Electronic structures of polymers, ferrocene (CP2Fe, Cp = eta(5)-C5H5) in the main chain, were examined using the tight-binding crystal orbital method. Attention was focused on the manner in which the band structures of the polymers were influenced by the bridging moieties between the ferrocenes. Ferrocene-containing polymers with unsaturated carbon bridges possessed relatively wide bandwidths of both the highest occupied band and the lowest unoccupied band. Although the pi conjugation was broken at the iron atoms, the unsaturated carbon bridges could form limited delocalization of the pi electrons between the neighbouring Cp rings, via the bridging moieties. (c) 2006 Elsevier B.V. All rights reserved.