Ab initio calculations on 2-imidazolyl-2-thiazolyl azo compounds - an investigation of potential near-infrared absorbing structures

The two lowest singlet excitation energies of 26 2-imidazolyl-2-thiazolylaz o compounds have been investigated by ab initio methods within the second-o rder polarization propagator approximation (SOPPA). Various combinations of 4- and 5-substituents at both the imidazole and thiazole units have been s tudied for obtaining pi --> pi* excitation energies corresponding to an abs orption maximum in the red or infrared regions. In many cases, pi --> pi ex citation energies below 2 eV (corresponding to wavelengths longer than 600 run) are found for molecules that possibly may be synthesized. For the mole cules included in this study, the longest wavelength was calculated to be 1 049 nm. (C) 2001 Elsevier Science B.V. All rights reserved.