Synthesis and photophysical properties of a novel phthalimide derivative using solvatochromic shift method for the estimation of ground and singlet excited state dipole moments

A novel phthalimide derivative, 2-{4-[(1H-1,2,4-triazol-1-yl)methyl]phenyl}-1H–isoindole-1,3(2H)-dione (TMPID) containing an isoindole moiety was synthesized by the cyclisation of 2-({4-[(1H-1,2,4-triazol-1-yl)methyl]phenyl}carbamoyl)benzoic acid (TMPCB). The absorbance and fluorescence spectra of the derivative were recorded in fifteen different solvents to investigate their solvatochromic behaviour and dipole moments. Different solvent correlation methods, like the Bilot–Kawski, Lippert–Mataga, Bakhshiev, Kawski–Chamma–Viallet and Reichardt methods were employed to estimate the singlet excited and ground state dipole moments. Using multiple regression analysis, solute-solvent, specific and non-specific interactions were analyzed by means of Kamlet-Abboud-Taft and Catalan parameters. Computational studies were performed using time dependent density functional theory (TD-DFT) in order to calculate ground state dipole moment, atomic charges and frontier molecular orbital energies in solvent phase. Experimental and computational studies indicate that the singlet excited state dipole moment of TMPID is greater than the ground state dipole moment. The chemical stability of the derivative was determined by means of chemical hardness (η) using HOMO–LUMO energies. From TD-DFT computational analysis, reactive centres in the molecule were evaluated based on molecular electrostatic potential (MESP) 3D plots.