Experimental and theoretical spectroscopic studies of ortho derivatives of methyl p-dimethylaminobenzoate

Abstract

Steady-state spectroscopic studies of two ortho (–OCH 3 and –OH) derivatives of methyl p-dimethylaminobenzoate have been performed. The absorption spectra of molecules under study are analyzed taking into consideration results of quantum chemical semiempirical calculations. The fluorescence spectra of these molecules possess in polar solvents two bands, i.e., the locally excited and intramolecular charge transfer (ICT) fluorescence band. Their intensity ratio as well as the fluorescence/phosphorescence intensity ratio determined at 77 K depends on the solvent polarity. Theoretical studies of the TICT phenomenon have been made in order to explain the dual emission of molecules under study. Calculated electric dipole moments of these molecules in the ground, S 0, and excited, S 1(LE) and S 1(ICT) states, have been compared with experimentally determined data. Theoretically determined transition energies, Δ E i , oscillator strengths, f i , and electric dipole moments μ S 0 , μ S 1 ( LE ) and μ S 1 ( ICT ) of the planar donor–acceptor (D/A) conformer agree with experimental data. According to Marcus theory inner- and outer-solvatation sphere reorganization energies ( λ out, λ in) are calculated using the determined spectroscopic properties of molecules under study.