercussions for public health. One potentially toxic compound for humans is ethyl carbamate (EC). EC is a multi-site genotoxic carcinogen of widespread occurrence in fermented foods and alcoholic beverages. Structural and thermal stability of charge-transfer complexes formed between EC as a donor with quinol (QL), picric acid (PA), chloranilic acid (CLA), p-chloranil (p-CHL) and 1,3-dinitrobenzene (DNB) as acceptors were reported. Elemental analysis (CHN), electronic absorption spectra, photometric titration, IR, and 1H NMR spectra show that the interaction between EC and acceptors was stabilized by hydrogen bonding, via a 1:1 stoichiometry. Thermogravimetric (TG) analysis indicates that the formation of molecular CT complexes was stable, exothermic and spontaneous. Finally, the CT complexes were screened for their antibacterial and antifungal activities. The results indicated that the [(EC)(QL)] complex exhibited strong antimicrobial activities against various bacterial and fungal strains compared with standard drugs.

  6. Synthesis of 1,3,4-Thiadiazole, 1,3,4-Thiadiazine, 1,3,6-Thiadiazepane and Quinoxaline Derivatives from Symmetrical Dithiobiureas and Thioureidoethylthiourea Derivatives

    Directory of Open Access Journals (Sweden)

    A. Abou-Zied

    2005-08-01

    Full Text Available Reactions of N,N`-disubstituted hydrazinecarbothioamides 8a-c and substituted thioureidoethylthioureas 9a-c with 2,3,5,6-tetrachloro-1,4-benzoquinone (chloranil, 10a and 2,3,5,6-tetrabromo-1,4-benzoquinone (bromanil, 10b to form N,N`-disubstituted [1,3,4]thiadiazole-2,5-diamines 11a-c, 6,7-dichloro-3-substituted amino-1H-benzo[1,3,4]- thiadiazine-5,8-diones 12a-c, 2,3,7,8-tetrahalothianthrene-1,4,6,9-tetraones 13a,b, 5,6,8- trihalo-7-oxo-3,7-dihydro-2H-quinoxaline-1-carbothioic acid substituted amides 14a-c, 15a-c and 7-substituted imino-[1,3,6]thiadiazepane-3-thiones 16a-c are reported. Rationales for the observed conversions are presented.

  7. Synthesis of 1,3,4-Thiadiazole, 1,3,4-Thiadiazine, 1,3,6-Thiadiazepane and Quinoxaline Derivatives from Symmetrical Dithiobiureas and Thioureidoethylthiourea Derivatives

    OpenAIRE

    Abou-Zied, A.; K. El-Shaieb; A. Mourad; Hassan, A

    2005-01-01

    Reactions of N,N`-disubstituted hydrazinecarbothioamides 8a-c and substituted thioureidoethylthioureas 9a-c with 2,3,5,6-tetrachloro-1,4-benzoquinone (chloranil, 10a) and 2,3,5,6-tetrabromo-1,4-benzoquinone (bromanil, 10b) to form N,N`-disubstituted [1,3,4]thiadiazole-2,5-diamines 11a-c, 6,7-dichloro-3-substituted amino-1H-benzo[1,3,4]- thiadiazine-5,8-diones 12a-c, 2,3,7,8-tetrahalothianthrene-1,4,6,9-tetraones 13a,b, 5,6,8- trihalo-7-oxo-3,7-dihydro-2H-quinoxaline-1-carbothioic acid substit...

  8. New method for spectrophotometric determination of quinones and barbituric acid through their reaction. A kinetic study

    Science.gov (United States)

    Medien, H. A. A.

    1996-11-01

    A new and sensitive spectrophotometric method is described for the determination of p-benzoquinone, p-chloranil and 1.4-naphthoquinone. The method is based on the reaction between quinones and barbituric acid, by which a color is developed with maximum absorption between 485 and 555 nm in 50% methyl alcohol-water mixture. The absorption of the product obeys Beer's law within the concentration range 0.025-05 mM of orginal quinone. The kinetics of the reaction between p-benzoquinone and barbituric acid was studied in a range of methyl alcohol-water mixtures. The reaction follows overall second order kinetics, first order in each of the reactants. The rate increases with increasing dielectric constant. The method was applied for determination of barbituric acid with p-benzoquinone in the concentration range of 0.025-0.345 mM. Other barbiturates do not interfere.

  9. Spectroscopic studies of charge transfer complexes between colchicine and some π acceptors

    Science.gov (United States)

    Arslan, Mustafa; Duymus, Hulya

    2007-07-01

    Charge transfer complexes between colchicine as donor and π acceptors such as tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano- p-benzoquinone (DDQ), p-chloranil ( p-CHL) have been studied spectrophotometrically in dichloromethane at 21 °C. The stoichiometry of the complexes was found to be 1:1 ratio by the Job method between donor and acceptors with the maximum absorption band at a wavelength of 535, 585 and 515 nm. The equilibrium constant and thermodynamic parameters of the complexes were determined by Benesi-Hildebrand and van't Hoff equations. Colchicine in pure form and in dosage form was applied in this study. The formation constants for the complexes were shown to be dependent on the structure of the electron acceptors used.

  10. Determinação espectrofotométrica de citrato de sildenafil em formulações farmacêuticas Spectrophotometric determination of sildenafil citrate in pharmaceutical formulations

    Directory of Open Access Journals (Sweden)

    Patrícia Los Weinert

    2008-01-01

    Full Text Available This paper describes a simple and rapid spectrophotometric method for quantitative determination of sildenafil citrate based on its reaction with p-chloranil accelerated by hydrogen peroxide, producing a stable purple compound (λmax= 535 nm. In the absence of peroxide this reaction is very slow. The experimental conditions were optimized by using response surface methodologies. Beer's law is obeyed in a concentration range of 8.52 x 10-5 - 1.70 x 10-3 mol L-1 (r = 0.999. The detection limit was 1.96 x 10-5 mol L-1. The method was successfully applied for the determination of sildenafil citrate in medicines with good accuracy and precision.

