BONDING IN 1,2,3-TRIAZOLES .7. EFFECTS OF N-SUBSTITUTION - AB-INITIO CALCULATIONS ON MODEL SYSTEMS

Ab initio LCAO-MO-SCF calculations have been performed for the triazol e anion, 1H- and 2H-triazole, and the 1,2- and 1,3-triazolium ions (do uble-zeta basis set, polarization functions). The geometry of the tria zole skeleton was determined by energy minimization of the triazole an ion with a double-zeta basis set of lower accuracy. The resulting geom etry is partly verified via geometrical correlations obtained from the crystal structures of several 1,2,3-triazoles. The deformation densit ies for the different types of substitution show a high degree of addi tivity that is also present in several parameters obtained by Mulliken population analyses. Similar additivity rules also apply to several o rbital energies, including the energies of the highest occupied orbita l (HOMO) and the lowest unoccupied orbital (LUMO).