Antiferromagnetic spin couplings between iron ions in iron—sulfur clusters. A localized picture by the spin vector model

Abstract

Antiferromagnetic spin correlation effects for iron—sulfur clusters in ferredoxins were investigated on the basis of ab initio UHF and Heisenberg models. The electronic structures with two (helical) and three (general) dimensional spin modulations are found to be the ground states for these species because of the near degeneracies between several MOs in the frontier region. The spin vector model is found to be useful for a localized representation of complex antiferromagnetic spin couplings between the high-spin iron atoms (ions) in the clusters.