  11. Synthesis, crystal structure, and charge-transfer complexes of TTF derivatives having two imidazole hydrogen-bonding units

    International Nuclear Information System (INIS)

    New hydrogen-bond functionalized tetrathiafulvalene (TTF) derivatives (1 and 2) having two imidazole moieties, which are attached to TTF at the 2- and 4-positions in the imidazole ring, respectively, were synthesized. Electrochemical measurements indicated that the introduction of imidazole moieties at 2- or 4-positions slightly reduced or enhanced the electron-donating ability of TTF. In the crystal structure of 1, N-H...N hydrogen-bonds of the imidazole ring formed a two-dimensional sheet, and further π-stacks on the TTF skeleton built up a one-dimensional column. Mixing 1 with electron-acceptors afforded fully ionic charge-transfer complexes having a 1:1 donor-acceptor ratio, while complex formation of 2 with tetracyanoquinodimethane and p-chloranil yielded partial charge-transfer complexes showing semiconducting behaviors (room temperature conductivities=10-3-10-2 S cm-1).

  12. Synthesis and characterization of mibolerone

    Institute of Scientific and Technical Information of China (English)

    YANG Qing; FAN Bo-lin; TANG Rui-ren

    2007-01-01

    A simple and effective route for the synthesis of mibolerone was described starting from the estr-5(10)-en-3,17-dione in four steps with the overall yield of 47.0%. Thus, two methods for key intermediate methylnorandrost were investigated: one(method A) starting from estr-4-en-3,17-dione underwent 3-keto group protected with ethyl orthoformate to give 3-ethoxy-3,5-dien-estr-17-one, the other(method B) from estr-5(10)-en-3,17-dione and protected 3-keto group to give 3,3-dimethoxy-estr-5(10)-7-one in a mild acidic condition. Then, two intermediates were subsequently reacted with methyllithium followed by a mild hydrolytic procedure and gave methylnorandrost with total yield 25.0% and 86.0%, respectively. In the preparation of 6-dehydrogenation product of methylnorandrost, two procedures(method C and method D) were investigated: one was the protected 17α-methyl-17β-hydroxy △3,-5-enol ethers estrendiene brominated and the resulting 6-bromo-19-methylnortestosterone was then immediately dehydrohaloenated to give 6-dehydro-19-methylnortestosterone, the total yield only reaches 36.0%; the other was directly dehydrogenated with chloranil and the yield reaches 75.6% under the optimum conditions: in refluxing tetrahydrofuran,the molar ratio of methylnorandrost to chloranil is 0.66 and reaction time of 5 h. The titled compound and intermediates were characterized by 1H and 13C NMR, IRMS and elemental analysis.

  13. SYNTHESIS, CHARACTERIZATION AND SPECTROSCOPIC INVESTIGATION OF PYRAZINOPORPHYRAZINE NETWORK POLYMER-SUPPORTED METAL (Ⅱ)-BASED CATALYSTS

    Institute of Scientific and Technical Information of China (English)

    H.H.Abdel-Razik; B.H.Asghar; E.Kenawy

    2013-01-01

    Chloranil through condensation reaction with vicinal diamine such as diaminomaleonitrile produced heterocyclic monomer,p-benzoquinonebis[2,3-b; 2',3'-b']pyrazine-5,6-dinitrile.The tetranitrile monomer was cyclo-tetramerised using lithium/pentanol and acetic acid affording the corresponding tetra p-benzoquinone bis[2,3-b; 2',3'-b']pyrazinoporphyrazine)]-based network polymer (2H-Pz).The tetranitril monomer was cyclo-tetramerised using metal salt and quinoline affording the corresponding porphyrazinato-metal Ⅱ-based network polymers (M-Pz),M =Co,Ni or Cu.Elemental analytical results,IR and NMR spectral data of the prepared molecules are consistent with their assigned formulations.Molecular masses and metal contents of the synthesized polymers proved to be of high molecular masses which confirm the efficiency of tetramerization polymerization and complexation reactions.The prepared pyrazinoporphyrazines were used as efficient catalysts for the oxidation of thiophenol and benzylthiol to their disulfides in the presence of air atmosphere.The results of oxidation of thiophenol and benzylthiol show that after 15 min the maximum yield of the corresponding disulfides reached 95%,91%,respectively.

  14. Rapid and sensitive spectrofluorimetric determination of enrofloxacin, levofloxacin and ofloxacin with 2,3,5,6-tetrachloro- p-benzoquinone

    Science.gov (United States)

    Ulu, Sevgi Tatar

    2009-06-01

    A highly sensitive spectrofluorimetric method was developed for the first time, for the analysis of three fluoroquinolones (FQ) antibacterials, namely enrofloxacin (ENR), levofloxacin (LEV) and ofloxacin (OFL) in pharmaceutical preparations through charge transfer (CT) complex formation with 2,3,5,6-tetrachloro- p-benzoquinone (chloranil,CLA). At the optimum reaction conditions, the FQ-CLA complexes showed excitation maxima ranging from 359 to 363 nm and emission maxima ranging from 442 to 488 nm. Rectilinear calibration graphs were obtained in the concentration range of 50-1000, 50-1000 and 25-500 ng mL -1 for ENR, LEV and OFL, respectively. The detection limit was found to be 17 ng mL -1 for ENR, 17 ng mL -1 for LEV, 8 ng mL -1 for OFL, respectively. Excipients used as additive in commercial formulations did not interfere in the analysis. The method was validated according to the ICH guidelines with respect to specificity, linearity, accuracy, precision and robustness. The proposed method was successfully applied to the analysis of pharmaceutical preparations. The results obtained were in good agreement with those obtained using the official method; no significant difference in the accuracy and precision as revealed by the accepted values of t- and F-tests, respectively.

  15. Solar UV-assisted sample preparation of river water for ultra-trace determination of uranium by adsorptive stripping voltammetry

    International Nuclear Information System (INIS)

    The article describes how solar ultraviolet-A radiation can be used to digest samples as needed for voltammetric ultratrace determination of uranium(VI) in river water. We applied adsorptive stripping voltammetry (AdSV) using chloranilic acid as the complexing agent. Samples from the river Warnow in Rostock (Germany) were pretreated with either soft solar UV or wit artificial hard UV from a 30-W source emitting 254-nm light. Samples were irradiated for 12 h, and both methods yielded the same results. We were able to detect around 1 μg.L-1 of uranium(VI) in a sample of river water that also contained dissolved organic carbon at a higher mg.L-1 levels. No AdSV signal was obtained for U(VI) without any UV pre-treatment. Pseudo-polarographic experiments confirmed the dramatic effect of both digestion techniques the the AdSV response. The new method is recommended for use in mobile ultratrace voltammetry of heavy metals for most kinds of natural water samples including tap, spring, ground, sea, and river waters. The direct use of solar radiation for sample pre-treatment represents a sustainable technique for sample preparation that does not consume large quantities of chemicals or energy. (author)

