Spectral investigations of preferential solvation and solute-solvent interactions of 1,4-dimethylamino anthraquinone in CH2Cl2/C2H5OH mixtures

Solvatochromism, Preferential Solvation and Multiparametric Approach to the Spectral Shift of Methyl Orange in Aqueous Cosolvent Mixtures

In this study, the solvatochromic behavior of Methyl orange was studied visible spectrophotometrically in seven aqueous binary systems from water with methanol, ethanol, propanol, DMF, DMSO, acetone and dioxane solvents. The spectral data was interpreted in terms of solute-solvent and solvent-solvent interactions. The deviation from linearity in the plots of νmax versus x2 due to preferential solvation of the Methyl orange by one component of the mixed solvent and due to solvent microheterogeneity. The preferential solvation parameters local mole fraction X2L, solvation index δs2 and exchange constant K12 were evaluated. The preference of solute to be solvated by one of the solvating species relative to others was explained. All values of K12 were less than unity that indicates the preferential solvation of Methyl orange by water, except in case the water-propanol mixture where K12 was higher than unity. The preferential solvation index δs2 values were calculated and interpreted for each binary mixture. The magnitude of preferential solvation index was highest in water-DMSO mixtures than in the all other solvent mixtures. The energy of electronic transition in maximum absorption (ET) was calculated in each binary mixture. The extent and importance of each solute-solvent interactions to ET were analyzed by the linear solvation energy relationships using the Kamlet-Taft strategy.

The Preferential Solvation of Methyl Red in Various Binary Aqueous Solutions: Solvatochromism, Preferential Solvation Parameters, Microheterogeneity of Solvents and Polarity Scale

The solvatochromic characteristics of methyl red were examined in several aqueous solutions from pure water, with methanol, ethanol, propanol, acetonitrile, and dioxane. In order to explain the preferred solvation of the probe azo dye in the binary mixed solvents, the solvent exchange model of Bosch and Roses was used to evaluate the association between the empirical solvent polarity scale (ET) values of MR and solvent composition. Non-linear solvatochromism of methyl red was noted in all aqueous mixtures containing methanol, ethanol, propanol, acetonitrile, and dioxane. In addition to calculating the local mole fraction of each solvent composition in the cybotactic area of the probe, the impact of the solvating shell composition on the preferential solvation of the solute dye was examined in terms of both solvent-solvent and solute-solvent interactions. The local mole fraction of each solvent composition in the cybotactic region of the probe was also calculated. The results indicated that the MR solvation shell was thoroughly saturated with the solvent complex S12 in the following order: dioxane > ethanol > methanol > acetonitrile > propanol. Data from the binary systems were analyzed with KAT parameters using a multi-model; in aqueous methanol and ethanol solutions, the hydrogen acidity was more responsible for the spectral shift, whereas in aqueous acetonitrile and dioxane solutions, the basicity has a greater influence.

Reinvestigation of the photophysics of 3-aminobenzoic acid in neat and mixed binary solvents

The present study elucidates the reinvestigation of the photophysical behavior of 3-aminobenzoic acid (3ABA) in solvents of different polarities using the steady-state spectroscopic techniques. Kamlet-Taft and Catalan solvatochromic models have been used to analyze the solvatochromic changes in neat solvents. The hydrogen bond donating ability of the solvent was found to be the main parameter affecting the spectral behavior of 3ABA. The solvatochromic characteristics of 3ABA have also been examined in binary solvent mixtures viz. acetonitrile (ACN)-methanol (MeOH) and benzene (BEN)-MeOH using the concept of preferential solvation. The preferential solvation of 3ABA shows unusual behavior for BEN-MeOH binary mixture and described unnoticed sigmoidal behavior in the ground state and synergistic impact in the excited state. Besides, the 3ABA was studied theoretically by quantum chemical calculations using (HF) Hartree-Fock and (DFT/B3LYP) density functional theories and its electronic absorption bands have been assigned by time-dependent density functional theory (TD-DFT). The effect of solvents on 3ABA was considered using a IEF-PCM-TDDFT (integral equation formalism of the polarizable continuum model- TDDFT) method. Thus, the theoretical results were found to be closer to the experimental results.

