Synthesis and evaluation of changes induced by solvent and substituent in electronic absorption spectra of some azo disperse dyes (original) (raw)
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Changes induced by solvent polarity in electronic absorption spectra of some azo disperse dyes
Journal of Molecular Liquids, 2010
The electronic absorption spectra of some azo disperse dyes in various solvents of different polarities have been studied at room temperature. The solvent effects on the wavenumbers of the absorption band maxima (ṽ max) were discussed using the following solvent parameters, refractive index, n, dielectric constant, ε and empirical Kamlet-Taft solvent parameters, π* (dipolarity/polarizability), α (hydrogen bond donating capacity) and β (hydrogen bond accepting ability). The solute-solvent interactions were determined on the basis of multilinear solvation energy relationships concept. The fitting coefficients obtained from this analysis allowed us to estimate the contribution of each type of interactions to the total spectral shifts in solution. The established dependences between ṽ max and the solvent parameters emphasize that the visible band of the studied molecules is affected by both non-specific and specific solute-solvent interactions.
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).
Fibers and Polymers, 2019
The effect of solvent atmosphere on the electronic absorption properties of 2-aminothiazole based monoazo disperse dyes are studied. The synthesized monoazo dyes with different substituents on the para position of phenyl ring led to changes in the absorption properties of these dyes. Further, the positive solvatochromism data was evaluated to get the excited and ground state dipole moment ratio of the dyes. The Kamlet-Taft and Catalan polarity scales were employed wherein the solvent basicity and dipolarity is responsible for the bathochromic shift with increase in solvent polarity. The free amino group in the dyes made it responsive towards protonation by trifluoroacetic acid. The acidochromic behavior of the dyes was studied and D1, D3, and D4 exhibited major color change to longer wavelength with emergence of a new red shifted absorption band at 556 nm, 580 nm, and 540 nm, respectively, in their absorption spectra. Thus with help of simple UV-Vis absorption studies, we have studied the intermolecular interactions of the 2-aminothiazole based mono azo acidochromic probe.
Journal of Photochemistry and Photobiology. A, Chemistry
The solvatochromism and other spectroscopic and photophysical characteristics of four azo disperse dyes, derived from 2-amino-5-nitrothiazole, were evaluated and interpreted with the aid of experimental data and quantum mechanical calculations. For the non-substituted compound two conformers, E and Z, were proposed for the isolated molecules, being the second one considerably less stable. The optimization of these structures in combination with a SCRF methodology (IEFPCM, simulating the molecules in a continuum dielectric with characteristics of methanol), suggests that the Z form is not stable in solution. This same behaviour is expected for the substituted compounds, which is corroborated by experimental data presented in previous investigations [A.E.H. Machado, L.M. Rodrigues, S. Gupta, A.M.F. Oliveira-Campos, A.M.S. Silva, J. Mol. Struct. 738 (2005) 239-245].
In this study, absorption spectra of sixteen azo dyes have been recorded in various solvents. These azo dyes have substituents such as OH, SO3H, Cl, I, NO2, C2H5 and OCH3 in different positions of phenyl ring. There is a shift in λmax whose amount is dependent upon the type and position of substituent on the ring. The effects of substituent on the absorption spectra of azo dyes are interpreted by correlation of absorption maximum wavelengths (nm) with the hammett substituent parameters. Charge transfer transitions are observed in inverse direction for azo dyes with electron acceptor substituent compared to azo dyes with electron donor. Keyword: Absorption spectra, azo dye, electronic charge transfer hammett substituent constant, non-linear optic,
Journal of Molecular Liquids, 2010
Absorption spectra of three disperse azo dyes with various molecular sizes and alkyl tails have been recorded in isotropic and anisotropic solvents in the range between from 200 to 700 nm. The photo-physical behavior of a dissolved dye depends on the nature of its environment, i.e. the intensity, shape, and maximum absorption wavelength of the absorption band depends strongly on the solute-solvent interactions and solvent nature. The solvatochromic behaviors of disperse azo dyes and solute-solvent interactions can be analyzed by means of the linear solvation energy relationship concept proposed by Kamlet and Taft. Bathochromic shift of absorption maxima of these dyes, λ max , occurs in solvents with highest proton acceptor ability and dipolarity/polarizability.
Journal of Molecular Liquids, 2009
A series of monoazo disperse dyes based on N-phenyl-2, 2′-iminodiethanol were synthesized using p-substituted anilines as diazo components. The prepared dyes were characterized by UV-vis, FT-IR and 1 H NMR spectroscopic techniques. The effect of varying pH and the evaluation of solvatochromic properties of synthesized dyes with donor-acceptor p-substituted groups are described. The absorption maxima of these dyes changed very significantly by the introduction of various substituents on the para-position of benzene ring.
UV-spectral changes for some azo compounds in the presence of different solvents
Journal of Molecular Liquids, 2011
The electronic absorption spectra of four azo dyes with different substituents (such as Cl, I, OH) are determined at room temperature in twenty-one solvents with different polarities. The electronic transitions of azo dyes are interpreted. Linear solvation energy relationships have been investigated for solvatochromic behaviors and solute-solvent interactions of azo dyes. Linear solvation energy relationships were performed by multiple linear regression analysis using dielectric function, refractive index function and Kamlet-Taft parameters. We have observed that the hydrogen bonding acceptor ability and the induction-dispersive forces of solvent molecules have caused the bathochromic shift in absorption maxima of azo dyes.
2010
Solvent polarity effect on the photophysical properties of two newly synthesized aminostyryl-thiazoloquinoxaline dyes, one with a flexible diphenylamino group, namely, N,N-diphenyl-4-[2-(thiazolo[4,5-b]quinoxalin-2-yl)vinyl]aniline (TQ1), and the other with a rigid julolidinylamino group, namely, (9-[2-(thiazolo[4,5b]quinoxalin-2-yl)vinyl]julolidine) (TQ2), have been investigated in different aprotic solvents and solvent mixtures. From the polarity dependent changes in the absorption and fluorescence spectral properties, it is indicated that the fluorescent states of the dyes are of intramolecular charge transfer (ICT) character. For both the dyes, the photophysical properties like fluorescence quantum yields (Φ f ), fluorescence lifetimes (τ f ), radiative rate constants (k f ) Φ f /τ f ), and nonradiative rate constants (k nr ) 1/τ f -Φ f /τ f ) show clearly contrasting solvent polarity effects in the lower and in the higher solvent polarity region, causing an interesting reversal in the properties below and above an intermediate solvent polarity. It is inferred that the domination of the cis-trans isomerization in the lower solvent polarity region and that of the twisted intramolecular charge transfer (TICT) state formation in the higher solvent polarity region are responsible for the observed contrasting solvent polarity effects on the photophysical properties of the two dyes. As both isomerization and TICT state formation causes an enhancement in the nonradiative decay rate of the excited dyes and both the processes become less significant at the intermediate solvent polarity region, the two dyes show their largest Φ f and τ f values at intermediate solvent polarities. Suitable mechanistic schemes have been proposed and qualitative potential energy diagrams have been presented to explain the observed results with the changes in the polarity of the solvents used.