  16. Optimized and Validated Spectrophotometric Methods for the Determination of Enalapril Maleate in Commercial Dosage Forms

    Directory of Open Access Journals (Sweden)

    Sk Manirul Haque

    2008-01-01

    Full Text Available Four simple, rapid and sensitive spectrophotometric methods have been proposed for the determination of enalapril maleate in pharmaceutical formulations. The first method is based on the reaction of carboxylic acid group of enalapril maleate with a mixture of potassium iodate (KIO3 and iodide (KI to form yellow colored product in aqueous medium at 25 ± 1°C .The reaction is followed spectrophotometrically by measuring the absorbance at 352 nm. The second, third and fourth methods are based on the charge transfer complexation reaction of the drug with p-chloranilic acid (pCA in 1, 4-dioxan-methanol medium, 2, 3-dichloro 5, 6-dicyano 1, 4-benzoquinone (DDQ in acetonitrile-1,4 dioxane medium and iodine in acetonitrile-dichloromethane medium. Under optimized experimental conditions, Beer’s law is obeyed in the concentration ranges of 2.5–50, 20–560, 5–75 and 10–200 μg mL−1, respectively. All the methods have been applied to the determination of enalapril maleate in pharmaceutical dosage forms. Results of analysis are validated statistically.

  17. Investigations in the field of solid-state polymerization Pt. 37

    International Nuclear Information System (INIS)

    Chloranil (CA) and bromanil (BA) which have otherwise similar radiation-chemical properties affect the solid state polymerization of acenaphthylene (ACN) in different manner. CA decreases the rate of polymerization proportionally to its concentration and besides, it also decreases the conversion limit and the molecular weight of the product. BA does not influence the reaction up to a conversion of 20%, but soon afterwards the conversion limit of the polymerization is reached. This limit, above 8M% BA content, is independent of the BA concentration. The reason for the different behaviour is that while BA forms an ideal eutectics with ACN, CA forms a solid solution of limited miscibility at the temperature of the experiments. Both pairs of compounds give charge transfer complex in solid state. The charge transfer complex of BA exists merely at the boundary layer of the crystals, but that of CA is within the crystal lattice of ACN as in a solid solvent. In none of the studied cases could be detected the charge transfer complex with its own specific crystal structure. The effect of CA on the solid state polymerization of ACN is discussed on the basis of the results obtained by PPP and CNDO/2 calculations on ACN and CA. (author)

  18. Developing and Stabilizing Analytical Method for the Determination of Uranium in Water Systems using Voltammeters

    International Nuclear Information System (INIS)

    Uranium is a precious metal found in all over the world in trace amounts. The water flowing over the surface dissolves the uranium from surface and rocks coming in contact with it. To determine the uranium concentration in water we emphasized for the development of an analytical method. The development of technique for the uranium determination in water is based on Chloranilic acid (CAA) and Hanging Mercury Drop Electrode (HMDE). CAA is a water soluble compound forms a complex with uranium, which was collected by the physical adsorption of the complex on the electrode. The standard uranium solution was used for calibration. Below pH 2 and above pH 3, the standard deviation exceeded 1 micro g/L. So, the pH for the samples was maintained between 2.3 and 3. The accuracy of the method was established by recovery studies in control samples. Then the developed technique was applied for uranium determination in sea water. Different surfactants were used to minimize the effects of interfering radicals. The effects of potential variation were also examined. The best results were obtained for Sodium Dodecyl Sulfate (SDS). Some problems still existing can be eliminated by the use of inert anti foaming agent. (author)

  19. Flotation-Separation of the Pollutant Species of Chromium, Cadmium and Lead from aqueous Solutions and Natural Waters

    International Nuclear Information System (INIS)

    This work aims to present simple, rapid and accurate procedures to recover the pollutant species of chromium, cadmium and lead from different types of water using the flotation technique. To achieve this goal, precipitate flotation was the method of choice for this investigation using oleic acid (HOL) as a surfactant. Cr(III) as its hydroxide and Cr(VI) as Ag2CrO4 or Ag2Cr2O7 are removed in 6.5±0.2 and 6-75 ph range, respectively. 2,4,6-Tri(2-pyridyl)-1,3,5-triazine (TPTA), in the presence of KI, is a good collector for quantitative separation of trace amounts of Cd(II) in the ph range 6-7.5. Chloranilic acid (CAA) is found to be the most effective complexing agent for the flotation of trace amounts of Pb(II) over the ph range 4-7. The effects of surfactant and analyte concentrations, foreign ions and temperature have been examined. The application of this procedure to recover these analytes added to natural samples has been investigated. Also, a procedure for sective separation of Cr(III) from Cr(VI) either in aqueous solutions or in saline water is proposed. Moreover, a mechanism of flotation is suggested

  20. Spectrophotometric kinetic and determination of quinones and barbiturates

    Science.gov (United States)

    Medien, H. A. A.; Zahran, A. A.

    2001-10-01

    The kinetics of 1,3-dimethylbarbituric acid with some quinones, namely 1,4-benzoquinone, 1,4-naphthoquinone and p-chloranil in 50% methyl alcohol-water mixture have been investigated spectrophotometrically at 30-50°C. The reaction follows overall second-order kinetics, first order each in reactant. From the dependence of the rate constants on temperature, activation parameters have been calculated. A plot of Δ H# versus Δ S# for the reaction gave a good straight line with an isokinetic temperature of 387.66 K. The rate of reaction increases with increasing dielectric constant of the medium. Based on this reaction, a spectrophotometric determination method of quinones is described. Beer's law was obeyed within the concentration range 2.7-61.5 μg ml -1 quinone. The method was applied for determination of barbituric, thiobarbituric and 1,3-dimethylbarbituric acids with 1,4-naphthoquinone within a concentration range of 3.2-39.5 μg ml -1 barbiturate. The reaction mechanism and reactivity have been discussed.

  1. Interaction of 2-aminopyrimidine with σ- and π-acceptors involving chemical reactions via initial charge transfer complexation

    Science.gov (United States)

    Rabie, U. M.; Abou-El-Wafa, M. H.; Mohamed, R. A.

