Solvatochromism and azo–hydrazo tautomerism of novel arylazo pyridone dyes: Experimental and quantum chemical study (original) (raw)
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Acta Physica Polonica A, 2016
The optimized geometrical structures, infrared spectra, molecular electrostatic potential, natural bond orbital and nonlinear optical properties of 5-phenylazo-6-hydroxy-4-phenyl-3-cyano-2-pyridoine (1) and 5-(4-bromophenylazo)-6-hydroxy-4-phenyl-3-cyano-2-pyridoine (2) dyes with a detailed study on the azo-hydrazone tautomerism in the ground state have been investigated by density functional theory using B3LYP functional with 6-31G(d,p) basis set. Vibrational modes are assigned with the help of vibrational energy distribution analysis program. Highest occupied molecular orbital and lowest unoccupied molecular orbital energies of the (1) and (2) compounds with azo and hydrazone forms were calculated with the same method and basis set. Molecular parameters like global hardness (η), global softness (σ) and electronegativity (χ) were calculated with the results obtained from the highest occupied and lowest unoccupied molecular orbital energies. Nonlinear optical parameters (mean polarizability (α), the anisotropy of the polarizability (∆α) and the mean first-order hyperpolarizability (β)) of the title compounds were investigated theoretically. The atomic charges, electronic exchange interaction, and charge delocalization of the molecules have been studied by natural bond orbital analysis.
Effect of Cooperative Hydrogen Bonding in Azo−Hydrazone Tautomerism of Azo Dyes
The Journal of Physical Chemistry A, 2007
Azo-hydrazone tautomerism in azo dyes has been modeled by using density functional theory (DFT) at the B3LYP/6-31+G(d,p) level of theory. The most stable tautomer was determined both for model compounds and for azo dyes Acid Orange 7 and Solvent Yellow 14. The effects of the sulfonate group substitution and the replacement of the phenyl group with naphthyl on the tautomer stability and on the behavior in solvent have been discussed. Intramolecular hydrogen bond energies have been estimated for the azo and hydrazone tautomers to derive a relationship between the tautomer stability and the hydrogen bond strength. The transition structures for proton transfer displayed resonance assisted strong hydrogen bonding properties within the framework of the electrostatic-coValent hydrogen bond model (ECHBM). Evolution of the intramolecular hydrogen bond with changing structural and environmental factors during the tautomeric conversion process has been studied extensively by means of the atoms-in-molecules (AIM) analysis of the electron density. The bulk solvent effect was examined using the self-consistent reaction field model. Special solute-solvent interactions were further investigated by means of quantum mechanical calculations after defining the firstsolvation shell by molecular dynamics simulations. The effect of cooperative hydrogen bonding with solvent molecules on the tautomer stability has been discussed.
Journal of Molecular Structure, 2013
Please cite this article as: A. Ünal, B. Eren, E. Eren, Investigation of the azo-hydrazone tautomeric equilibrium in an azo dye involving the naphthalene moiety by UV-vis spectroscopy and DFT and quantum chemistry, Journal of Molecular Structure (2013), doi: http://dx.ABSTRACT Photophysical properties of the azo-hydrazone tautomerism of Eriochrome Blue Black B (1-(1-hydroxy-2-naphthylazo)-2-naphthol-4-sulphonic acid) in DMF, MeCN and water were investigated using UV-visible spectroscopy and quantum chemical calculations. The optimized molecular structure parameters, relative energies, mole fractions, electronic absorption spectra and HOMO-LUMO energies for possible stable tautomeric forms of EBB were theoretically calculated by using hybrid density functional theory, (B3LYP) methods with 6-31G(d) basis set level and polarizable continuum model (PCM) for solvation effect.
