Electronic ground states of iron porphyrin and of the first species in the catalytic reaction cycle of cytochrome P450s

Electronic structures of iron(II) and iron(III) porphyrins are studied with density functional theory (DFT) using the GGA exchange functional OPTX in combination with the correlation functional PBE (OPBE) and with the correlation functional Perdew (OPedrew) together with a triple zeta-type basis set. These functionals are evaluated against other functionals for their performance in calculating relative energies for the various electronic states of both the iron porphyrins.