    2007-12-01

    Interaction of 2-aminopyrimidine (AP) with iodine as a typical σ-type acceptor and with a typical π-type acceptor, 2,3,5,6-tetrachloro-1,4-benzoquinone, p-chloranil (CHL) have been studied spectrophotometrically. Electronic absorption spectra of the system AP-I 2 in several organic solvents of different polarities have performed clear charge transfer (CT) band(s). Formation constants ( KCT) and molar absorption coefficients ( ɛCT) and thermodynamic properties, Δ H, Δ S, and Δ G, of this system in various organic solvents were determined and discussed. Interaction of AP with the π-acceptor has shown unique behaviors. Chemical reaction has occurred via prior or initial formation of the outer-sphere CT complex followed by formation of the corresponding anion radicals, CHL rad - , as intermediates. UV-vis, 1H NMR, Mass, and FT-IR spectra in addition to the elemental analysis were used to confirm the proposed occurrence of the chemical reaction and to investigate the synthesized solid products.

  2. Probing near-interface ferroelectricity by conductance modulation of a nano-granular metal

    Science.gov (United States)

    Huth, M.; Rippert, A.; Sachser, R.; Keller, L.

    2014-12-01

    The electronic functionality of thin films is governed by their interfaces. This is very important for the ferroelectric (FE) state which depends on thin-film clamping and interfacial charge transfer. Here we show that in a heterostructure consisting of a nano-granular metal and an organic FE layer of [tetrathiafulvalene]+δ [p-chloranil]-δ the nano-granular layer's conductance provides a sensitive and non-invasive probe of the temperature-dependent dielectric properties of the FE layer. We provide a theoretical framework that is able to qualitatively reproduce the observed conductance changes taking the anisotropy of the dielectric anomaly at the paraelectric-FE phase transition into account. The approach is also suitable for observing dynamical effects close to the phase transition. Focused electron beam induced deposition as fabrication method for the nano-granular metal guarantees excellent down-scaling capabilities, so that monitoring the FE state on the lateral scale down to 20-30 nm can be envisioned.

  3. Probing near-interface ferroelectricity by conductance modulation of a nano-granular metal

    International Nuclear Information System (INIS)

    The electronic functionality of thin films is governed by their interfaces. This is very important for the ferroelectric (FE) state which depends on thin-film clamping and interfacial charge transfer. Here we show that in a heterostructure consisting of a nano-granular metal and an organic FE layer of [tetrathiafulvalene]+δ[p-chloranil]−δ the nano-granular layer's conductance provides a sensitive and non-invasive probe of the temperature-dependent dielectric properties of the FE layer. We provide a theoretical framework that is able to qualitatively reproduce the observed conductance changes taking the anisotropy of the dielectric anomaly at the paraelectric–FE phase transition into account. The approach is also suitable for observing dynamical effects close to the phase transition. Focused electron beam induced deposition as fabrication method for the nano-granular metal guarantees excellent down-scaling capabilities, so that monitoring the FE state on the lateral scale down to 20–30 nm can be envisioned. (paper)

  4. Glutathione S-transferase in aquatic macro-invertebrates and its interaction with different organic micropollutants

    Energy Technology Data Exchange (ETDEWEB)

    Dierickx, P.J.

    1984-12-01

    In higher organisms, glutathione S-transferase (GST) plays a key role in the detoxification of a large number of xenobiotics. In the present work the presence of GST in aquatic macro-invertebrates and its possible significance as a detoxification mechanism of organic micropollutants in the aquatic environment is investigated. So far, GST has been found in 20 macro-invertebrates (in adults as well as in larvae) and in insects as well as in other animal groups. The GST activities were relatively high, ranging from 10 to 600% of the activity found in rat liver. The interaction of quinones, o-chloranil and chlorophenoxyalkyl acids with the GST activity, in extracts from three different macro-invertebrates, revealed an inhibition which was quite similar to that previously found for rat liver GST. In Tubifex tubifex extracts at least three different GST isoenzymes could be demonstrated. These partially purified isoenzymes were used for the kinetic analysis of GST inhibition by 2,4-dichlorophenoxyalkyl acid and 1,4-benzoquinone, using Lineweaver--Burk plots. The same kinetic patterns were observed as for rat liver GST. The results demonstrate that the interactions of the compounds investigated with aquatic macro-invertebrate and with rat liver GST are in very good agreement. It is concluded that macro-invertebrate GST can play a key role in the detoxification of organic micropollutants in the aquatic environment.

  5. Phytochemical profiles and antioxidant activities in six species of ramie leaves.

    Directory of Open Access Journals (Sweden)

    Yongsheng Chen

    Full Text Available Increased consumption of vegetables or plant food has been associated with decreased risk of developing major chronic diseases, such as cancers, diabetes, cardiovascular diseases, and age-related functional decline. Ramie leaves are rich in phenolics and flavonoids, which have been suggested for human health benefits. Phenolic contents, flavonoid contents, phenolic compounds, and anti-cancer properties in six species of ramie leaves were analyzed by Folin-reagent method, sodium borohydride/chloranil-based assay (SBC, HPLC method and antiproliferation, cytoxicity, respectively. Antioxidant activities were measured through peroxyl radical scavenging capacity (PSC method, oxygen radical absorbance capacity (ORAC method, and cellular antioxidant activity (CAA. Research indicated that Boehmeria penduliflora contained the highest total phenolic content (2313.7±27.28 mg GAE/100 g FW, and flavonoid content (1682.4±27.70 mg CAE/100 g FW. Boehmeria tricuspis showed the highest PSC value (9574.8±117.63 µM vit. C equiv./100 g FW, while Boehmeria penduliflora indicated the highest ORAC value (330.44±16.88 µmol Trolox equiv./g FW. The antioxidant activities were correlated with phenolic contents and flavonoid contents. Boehmeria tricuspis had the highest antiproliferative capacity with the lowest EC₅₀ (4.11±0.19 mg/mL. The results for the analyzed ramie for CAA were significantly different from each other (p<0.05, Boehmeria tricuspis had the highest CAA value (133.63±7.10 µmol QE/100 g. Benzoic acid, 4-coumaric acid, caffeic acid, and ferulic acid were the dominant phenolic ingredients in the ramie leaves according to HPLC analysis. Our research is the first report to study the phytochemical profiles and antioxidant activities in different species of ramie leaves for their health benefit.

