Computational study of the excited states of 2,5-bis(benzoxazol-2′-yl)hydroquinone and its monomethoxy derivative

Abstract

The geometry of the title compounds in the ground state and in the first excited singlet state have been investigated using AM1 semi-empirical molecular orbital calculations. The data obtained have been employed in a comparative study of the HAM/3 and the INDO/S-CI computational methods for electronic spectra simulation. AM1 results show that the most stable forms of the studied structures are H-bonded structures—enol and keto tautomers for the ground state and first excited singlet state, respectively. Concerning spectroscopic results, INDO/S-CI yields numerical values of excitation energy that better agree with experimental data, while HAM/3 better describes the distribution and relative intensities of the absorption/emission bands.