Importance of the Phthalocyanine Ring Carbon π‐orbitals in the Electrical Conduction of Metal Phthalocyanine Polymers

Abstract

Abstract The electronic structures of metal phthalocyanine polymers PcMX and MPc were examined by performing tight‐binding band calculations on PcMX (MX = SiO, GeO, AlF, GaF, CrF) and MPc (M = Ni, Co, Fe) chains. The present band structure study suggests that the electrical conductivities of halogen‐doped PcMX and MPc chains are governed by their valence bands a composed of the HOMO a 1M of each Pc ring. It is the valence band a that becomes partially empty upon halogen‐doping. The Pc ring π‐orbital a 1M is made up of only the carbon p orbitals. By symmetry, none of the s, p and d orbitals of a metal atom M can mix into the a 1M orbital. Consequently, the width of the valence band a is solely determined by such factors as the inter‐ring separation and the inter‐ring rotation. It was noted that there should be one, two and three unpaired electrons on each metal atom of CoPc, FePc and PcCrF chains, respectively. Thus halogen‐doped CoPc, FePc and PcCrF are expected to have magnetic properties associated with the unpaired electrons.