Ferrous porphyrins with an “unusually” large quadrupole splitting

High-spin ferrous metalloporphyrins Fe^II(NCH₃TPP)Cl, Fe^II(NCH₃TPP)Br, Fe^II(NCH₃TPP)ClO₄, and Fe^II(NCH₃OEP)Cl(NCH₃TPP-N-methyltetraphenylporphyrin, NCH₃OEP-N-methyloctaethylporphyrin) have been characterized by Mössbauer spectroscopy. Values ofIS (0.8 mm/s versus α-Fe) typical for high-spin ferrous porphyrin and very large quadrupole splittings (?4 mm/s) have been observed. Iron(II) N-methylporphyrins should be readily detected in proteins by means of Mössbauer spectroscopy. Such parameters are similar to those of symmetrical anionic five coordinate high-spin porphyrins Fe^II(TPP)X]^? (X-halide).