الفهرس 
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Abstract
Solvation-dependent photophysical properties of two push–pull thiophene-based compounds with donor–π–acceptor (D–π–A) structures were investigated using absorption, fluorescence emission and time re-solved spectroscopy, and supported by different solvation models. In-tramolecular charge transfer characteristics of these structurally similar 2-fluoro-4-(5-(4-methoxyphenyl) thiophen-2-yl) benzonitrile (MOT) and 4-(5-(4-(dimethylamino) phenyl) thiophen-2-yl)-2-fluorobenzonitrile (DMAT) were investigated.
Significant enhancement of intramolecular charge transfer strength has been observed through molecular structure modification of the electron donating group from methoxy to dimethylamine group. Ground state absorption spectra show a small red shift of about 10 nm and 18 nm while the fluorescence emission spectra show a large red shift of about 66 nm and 162 nm on changing from the nonpolar cyclo-hexane to the aprotic polar DMSO for MOT and DMAT, respectively. Dipole moment change from the ground state to the charge transfer excited state is calculated to be 6.6 D in MOT and 9.0 D in DMAT.
The fluorescence quantum yield, fluorescence lifetime and the derived radiative and non-radiative rate constants were found to be bet-ter correlated to the emission energy rather than any of the solvent properties. Three multi-parametric relationships were used in the in-terpretation of the specific versus non-specific solute-solvent interac-tions, namely, Kamlet-Taft, Catalán and Laurence et al models.
The findings of these approaches are used to extract useful in-formation about different aspects of solvent effect on the photophysical properties of the two compounds. Kamlet–Taft solvatochromic model indicates that non-specific interactions are dominant in controlling the photophysical properties. Catalán’s solvent dipolarity/polarizability pa-rameter is found to play significant role in solvatochromic behavior which is also designated by Laurence model.