SYNTHESIS AND PROPERTIES OF A NEW KIND OF ONE-DIMENSIONAL CONDUCTORS .2. EXTENDED HUCKEL CALCULATIONS ON THE ENERGY-BAND STRUCTURE

The co-ordination polymer of tetrazaporphin (TAP) with a transition metal, say Fe11, in its center and acetylide anion, C22?, as an axial bidentate bridging ligand is taken as a model sub-stance for the new type of one-dimensional conductors introduced in the preceding communication of this series. Although the monomer shows symmetry, this is reduced to C4V for arbitrary K2-values of the Bloch functions of the first Brillouin zone. From the irreducible representations a1, a2, b1, b2, and e only a1 and e have contributions from all components, namely TAP2?, Fe2? and C22?, so that for these races broad energy bands can be expected. The a%, b, and b2 MOs of the TAP-Fe11 subunits are separated fairly well and have no counterparts in the C22? bridges so that very narrow bands should arise. This is confirmed by an EH calculation. Unexpectedly the ai bonds which have contributions from the a-MOs of C22? are broader than the e-bands which contain the two crossed tt-MO systems of Co2?. The quantitative results of the nearly self-consistent iterative EH calculation indicate overlap of the energy bands near the Fermi level and fulfill thus one necessary condition for metal-like electrical conductivity. © 1979, Walter de Gruyter. All rights reserved.