Mssbauer, NMR, Geometric, and Electronic Properties in S = 3/2 Iron Porphyrins
Yan Ling and Yong Zhang*
Iron porphyrins with the intermediate spin S = 3/2 or admixed with S = 5/2 or 1/2 are models for a number of heme protein systems, including cytochromes c′. The 57Fe Mssbauer quadrupole splittings and 1H and 13C NMR chemical shifts have been found to be useful probes of their electronic states. We present the results of the first successful quantum chemical calculations of the Mssbauer and NMR properties in various S = 3/2 iron porphyrin complexes, covering four-, five-, and six-coordinate states and three commonly seen porphyrin conformations: planar, ruffled, and saddled. Several interesting correlations among these useful experimental spectroscopic probes and geometric and electronic properties were discovered. These results should facilitate future investigations of related heme proteins and model systems.