A study on optimum transition state and tautomeric structures of a bis-heterocyclic monoazo dye
Indian Journal of Physics, 2014
In this study, possible tautomeric forms and ground state conformers of a bis-heterocyclic monoazo dye, 4-[ethyl 4 0-methyl-5 0-(phenylcarbamoyl)thiophene-3 0-carboxylate-2 0-ylazo]-3-methyl-1H-pyrazolin-5-one, have been calculated using density functional theory methods with 6-31G (d) basis set. 1 H and 13 C chemical shifts of tautomeric forms have been calculated. Calculated vibrational frequencies and chemical shifts have been compared with corresponding experimental data. Using time-dependent Hartree-Fock method, electronic absorption spectrum of title compound has been calculated and compared with experimental maximum wavelength data. Quantum Synchronous Transit2 approaches have been used for finding the optimum transition state and tautomeric forms of studied molecule. Calculations have shown that the most probable preferential form of this molecule in ground state is hydrazo-keto form. The calculations of frontier molecular orbitals and first order hyperpolarizability have also confirmed this stability.
Journal of Molecular Liquids, 2014
Five novel azo-hydrazone tautomeric dyes 3a-e were synthesized in two steps using Knoevenagel condensation and azo coupling reaction. The structures of the new compounds were confirmed by UV-vis, IR and NMR spectroscopies. Spectral data indicated that these dyes exist predominantly in the hydrazone tautomeric form in solutions. In addition, the absorption ability of the dyes showed that the solvent effect on UV-vis absorption spectra is complex and effectively depends on the nature of the substituent on the diazo component. The effects of acidic and basic media on the visible absorption spectra of the dyes were also examined. The antibacterial and antioxidant activities of the dyes were characterized using the agar well diffusion and ferric reducing antioxidant power (FRAP) methods, respectively. The synthesized dyes exhibited both antioxidant and antibacterial activities.
Spectrochimica Acta Part A Molecular Spectroscopy
The spectral behaviour of six a-hydroxy azo compounds has been investigated in solution. The bands appearing in the u.v. and visible regions are assigned to possible electronic transitions. Azo compounds containing pyrazoione and acetyl or ester moieties are found to exist mainly in the hydrazo form in solution, while those containing the naphthol moiety exist in the azo-hydrazone tautomeric equilibrium. The solvatochromic behaviour of the compounds is investigated by studying their spectra in organic solvents of different polarities. The acidity constants are determined from the spectra of the compounds in aqueous ethanolic solutions of varying pH values.
Journal of The Serbian Chemical Society, 2010
A series of some new pyridone arylazo dyes was synthesized from the corresponding diazonium salts and 3-cyano-4,6-diphenyl-2-pyridone using the classical reaction for the synthesis of the azo compounds. The structures of these dyes were confirmed by UV-Vis, FT-IR and 1 H-NMR spectroscopic techniques. The solvatochromism of the dyes was evaluated with respect to visible absorption properties in various solvents. The effects of solvent dipolarity/polarizability and solvent/solute hydrogen bonding interactions were analyzed by means of the linear solvation energy relationship concept proposed by Kamlet and Taft. The 2-pyridone/2-hydroxypiridine tautomeric equilibration was found to depend on the substituents as well as on the solvents.
A series of new 3-arylazo-6-methyl-2,8,9-triphenyl-8H-imidazo[1,2-b]pyrazolo[4,3-d]pyridazines was prepared via reaction of hydrazonoyl halides with 3-hydrazonoacetyl-4-cyano-1,5-diphenylpyrazole. The structures of the compounds prepared were confirmed by spectral and elemental analyses. The solvatochromic and substituent effects on the absorption spectra of these azo dyes were interpreted by correlation of absorption frequencies with Kamlet–Taft and Hammett equations, respectively.
Solvent Effects on the Electronic Spectra of Some Heterocyclic Azo Dyes
Bulletin of the Korean Chemical Society, 2014
The influence of solvent polarity on the absorption spectra of some synthesized azo dye with heterocyclic moieties and -naphthol (1-3) have been investigated using a UV-Visible spectrophotometer. The spectral characteristics of the azo dyes (1-3) in different solvents at room temperature were analyzed. The solvatochromic empirical variables like * , , and have been used to discuss the solvatochromic behaviour of the dyes and to evaluate their contributions to the solute-solvent interactions. A multi-parameter regression model for quantitative assessment of the solute/solvent interaction and the absorption has been used to explain the solvent effect on azo dyes (1-3).