Low-spin bis(2-methylimidazole)(octaethylporphyrinato)iron(III) chloride (perp-[Fe(OEP)(2-MeHIm)2]Cl):: A consequence of hydrogen bonding?

The synthesis and characterization of low-spin bis(2-methylimidazole)(octaethylporphyrinato)iron(III) chloride (perp[Fe(OEP)(2-MeHIm)(2)]Cl) is reported. The structure shows that the cation is a low-spin species with two imidazole ligands having a relative perpendicular orientation. The porphyrin core is very ruffled, which leads to shortened equatorial bonds of 1.974(4) angstrom and slightly elongated axial Fe-N bond lengths of 2.005(10) angstrom that are about 0.02 angstrom shorter and 0.03 angstrom longer, respectively, in comparison to bis-imidazole ligated iron(III) species with parallel oriented axial ligands. A one-dimensional hydrogen-bond chain is formed between chloride anions and uncoordinated imidazole nitrogen atoms. Compared with paral-[Fe(OEP)(2-MeHIm)(2)]ClO4, hydrogen bonding may play an important role in the differences in the two structures. Mossbauer spectra show broadened quadrupole doublets with quadrupole splittings of 1.81 mm/s at RT and 1.94 mm/s at 20 K. The isomer shift ranges from 0.26 to 0.36 mm/s. These confirm that the title complex is a low-spin iron(III) species with the ground state (d(xy))(2)(d(xz),d(yz))(3). Crystal data: monoclinic, space group P2(1)/c, a = 14.066(3) angstrom, b, 20.883(4) angstrom, c = 19.245(4) angstrom, beta = 109.67 degrees, and Z = 4.