ELECTRONIC-STRUCTURE OF TETRACOORDINATE TRANSITION-METAL COMPLEXES .5. COMPARATIVE THEORETICAL ABINITIO HARTREE-FOCK-SLATER AND ULTRAVIOLET-PHOTOELECTRON SPECTROSCOPIC STUDIES OF BUILDING-BLOCKS FOR LOW-DIMENSIONAL CONDUCTORS - DIBENZO[B,I][1,4,8,11]TETRAAZACYCLOTETRADECINE COMPLEXES OF NICKEL(II) AND PALLADIUM(II)

The electronic structure of the Ni and Pd complexes of the title ligand have been studied by an integrated experimental He I/He II photoelectron spectroscopic as well as theoretical ab initio pseudopotential and first-principles local exchange DV-X-alpha approach. Theoretical calculations have provided a complete assignment of photoelectron spectra as well as useful information on the peculiarities of the valence electronic system that, in turn, is of relevance in understanding the properties of low-dimensional, partially oxidized, [M(TAA)P+]n systems. Furthermore, similarities and differences between the present complexes and partially oxidized metallophthalocyanines are discussed in terms of the nature of the HOMO and of twisting motion effects upon the valence bandwidths. The present results argue that the charge transport in tetraazaannulene molecular conductors occurs via bands that are predominantly ligand pi-electron in character, and that twisting motions (librations) scarcely affect the resistivity.