Theoretical Characterization of the Electronic and Spin Structures for Iron–Sulfur Cubane in Reduced High-Potential Iron–Sulfur Proteins Using Density Functional Theory

Abstract

In this work, density functional theory and natural bond orbital analysis are used to investigate the electronic structures of the [4Fe-4S] cluster in reduced high-potential iron–sulfur proteins. Calculated 3d-orbital occupancies of Fe atoms in the [4Fe-4S] cluster revealed a spin structure with two ferromagnetically coupled [2Fe-2S]+ subclusters that are antiferromagnetically coupled to each other. In addition, the chemical bonds between S–Fe were found to form primarily through the donation of electrons from S to Fe atoms.