Electronic absorption and emission spectra and computational studies of some 2-aryl, 2-styryl, and 2-(4′-aryl)butadienyl quinazolin-4-ones

The relatively less popular group of quinazoline heterocyclic compounds is searched theoretically for compounds with promising classical and nonlinear optical properties, e.g. fluorescence and high (hyper)polarizabilities. Candidates for NLO materials are found among the general series of alpha-4-(3H)-quinazolonyl-omega-aryl polyenes 1, 2, 3 and their fluorescence spectra are registered experimentally. CIS/6-31G* calculations provide no reliable predictions of observed UV/Vis and fluorescence spectra. However, semiempirical CISD PM3 calculations predict fairly well the observed bathochromic effects arising from extension of polyene chains (CH=CH)(n), n = 0-2, and donor substitution in the aryl fragments. The observed fluorescence is assigned to planar quinonoid S1 emissive states, while ground SO state geometries of compounds with n = 0 are nonplanar, and with n > 0 are planar. We find high TDHF PM3 static polarizabilities for all studied molecules, as well as high hyperpolarizabilities beta SHG and gamma THG. (C) 2004 Elsevier B.V. All rights reserved.