  6. Validated spectrophotometric methods for determination of some oral hypoglycemic drugs.

    Science.gov (United States)

    Farouk, M; Abdel-Satar, O; Abdel-Aziz, O; Shaaban, M

    2011-02-01

    Four accurate, precise, rapid, reproducible, and simple spectrophotometric methods were validated for determination of repaglinide (RPG), pioglitazone hydrochloride (PGL) and rosiglitazone maleate (RGL). The first two methods were based on the formation of a charge-transfer purple-colored complex of chloranilic acid with RPG and RGL with a molar absorptivity 1.23 × 103 and 8.67 × 102 l•mol-1•cm-1 and a Sandell's sensitivity of 0.367 and 0.412 μg•cm-2, respectively, and an ion-pair yellow-colored complex of bromophenol blue with RPG, PGL and RGL with molar absorptivity 8.86 × 103, 6.95 × 103, and 7.06 × 103 l•mol-1•cm-1, respectively, and a Sandell's sensitivity of 0.051 μg•cm-2 for all ion-pair complexes. The influence of different parameters on color formation was studied to determine optimum conditions for the visible spectrophotometric methods. The other spectrophotometric methods were adopted for demtermination of the studied drugs in the presence of their acid-, alkaline- and oxidative-degradates by computing derivative and pH-induced difference spectrophotometry, as stability-indicating techniques. All the proposed methods were validated according to the International Conference on Harmonization guidelines and successfully applied for determination of the studied drugs in pure form and in pharmaceutical preparations with good extraction recovery ranges between 98.7-101.4%, 98.2-101.3%, and 99.9-101.4% for RPG, PGL, and RGL, respectively. Results of relative standard deviations did not exceed 1.6%, indicating that the proposed methods having good repeatability and reproducibility. All the obtained results were statistically compared to the official method used for RPG analysis and the manufacturers methods used for PGL and RGL analysis, respectively, where no significant differences were found. PMID:22466095

  7. Analytical study for the charge-transfer complexes of losartan potassium

    Energy Technology Data Exchange (ETDEWEB)

    Darwish, Ibrahim A. [Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Assiut University, Assiut 71526 (Egypt)]. E-mail: iadarwish@yahoo.com

    2005-09-06

    Studies were carried out, for the first time, to investigate the charge-transfer reactions of losartan potassium (LOS-K) as n-electron donor with the {sigma}-acceptor iodine and various {pi}-acceptors: 7,7,8,8-tetracyanoquinodimethane, 1,3,5-trinitrobenzene, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, p-chloranilic acid, tetracyanoethylene, 2,3,5,6-tetrabromo-1,4-benzoquinone, 2,3,5,6-tetrachloro-1,4-benzoquinone, and 2,4,7-trinitro-9-fluorenone. Different colored charge-transfer complexes and radical anions were obtained. Different variables affecting the reactions were studied and optimized. The formed complexes and the site of interaction were examined by UV-vis, IR, and {sup 1}H NMR techniques, and computational molecular modeling. The formation of the colored complexes were utilized in the development of simple, rapid and accurate spectrophotometric methods for the analysis of LOS-K in pure form as well as in its pharmaceutical tablets. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9985-0.9998) were found between the absorbances and the concentrations of LOS-K in the range of 2-200 {mu}g ml{sup -1}. The limits of assays detection ranged from 0.61 to 19.65 {mu}g ml{sup -1}. No interference could be observed from the co-formulated hydrochlorothiazide (HCTZ), as well as from the additives commonly present in the tablets. The methods were successfully applied to the analysis of tablets from different manufacturers that contain LOS-K, alone or combined with HCTZ, with good accuracy and precision; the recovery percentages ranged from 98.96 {+-} 1.62% to 101.58 {+-} 1.29%. The results were compared favourably with the reported method.

  8. Timeresolved investigation of atomic order in tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) monocrystals after excitation with ultrashort light pulses; Zeitaufgeloeste Untersuchung atomarer Ordnung in Tetrathiafulvalen-Tetracyanochinodimethan (TTF-TCNQ)-Einkristallen nach Anregung mit ultrakurzen Lichtpulsen

    Energy Technology Data Exchange (ETDEWEB)

    Sager, Christian

    2011-02-15

    This thesis describes time-resolved investigations of the atomic structure of one-dimensional organic molecular crystals after laser excitation of the photo-induced phase transition. There is a neutral to ionic phase transition in tetrathiafulvalene-chloranil-crystals (TTF-CA-crystals). At this phase transition a Peierls distortion occurs. A new model is introduced, that can explain the photo-induced phase transition in TTF-CY-crystals. This model is called charge density wave model of photo induced structural phase transition. There is a structural phase transition in tetrathiafulvalene-tetracyanochinodimethane-crystals (TTF-TCNQ-crystals). At this phase transition the one-dimensional metal TTF-TCNQ is transformed to an insulator. The phase transition is driven by the Peierls distortion. The charge density wave model is appropriate for description of the processes in TTF-TCNQ-crystals after laser excitation. The results of time-resolved measurements of the structure of TTF-TCNQ-crystals after excitation of the photo-induced phase transition can be anticipated with the charge density wave model. In the basis of these anticipated results, a time-resolved measurement for investigation of the atomic structure of TTF-TCNQ after excitation of the photo-induced phase transition is proposed. The time-resolved measurement should be performed at a beamline of a third generation synchrotron by the optical pump X-ray probe technique. The time-resolved measurement is prepared by an optical characterization and by static X-ray diffraction measurements. The results of the optical characterization and the static X-ray diffraction measurements are presented and analyzed. (orig.)

  9. Effects of x-ray irradiation on mast cells and mastocalcergy in the connective tissue

    International Nuclear Information System (INIS)

    Experiments were performed to observe the influence of x-ray irradiation on mast cells and mastocalcergy in rats. Animals were irradiated single dose of x-ray. X-ray irradiation was applied to the whole body in doses either 100 rads or 150 rads (Cobalt-60 Teletherapy Unit). One day after irradiation the rats were injected lead acetate intravenously, followed by injection of compound 48/80 in the back subcutaneously. Animals were killed by decapitation at intervals, 1 hour, 5 hours, 1 day and 6 day after subcutaneous injection. Specimens of the abdominal and back skin were fixed in alcohol formol solution and stained with the following methods; H-E for observation of pathological changes of tissues, toluidine blue for demonstration of mast cells, von Kossa-azure A for demonstration of carbonate and phosphate, and chloranilic acid for demonstration of calcium. The following conclusions were obtained. Calciphylatic wheals are large size in the control group, medium size in 100 rads irradiation group and small size in 150 rads irradiation group. In x-ray irradiation groups the number of mast cells decreases more in the 150 rads than in the 100 rads irradiation. In the 100 rads x-ray irradiation group, histochemical study of the injection sites showed that calcium impregnated to mast cell granules and connective tissue fibers in 1 days after subcutaneous injection. The morphogenesis of this calcinosis was the same in the rat of 5 hour after subcutaneous injection of the control group. Whereas, 1 day after subcutaneous injection in 150 rads x-ray irradiation group calcium deposited more slightly than other groups

