Solvatochromism of isatin based Schiff bases: An LSER and LFER study

Abstract

The derivatives of isatin have already been reported to show a variety of biological activities. However, there has been no report on solvatochromic effect of isatin derivatives so far, and that could be of interest to study and relate to their electronic structure, as a part of the characterisation of these compounds. Linear solvation energy relationships (LSER) were used to analyze solvent influence on the UV absorption maxima shifts of investigated isatin derivatives, i.e. isatin based Schiff bases, by using Kamlet-Taft model. Linear free energy relationships (LFER) were applied to the substituent-induced NMR chemical shifts (SCS) using SSP (single substituent parameter). The obtained correlations together with theoretical calculations gave insight into the influence of the molecular conformation on the transmission of substituent effects, as well as on solute/solvent interactions. The molecular electrostatic potential (MEP) surface map was plotted over the optimized geometry of the molecules in order to visualize electron density distribution and explain origin of solvent/solute interactions.