Synthesis, solvatochromism, electronic structure and nonlinear optic properties of quinolin-8-yl 2-hydroxybenzoate

Abstract

Quinolin-8-yl 2-hydroxybenzoate (QHB) was synthesized and its physical and electronic proper-ties were investigated both experimentally and theoretically. The electronic structure and spectral behav-ior were determined by using UV-vis absorption and fluorescence spectra in 11 different polarity solvent media. The absorption band observed at 306-308 nm is attributed to π-π* and n-π* electronic transitions due to its geometric structure in the solution phase. Solvatochromism of QHB was investigated by using Kamlet-Taft and Catalan methods based on the linear solvation energy relationships (LSER). The Kam-let-Taft solvatochromic model indicates that spectral shifts of absorption and fluorescence spectra are ef-fectively controlled by dispersion-polarization forces which describe the non-specific interactions. The solvatochromic model of Catalan states that solute-solvent interaction is governed by solvent polarity in the absorption spectra and by solvent acidity in the fluorescence spectra. Non-specific interactions have a greater effect on fluorescence spectra compared to absorption spectra. Computational calculations were performed by the application of the B3LYP/6-311+(d,p) level of theory. Conformational analysis per-formed for QHB showed five staggered conformers on torsional potential energy surfaces. Accordingly, the most stable conformer was found to be the one involving intra-molecular hydrogen bonding. The ge-ometry of the other conformers indicated that the absence of hydrogen bonding gave rise to relatively higher energy. Frontier molecular orbitals (HOMO, LUMO) and non-linear optical (NLO) parameters were calculated by B3LYP/6-311+(d,p) level of theory. Theoretical UV spectra both in gas and solution phases were also investigated by TDDFT-CAM-B3LYP/6-311+(d,p) level of theory.