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The substituent and solvent effects on solvatochromism in 3-[(4-substituted) phenylamino]isobenzofuran-1(3H)-ones were studied using experimental and theoretical methodologies. The effect of specific and non-specific solvent–solute interactions on the shifts of UV–Vis absorption maxima were evaluated using the Kamlet–Taft and Catalán solvent parameter sets. The experimental results were studied by density functional theory (DT) and time-dependent density functional theory (TD-DFT). The HOMO/LUMO energies (EHOMO/ELUMO) and energy gap (Egap) values, as well as the mechanism of electronic excitations and the changes in the electron density distribution in both ground and excited states of the investigated molecules were studied by calculation in the gas phase. The electronic excitations were calculated by the TD-DFT method in the solvent methanol. It was found that both substituents and solvents influence the degree of π-electron conjugation of the synthesized molecules and affect the intramolecular charge transfer character. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172013]

The substituent and solvent effect on intramolecular charge transfer (ICT) in 5-arylidene-3-methyl-2,4-thiazolidinediones (series 1) and 5-arylidene-3-phenyl-2,4-thiazolidinediones (series 2) was studied by using experimental and theoretical methodology. The effect of specific and non-specific solvent–solute interactions on the UV–vis absorption maxima shifts was evaluated by using the Kamlet-Taft and Catalán solvent parameter sets. Linear free energy relationships (LFERs) have been applied to the UV–vis and 13C NMR data by using SSP (single substituent parameter) and DSP (dual substituent parameters). Comparative LFER analysis of 10 styrenic series was performed in order to distinguish contribution of structural and electronic substituent effect on extent of π-polarization in a side chain (vinyl) group. Furthermore, the experimental findings were interpreted with the aid of ab initio MP2 and time-dependent density functional (TD-DFT) methods. TD-DFT calculations are performed to quantify the efficiency of intramolecular charge transfer (ICT) allowing us to define the charge-transfer distance (D CT), amount of transferred charge (Q CT), and difference of dipole moments between the ground and excited states (μ CT). It was found that both substituents and solvents influence electron density shift, i.e. extent of conjugation, and affect intramolecular charge transfer character in the course of excitation. [ABSTRACT FROM AUTHOR]