  10. Spectrophotometric Determination of Some Fluoroquinolone Antibacterials through Charge-transfer and Ion-pair Complexation Reactions

    Energy Technology Data Exchange (ETDEWEB)

    El-Brashy, Amina Mohamed; El-Sayed Metwally Mohamed; El-Sepai, Fawzi Abdallah [University of Mansoura, Mansoura (Egypt)

    2004-03-15

    Two simple, rapid and sensitive spectrophotometric methods for the determination of three fluoroquinolones, namely levofloxacin, norfloxacin and ciprofloxacin have been performed either in pure form or in their tablets. In the first method, levofloxacin and norfloxacin are directly treated with bromocresol green (BCG) in dichloromethane while ciprofloxacin is allowed to react with the same dye in aqueous acidic buffer. Highly yellow colored complex species were formed instantaneously in case of levofloxacin and norfloxacin or after extraction into dichloromethane for ciprofloxacin. The formed complexes are quantified spectrophotometrically at their absorption maxima at 411 nm for levofloxacin and 412 nm for norfloxacin and ciprofloxacin. The second method involves the reaction of levofloxacin with {rho}-chloranilic acid ({rho}-CA) and norfloxacin with tetracyanoethylene (TCNE) in acetonitrile to give complexes with maximum absorbance at 521 and 333 nm for the two drugs, respectively. Adopting the first procedure, calibration graphs were linear over the range 1- 20 {mu}g mL{sup .1} with mean percentage recoveries of 100.41 {+-} 0.72, 99.99 {+-} 0.54 and 100.23 {+-} 0.91 for the three drugs, respectively. For the second procedure, the concentration ranges were 15-250 {mu}g mL{sup .1} for levofloxacin using {rho}-CA and 0.8-16 {mu}g mL{sup .1} for norfloxacin using TCNE with mean percentage recoveries of 99.88 {+-} 0.45 and 100.26 {+-} 0.68 for the two drugs, respectively. The proposed methods were successfully applied to determine these drugs in their tablet formulations and the results compared favorably to that of reference methods. The proposed methods are recommended for quality control and routine analysis

  11. Timeresolved investigation of atomic order in tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) monocrystals after excitation with ultrashort light pulses

    International Nuclear Information System (INIS)

    This thesis describes time-resolved investigations of the atomic structure of one-dimensional organic molecular crystals after laser excitation of the photo-induced phase transition. There is a neutral to ionic phase transition in tetrathiafulvalene-chloranil-crystals (TTF-CA-crystals). At this phase transition a Peierls distortion occurs. A new model is introduced, that can explain the photo-induced phase transition in TTF-CY-crystals. This model is called charge density wave model of photo induced structural phase transition. There is a structural phase transition in tetrathiafulvalene-tetracyanochinodimethane-crystals (TTF-TCNQ-crystals). At this phase transition the one-dimensional metal TTF-TCNQ is transformed to an insulator. The phase transition is driven by the Peierls distortion. The charge density wave model is appropriate for description of the processes in TTF-TCNQ-crystals after laser excitation. The results of time-resolved measurements of the structure of TTF-TCNQ-crystals after excitation of the photo-induced phase transition can be anticipated with the charge density wave model. In the basis of these anticipated results, a time-resolved measurement for investigation of the atomic structure of TTF-TCNQ after excitation of the photo-induced phase transition is proposed. The time-resolved measurement should be performed at a beamline of a third generation synchrotron by the optical pump X-ray probe technique. The time-resolved measurement is prepared by an optical characterization and by static X-ray diffraction measurements. The results of the optical characterization and the static X-ray diffraction measurements are presented and analyzed. (orig.)

  12. 2-Hetaryl-1,3-tropolones based on five-membered nitrogen heterocycles: synthesis, structure and properties.

    Science.gov (United States)

    Sayapin, Yury A; Tupaeva, Inna O; Kolodina, Alexandra A; Gusakov, Eugeny A; Komissarov, Vitaly N; Dorogan, Igor V; Makarova, Nadezhda I; Metelitsa, Anatoly V; Tkachev, Valery V; Aldoshin, Sergey M; Minkin, Vladimir I

    2015-01-01

    A series of derivatives of 2-hetaryl-1,3-tropolone (β-tropolone) was prepared by the acid-catalyzed reaction of 2-methylbenzoxazoles, 2-methylbenzothiazoles and 2,3,3-trimethylindoline with 3,4,5,6-tetrachloro-1,2-benzoquinone. The molecular structures of the three representative compounds were determined by X-ray crystallography. In crystal and (as shown by the DFT PBE0/6-311+G** calculations) in solution, 2-hetaryl-4,5,6,7-tetrachloro- and 2-hetaryl-5,6,7-trichloro-1,3-tropolones exist in the NH-tautomeric form with a strong resonance-assisted intramolecular N-H···O hydrogen bond. The mechanism of the formation of 1,3-tropolones in the reaction of methylene-active five-membered heterocycles with o-chloranil in acetic acid solution has been studied using density functional theory (DFT) methods. The reaction of 2-(2-benzoxa(thia)zolyl)-5,6,7-trichloro(4,5,6,7-tetrachloro)-1,3-tropolones with alcohols leads to the contraction of the seven-membered tropone ring with the formation of 2-(2-benzoxa(thia)zolyl)-6-alkoxycarbonylphenols. The molecular structure of 2-(2-ethoxycarbonyl-6-hydroxy-3,4,5-trichlorophenyl)benzoxazole has been determined by X-ray diffraction. 2-(2-Benzoxa(thia)zolyl)-6-alkoxycarbonylphenols display intense green fluorescence with anomalous Stokes shifts caused by the excited state intramolecular proton transfer (ESIPT) effects. PMID:26664640

  13. Development of a novel 96-microwell assay with high throughput for determination of olmesartan medoxomil in its tablets

    Directory of Open Access Journals (Sweden)

