A comprehensive spectroscopic and computational investigation of intramolecular proton transfer in the excited states of 2-(2′-hydroxyphenyl) benzoxazole and its derivatives

The excited-state intramolecular proton transfer (ESIPT) fluorescence of the 2-(2' hydroxyphenyl) benzoxazole (HBO) and its derivatives with NO2 as electron acceptor and NH2 as electron donor at the 4 and 5 position of benzoxazole ring was studied by spectroscopic and computational methods. The changes in the electronic transition, energy levels, and orbital diagrams of the HBO derivatives were investigated using the DFT computations and they were correlated with the experimental spectral emission. The benzoxazole derivatives are fluorescent under UV-light in solution. Photophysical properties of the compounds were also studied in solvents of different polarities. Experimental absorption and emission wavelengths are in agreement with those computed with a deviation ranging between 0 and 50%. The computational methods have been useful for molecular understanding of the transitions responsible for the fluorescent spectra. (C) 2013 Elsevier B.V. All rights reserved.