Crystallographic identification of a series of manganese porphyrin complexes with nitrogenous bases.

Abstract

Studying the axial ligation behavior of metalloporphyrins with nitrogenous bases helps to better understand not only the biological function of heme-based protein systems, but also the catalytic properties of porphyrin-based reaction sites in other biomimetic synthetic support environments. Unlike iron porphyrin complexes, little is known about the axial ligation behavior of Mn porphyrins, particularly in the solid state with Mn in the +3 oxidation state. Here, we present the syntheses and crystal and molecular structures of three new high-spin manganese(III) porphyrin complexes with the different amine-based axial ligands imidazole (im), piperidine (pip), and 1,4-diazabicyclo[2.2.2]octane (DABCO), namely bis(imidazole)(5,10,15,20-tetraphenylporphyrinato)manganese(III) chloride chloroform disolvate, [Mn(C44H28N4)(C3H4N2)2]Cl·2CHCl3 or [Mn(TPP)(im)2]Cl·2CHCl3 (TPP = 5,10,15,20-tetraphenylporphyrin), (I), bis(piperidine)(5,10,15,20-tetraphenylporphyrinato)manganese(III) chloride, [Mn(C44H28N4)(C5H11N)2]Cl or [Mn(TPP)(pip)2]Cl, (II), and chlorido(1,4-diazabicyclo[2.2.2]octane)(5,10,15,20-tetraphenylporphyrin)manganese(III)-1,4-diazabicyclo[2.2.2]octane-toluene-water (4/4/4/1), [Mn(C44H28N4)Cl(C6H12N2)]·C6H12N2·C7H8·0.25H2O or [Mn(TPP)Cl(DABCO)]·(DABCO)·(toluene)·0.25H2O, (IV). A fourth complex, chlorido(pyridine)(5,10,15,20-tetraphenylporphryinato)manganese(III) pyridine disolvate, [Mn(C44H28N4)Cl(C5H5N)]·2C5H5N or [Mn(TPP)Cl(py)]·2(py), (III), acquired using different crystallization methods from published data, is also reported and compared to the previous structures.