    Darwish Ibrahim A

    2012-01-01

    Full Text Available Abstract A novel 96-microwell-based spectrophotometric assay has been developed and validated for determination of olmesartan medoxomil (OLM in tablets. The formation of a colored charge-transfer (CT complex between OLM as a n-electron donor and 2, 5-dichloro-3, 6-dihydroxy-1, 4-benzoquinone (p-chloranilic acid, pCA as a π-electron acceptor was investigated, for the first time, and employed as a basis in the development of the proposed assay. The proposed assay was carried out in 96-microwell plates. The absorbance of the colored-CT complex was measured at 490 nm by microwell-plate absorbance reader. The optimum conditions of the reaction and the analytical procedures of the assay were established. Under the optimum conditions, linear relationship with good correlation coefficient was found between the absorbance and the concentration of OLM in the range of 1-200 μg ml-1. The limits of detection and quantitation were 0.3 and 1 μg ml-1, respectively. No interference was observed from the additives that are present in the pharmaceutical formulation or from hydrochlorothiazide and amlodipine that are co-formulated with OLM in some formulations. The assay was successfully applied to the analysis of OLM in tablets with good accuracy and precision. The assay described herein has great practical value in the routine analysis of OLM in quality control laboratories, as it has high throughput property, consumes minimum volume of organic solvent thus it offers the reduction in the exposures of the analysts to the toxic effects of organic solvents, and reduction in the analysis cost by 50-fold. Although the proposed assay was validated for OLM, however, the same methodology could be used for any electron-donating analyte for which a CT reaction can be performed.

  14. Spectrophotometric determination of quetiapine fumarate in pharmaceuticals and human urine by two charge-transfer complexation reactions

    Directory of Open Access Journals (Sweden)

    Vinay K.B.

    2012-01-01

    Full Text Available Two simple, rapid and accurate spectrophotometric procedures are proposed for the determination of quetiapine fumarate (QTF in pharmaceuticals and in spiked human urine. The methods are based on charge transfer complexation reactions of free base form of the drug (quetiapine, QTP, as n-electron donor (D, with either p-chloranilic acid (p-CAA (method A or 2,3-dichloro-5,6-dicyanoquinone (DDQ (method B as π-acceptors (A. The coloured charge transfer complexes produced exhibit absorption maxima at 520 and 540 nm, in method A and method B, respectively. The experimental conditions such as reagent concentration, reaction solvent and time have been carefully optimized to achieve the maximum sensitivity. Beer’s law is obeyed over the concentration ranges of 8.0 - 160 and 4.0 - 80.0 μg ml-1, for method A and method B, respectively. The calculated molar absorptivity values are 1.77 × 103 and 4.59 × 103 l mol-1cm-1, respectively, for method A and method B. The Sandell sensitivity values, limits of detection (LOD and quantification (LOQ have also been reported. The stoichiometry of the reaction in both cases was accomplished adopting the limiting logarithmic method and was found to be 1: 2 (D: A. The accuracy and precision of the methods were evaluated on intra-day and inter-day basis. The proposed methods were successfully applied for the determination of QTF in pharmaceutical formulations and spiked human urine.

  15. Quantitative analysis of total retronecine esters-type pyrrolizidine alkaloids in plant by high performance liquid chromatography

    International Nuclear Information System (INIS)

    Pyrrolizidine alkaloids (PAs) are alkaloids which typically contain a necine (7-hydroxy-1-hydroxymethyl-6,7-dihydro-5H-pyrrolizidine) base unit, and they can be found in one third of the higher plants around the world. They are hepatotoxic, mutagenic and carcinogenic and pose a threat to human health and safety. A specific, quick and sensitive method is therefore needed to detect and quantify the PAs sometimes in trace amount in herbs, tea or food products. Based on high performance liquid chromatography with prior derivatization of the alkaloids using o-chloranil and Ehrlich's reagent, we report an improved method for quantitative analysis of the total amount of retronecine esters-type pyrrolizidine alkaloids (RET-PAs) in a plant extract. The total quantitation of RET-PAs is achieved because of a common colored retronecine marker, a 7-ethoxy-1-ethoxylmethyl retronecine derivative, is produced with all the different RET-PAs during the derivatization reaction. The chemical identity of the common retronecine marker was characterized on-line by positive mode electrospray ionization mass spectrometry and nuclear magnetic resonance spectroscopy. The limit of detection using the improved method is 0.26 nmol mL-1 and the limit of quantitation is 0.79 nmol mL-1. The advantages of this method are much enhanced sensitivity in detection and quantitation, and, no restriction on the choice of RET-PA as a calibration standard. Application of the developed method to the quantitation of total RET esters-type PAs in Senecio scandens from different regions of China is also reported

  16. Synthesis and properties of 5,10,15,20-tetrakis[4-(3-N,N-dimethylaminopropoxy)phenyl] chlorin as potential broad-spectrum antimicrobial photosensitizers.

    Science.gov (United States)

    Ferreyra, Darío D; Reynoso, Eugenia; Cordero, Paula; Spesia, Mariana B; Alvarez, M Gabriela; Milanesio, M Elisa; Durantini, Edgardo N

    2016-05-01

    A novel 5,10,15,20-tetrakis[4-(3-N,N-dimethylaminopropoxy)phenyl]chlorin (TAPC) was synthesized by reduction of the corresponding porphyrin TAPP with p-toluenesulfonhydrazide, followed by selective oxidation with o-chloranil. Spectroscopic properties and the photodynamic activity of these photosensitizers were compared in N,N-dimethylformamide. An increase in the absorption band at 650nm was found for the chlorin derivative with respect to TAPP. These photosensitizers emit red fluorescence with quantum yields of 0.15. Both compounds were able to photosensitize singlet molecular oxygen with quantum yields of about 0.5. Also, the formation of superoxide anion radical was detected in the presence of TAPC or TAPP and NADH. Photodynamic inactivation was investigated on a Gram-positive bacterium Staphylococcus aureus, a Gram-negative bacterium Escherichia coli and a fungal yeast Candida albicans cells. In vitro experiments showed that TAPC or TAPP were rapidly bound to microbial cells at short incubation periods. These photosensitizers, without intrinsic positive charges, contain four basic amino groups. These substituents can be protonated at physiological pH, increasing the interaction with the cell envelopment. Photosensitized inactivation improved with an increase of both photosensitizer concentrations and irradiation times. After 15min irradiation, a 7 log reduction of S. aureus was found for treated with 1μM photosensitizer. Similar result was obtained with E. coli after using 5μM photosensitizer and 30min irradiation. Also, the last conditions produced a decrease of 5 log in C. albicans cells. Therefore, TAPC was highly effective as a broad-spectrum antimicrobial photosensitizer. PMID:26994333

