THEORETICAL-STUDIES ON THE STRUCTURE AND ELECTRONIC-PROPERTIES OF 1,3,4-TRIAZOLIUM-2-AMIDINES

The structure and electronic properties of a series of substituted 1,3 ,4-triazolo-2-(N-phenyl) amidines have been explored in terms of their dipole moments and first hyperpolarisabilities using a semi-empirical sum-over-states and a time-dependent coupled Hartree-Fock approach. T he presence of an electron-attracting group in the phenyl ring results in a sharp increase in the dipole moment which increases substantiall y to 20 D with the introduction of an electron-donating 4-(N,N-dimethy lamino)phenyl group into the 5-position of the heterocyclic ring. Rela ted triazoles containing electron attractors show unexpectedly large h yperpolarisabilities which exceed those found for many conventional do nar-acceptor systems.