Synthesis, structure, magnetic, spectroscopic and electrochemical behaviour of chloro-iron(III) and -manganese(III) complexes of 2,3,7,8,12,13,17,18-octakis(ethylsulfanyl)-5,10,15,20-tetraazaporphyrin

Abstract

The complexes [M(oespz)Cl][M = Mn^III or Fe^III; oespz = 2,3,7,8,12,13,17,18-octakis(ethylsulfanyl)-5,10,15,20-tetraazaporphyrinate dianion] have been prepared and their structures determined. The isomorphous structures consist of stacked dimers. Monomers, within each dimer, are slipped and faced in trans fashion respect to the M–Cl bond. Weak interdimer interactions arise from Cl ⋯ S contacts. Intradimer interactions are provided by relatively long M ⋯ S and N (pyrrole)⋯ S contacts. Magnetic susceptibility measurements revealed that [Mn(oespz)Cl] is a high-spin (S= 2) complex with weak antiferromagnetic coupling between the Mn^III. The toluene frozen-glass EPR spectrum of [Fe(oespz)Cl] seems to be consistent with a S= ground state, whereas the polycrystalline powder EPR spectrum at 4.2 K and magnetic susceptibility data are better rationalized in terms of a S=5//₂ and ½ admixture. The crowding of the UV/VIS spectra of both complexes and the red shift of the Soret and Q bands of [Fe(oespz)Cl] are related to the effects of the peripheral ethylsulfanyl groups on the porphyrazinato ring. Both compounds show characteristic NIR absorptions. Voltammetric data are consistent with the tendency of the porphyrazinate ligand to stabilize the lower oxidation states of metals relative to phthalocyanines and porphyrins.