Synthesis and characterization of (cryptand-222)potassium (2-methylimidazolato)(meso-tetraphenylporphinato)ferrate(II)–2-methylimidazole–tetrahydrofuran (1/1/2)

Abstract

Metalloporphyrin complexes containing an additional imidazole ligand can provide information about the effect of deprotonation or hydrogen bonding on the axial histidine unit in heme proteins. The title high-spin five-coordinate imidazolate-ligated iron(II) porphyrinate, [K(C18H36N2O6)][Fe(C4H5N2)(C44H28N4)]·C4H6N2·2C4H8O, has been synthesized and investigated. The solvated salt crystallizes with one 2-methylimidazole molecule, two tetrahydrofuran solvent molecules and a potassium cation chelated inside a cryptand-222 (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) molecule. The imidazolate ligand is ordered. The average Fe—Np (Np is a porphyrin N atom) bond length is 2.113 (11) Å and the axial Fe—NIm (NIm is an imidazolate N atom) is 2.0739 (13) Å. The out-of-plane displacement of the FeII atom from the 24-atom mean plane is 0.6098 (5) Å, indicating an apparent doming of the porphyrin core.