Heterocyclic dyes displaying excited-state intramolecular proton-transfer reactions (ESIPT): computational study of the substitution effect on the electronic absorption spectra of 2-(2′-hydroxyphenyl)-1,3-benzoxazole derivatives†

Abstract

Semi-empirical molecular-orbital methods were used to simulate the electronic absorption spectra of a series of 2-(2′-hydroxyphenyl)-1,3-benzoxazole derivatives, namely AM1 and MNDO-PM3 for geometry optimization and INDO/S-CI and HAM/3 for spectroscopic features. Wavelengths of maximum absorption that agree better with experimental data were found when INDO/S-CI was applied to PM3-generated inputs. Chemical substitution red-shifted the absorption spectrum of all the model compounds, a feature discussed based on the calculated energy levels of frontier orbitals and charge redistribution upon electronic excitation.