Abstract
Work on modelling compounds possessing die tetraaza[14]annulene (TAA) fragment is described. Modelling studies have been conducted to investigate both structural and electronic properties, of both single molecules and extended arrays of these compounds. The structural aspects have been investigated using molecular mechanics and crystallographic database investigations. Molecules based on the tetraaza[14] annulene structure have been found to adopt one of four conformations. The geometries of these conformations are planar, saddle-shaped, slightly twisted, and dome-shaped. The complexed metal centre and the arrangement of substituents on the periphery of the ligand, have been found to determine which conformation a molecule adopts. In order to model the compounds, three new atom types have been created for the Universal Force Field. The electronic aspects have been investigated using Hartree Fock based calculations for single molecules and Extended Huckel based calculations for extended systems. The electronics of die single molecules have shown there to be a linear trend in the LUMO energies, although die HOMO energies vary very little. The reason for this trend in the LUMOs is unknown, but appears not to be related to any obvious structural feature.