Theoretical Studies of the Ground and Excited States of a Model of the Active Site in Oxidized and Reduced Rubredoxin1

Using the system Fe(SH)4 to model the active site of rubredoxin, we have carried out ab initio quality Hartree-Fock and extensive configuration interaction studies of the ground and excited states of both the oxidized and reduced systems. We have established that the ground state is high spin in both redox forms and find charge distributions in agreement with Möss-bauer studies. Based on calculated excitation energies and intensities, we have assigned all the spectral features below 3 eV including d-d spin-allowed, d-d spin-forbidden, and ligand to metal charge-transfer bands.