Ground and excited state preferential solvation behaviour of 1,4-dihydroxy-3-methylanthracene-9,10-dione in DMF+CCl4 binary system

Preferential solvation of 1,4-dihydroxy-3-methylanthracene-9,10-dione (DHMAD) has been investigated using optical absorption and fluorescence emission techniques. Optical absorption spectra of DHMAD in different solvents show the intra molecular charge transfer band in the region 400-550 nm. The preferential solvation parameter shows that in dimethyl formamide (DMF)+carbon tetrachloride (CCl(4)) mixture, the DHMAD is preferentially solvated by DMF in the ground state and in the excited state DHMAD is preferentially solvated by CCl(4) in DMF rich region and by DMF in CCl(4) rich region.

Investigations of preferential solvation on 1,4-dimethoxy-3-methyl anthracene-9,10-dione

Preferential solvation of 1,4-dimethoxy-3-methyl anthracene-9,10-dione (DMMAD) has been investigated using optical absorption technique. The preferential solvation parameters show that the DMMAD is preferentially solvated by acetone in acetone (AC)+propan-2-ol (PROH), AC+CH2Cl2 and AC+CCl4 mixtures. DMMAD prefers PROH in PROH+CCl4 mixture. In the case of benzene+CCl4 mixture DMMAD is preferentially solvated by benzene in benzene rich region and by CCl4 in CCl4 rich region. The results have been discussed in terms of hydrogen bonding, dipole-dipole and induced dipole-dipole interactions between DMMAD and solvent molecules.

Solvatochromic behavior on the absorption and fluorescence spectra of Rose Bengal dye in various solvents

The absorption and fluorescence spectra of Rose Bengal dye were studied in various solvents. It was found that solvent effects on the absorption wavelength are consistent with the solvatochromic model of Kamlet, Abboud and Taft. The solvent polarizability value pi* was found to have a linear relationship with the absorption wavelength of the dye in various solvents. Additionally, the normalized transition energy value (E(T)(N)) showed some scattering when plotted versus Deltanu(af). Density functional calculations were used to assign the absorption in the region 540-570 nm to a pi-pi* transition between the HOMO and LUMO of the anion. Experimental ground state and excited state dipole moments were calculated by using the solvatochromatic shifts of absorption and fluorescence spectra as a function of the dielectric constant (epsilon) and refractive index (n). The dipole moment for Rose Bengal was found to be 1.72 Debye in the ground state, whereas this value was 2.33 Debye in the excited state.

Merocyanine solvatochromic dyes in the study of synergistic effects in mixtures of chloroform with hydrogen-bond accepting solvents

The molar transition energy (E(T)) polarity values for the solvatochromic probes 2,6-diphenyl-4-(2,4,6-triphenylpyridinium)phenolate (1), 4[(1-methyl-4-(1H)-pyridinylidene)-ethylidene]-2,5-cyclohexadien-1-one (2), and 4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide (3) were collected in binary mixtures comprising chloroform and a hydrogen-bond accepting (HBA) solvent [dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), acetone or acetonitrile], aiming to investigate the ability of the chlorinated component to act as hydrogen-bond donating (HBD) solvent. Plots of E(T) as a function of X(2), the mole fraction of chloroform, were obtained and the data were analysed to investigate the preferential solvation (PS) of each probe in terms of both solute-solvent and solvent-solvent interactions. For dyes 1 and 2 a strong synergistic behavior was observed for all mixtures studied, indicating that the dyes are preferentially solvated by complexes formed through hydrogen bonding between chloroform and the HBA component in the mixtures. A study of 1 in deuterated chloroform with an HBA component (DMF and DMA) demonstrated that while almost no differences occur with the DMF mixtures, the presence of deuterated chloroform in its mixtures with DMA increases the synergistic effect, suggesting that it interacts more strongly with DMA, making its mixtures more polar. These data were successfully fitted to a model based on solvent-exchange equilibria. The features of the mixtures with dye 3 revealed a very different profile in comparison with the other two dyes, which suggests that in mixtures containing chloroform, the microenvironment of the dye seems to be important in determining the contribution of the structure resonances responsible for the stability of the dye.