Photophysical and computational studies on optoelectronically active thiophene substituted 1,3,4-oxadiazole derivatives

摘要

In the present work, the photophysical properties of three novel optoelectronically active thiophene substituted 1,3,4-oxadiazole derivatives, namely 2-(4-(1H-inden-2-yl)pheny1)-5-(5-(1H-inden-2- yl) thiophen-2-yl)-1,3,4-oxadiazole [TIO], 2-(4-(thiophen-3-yl)pheny1)-5-(5-(thiophen-3-yl)thiophen-2-y1)-1,3,4-oxadiazole [TTO] and 2(4-(benzo [b] thiophen-2-yl)pheny1)-5-(5-(benzo[b]thiophen-2-ypthiophen-2-y1)-1,3,4-oxadiazole [TPO] have been investigated. The ground and excited state dipole moments (mu(e)) were determined experimentally by solvatochromic shift method using various solvatochromic correlations like Lippert's, Bakhshiev's, Kawski-Chamma-Viallet's and solvent polarity parameter (E-T(N)) equations. The ground state dipole moments (mu(g)) were also estimated from ab initio computations using Gaussian 09 W software. It is observed that, the excited state dipole moments are higher than the ground state dipole moments for all the probe molecules. This indicates that, the probe molecules are more polar in the excited state than in the ground state. The HOMO-LUMO energy gap computed using density functional theory (DFT) and from absorption threshold wavelengths are found to be in good agreement. The chemical hardness (eta) was determined for all the probes from HOMO-LUMO energies and results suggest the soft nature of the molecules. Further, the reactive centers like electrophilic site and nucleophilic site were identified with the help of molecular electrostatic potential (MESP) 3D plots using DFT computational analysis. Our preliminary investigations suggest that, the derivatives of 1,3,4-oxadiazoles namely TIO, TTO and TPO could play an important role in photonic, sensor and optoelectronic devices in future.