A semiempirical crystal orbital investigation on the one-dimensional polyferrocenylene system

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Abstract
The band structure of polyferrocenylene has been studied in the crystal orbital formalism based on the tight‐binding approximation; the computational framework is a semiempirical INDO model designed to reproduce the results of double‐zeta ab initio calculations in organic molecules and transition metal compounds. It is shown that 4–6 neighbors are necessary to stabilize the results of the band structure calculations. The total energy of the polymer has been partitioned into elements of physical significance. Metal–metal and metal–ligand potentials have been separated into resonance, exchange, and classical electrostatic contributions. The highest filled band of polyferrocenylene is a ligand π band; Fe 3d bands are predicted at lower energies. The calculated bandwidths span a range between 0.4 to 2.6 eV. Avoided crossing regions in the reciprocal k space lead to a strong metal–ligand intermixing in some of the outer valence bands. It is shown that hole states in partially oxidized polyferrocenylene are probably unstable against the formation of a state with trapped valences. The close relation between this behavior and the soliton formalism is discussed. The various computational results are compared with experimental data.