  17. Phytochemical profiles and antioxidant activities in six species of ramie leaves.

    Science.gov (United States)

    Chen, Yongsheng; Wang, Gaoyan; Wang, Hong; Cheng, Chaohua; Zang, Gonggu; Guo, Xinbo; Liu, Rui Hai

    2014-01-01

    Increased consumption of vegetables or plant food has been associated with decreased risk of developing major chronic diseases, such as cancers, diabetes, cardiovascular diseases, and age-related functional decline. Ramie leaves are rich in phenolics and flavonoids, which have been suggested for human health benefits. Phenolic contents, flavonoid contents, phenolic compounds, and anti-cancer properties in six species of ramie leaves were analyzed by Folin-reagent method, sodium borohydride/chloranil-based assay (SBC), HPLC method and antiproliferation, cytoxicity, respectively. Antioxidant activities were measured through peroxyl radical scavenging capacity (PSC) method, oxygen radical absorbance capacity (ORAC) method, and cellular antioxidant activity (CAA). Research indicated that Boehmeria penduliflora contained the highest total phenolic content (2313.7±27.28 mg GAE/100 g FW), and flavonoid content (1682.4±27.70 mg CAE/100 g FW). Boehmeria tricuspis showed the highest PSC value (9574.8±117.63 µM vit. C equiv./100 g FW), while Boehmeria penduliflora indicated the highest ORAC value (330.44±16.88 µmol Trolox equiv./g FW). The antioxidant activities were correlated with phenolic contents and flavonoid contents. Boehmeria tricuspis had the highest antiproliferative capacity with the lowest EC₅₀ (4.11±0.19 mg/mL). The results for the analyzed ramie for CAA were significantly different from each other (pphenolic ingredients in the ramie leaves according to HPLC analysis. Our research is the first report to study the phytochemical profiles and antioxidant activities in different species of ramie leaves for their health benefit. PMID:25243741

  18. Spectrophotometric Determination of Some Fluoroquinolone Antibacterials through Charge-transfer and Ion-pair Complexation Reactions

    International Nuclear Information System (INIS)

    Two simple, rapid and sensitive spectrophotometric methods for the determination of three fluoroquinolones, namely levofloxacin, norfloxacin and ciprofloxacin have been performed either in pure form or in their tablets. In the first method, levofloxacin and norfloxacin are directly treated with bromocresol green (BCG) in dichloromethane while ciprofloxacin is allowed to react with the same dye in aqueous acidic buffer. Highly yellow colored complex species were formed instantaneously in case of levofloxacin and norfloxacin or after extraction into dichloromethane for ciprofloxacin. The formed complexes are quantified spectrophotometrically at their absorption maxima at 411 nm for levofloxacin and 412 nm for norfloxacin and ciprofloxacin. The second method involves the reaction of levofloxacin with ρ-chloranilic acid (ρ-CA) and norfloxacin with tetracyanoethylene (TCNE) in acetonitrile to give complexes with maximum absorbance at 521 and 333 nm for the two drugs, respectively. Adopting the first procedure, calibration graphs were linear over the range 1- 20 μg mL.1 with mean percentage recoveries of 100.41 ± 0.72, 99.99 ± 0.54 and 100.23 ± 0.91 for the three drugs, respectively. For the second procedure, the concentration ranges were 15-250 μg mL.1 for levofloxacin using ρ-CA and 0.8-16 μg mL.1 for norfloxacin using TCNE with mean percentage recoveries of 99.88 ± 0.45 and 100.26 ± 0.68 for the two drugs, respectively. The proposed methods were successfully applied to determine these drugs in their tablet formulations and the results compared favorably to that of reference methods. The proposed methods are recommended for quality control and routine analysis

  19. Halogen-bonding in a new family of tris(haloanilato)metallate(III) magnetic molecular building blocks.

    Science.gov (United States)

    Atzori, Matteo; Artizzu, Flavia; Sessini, Elisa; Marchiò, Luciano; Loche, Danilo; Serpe, Angela; Deplano, Paola; Concas, Giorgio; Pop, Flavia; Avarvari, Narcis; Mercuri, Maria Laura

    2014-05-21

    Here we report on new tris(haloanilato)metallate(III) complexes with general formula [A]3[M(X2An)3] (A = (n-Bu)4N(+), (Ph)4P(+); M = Cr(III), Fe(III); X2An = 3,6-dihalo derivatives of 2,5-dihydroxybenzoquinone (H4C6O4), chloranilate (Cl2An(2-)), bromanilate (Br2An(2-)) and iodanilate (I2An(2-))), obtained by a general synthetic strategy, and their full characterization. The crystal structures of these Fe(III) and Cr(III) haloanilate complexes consist of anions formed by homoleptic complexes formulated as [M(X2An)3](3-) and (Et)3NH(+), (n-Bu)4N(+), or (Ph4)P(+) cations. All complexes exhibit octahedral coordination geometry with metal ions surrounded by six oxygen atoms from three chelate ligands. These complexes are chiral according to the metal coordination of three bidentate ligands, and both Λ and Δ enantiomers are present in their crystal lattice. The packing of [(n-Bu)4N]3[Cr(I2An)3] (5a) shows that the complexes form supramolecular dimers that are held together by two symmetry related I···O interactions (3.092(8) Å), considerably shorter than the sum of iodine and oxygen van der Waals radii (3.50 Å). The I···O interaction can be regarded as a halogen bond (XB), where the iodine behaves as the XB donor and the oxygen atom as the XB acceptor. This is in agreement with the properties of the electrostatic potential for [Cr(I2An)3](3-) that predicts a negative charge accumulation on the peripheral oxygen atoms and a positive charge accumulation on the iodine. The magnetic behaviour of all complexes, except 5a, may be explained by considering a set of paramagnetic non-interacting Fe(III) or Cr(III) ions, taking into account the zero-field splitting effect. The presence of strong XB interactions in 5a are able, instead, to promote antiferromagnetic interactions among paramagnetic centers at low temperature, as shown by the fit with the Curie-Weiss law, in agreement with the formation of halogen-bonded supramolecular dimers. PMID:24626345