Structures and properties of octaethylporphinato(phenolate)iron(III) complexes with NH⋯O hydrogen bonds: modulation of Fe–O bond character by the hydrogen bond

Iron(III) porphinate complexes of phenolate that have NH⋯O hydrogen bonds on the coordinating oxygen, [FeIII(OEP){O-2,6-(RCONH)2C6H3}] (R = CF3 (1), CH3 (3)) and [FeIII(OEP)(O-2-RCONHC6H4)] (R = CF3 (2), CH3 (4)) (OEP = 2,3,7,8,12,13,17,18-octaethyl-21H, 23H-porphinato), were synthesized and characterized as models of heme catalase. The presence of NH⋯O hydrogen bonds was established by their crystal structures and IR shifts of the amide NH band. The crystal structure of 1 shows an extremely elongated Fe–O bond, 1.926(3) Å, compared to 1.887(2) Å in 2 or 1.848(4) Å in [FeIII(OEP)(OPh)]. The NH⋯O hydrogen bond decreases an electron donation from oxygen to iron, resulting in a long Fe–O bond and a positive redox potential.