TOWARDS A MODEL FOR THE OXIDIZED FORM OF PURPLE ACID-PHOSPHATASE - CRYSTAL-STRUCTURE AND MAGNETIC-PROPERTIES OF A BINUCLEAR IRON(III) COMPLEX CONTAINING PHOSPHATE LIGANDS

A novel binuclear iron(III) complex [{FeL[O2P(OPh)(2)]}(2)][ClO4](2) w as synthesized and characterized by X-ray single-crystal structure ana lysis, where HL is bis(benzimidazol-2-ylmethyl) (2-hydroxyethyl)amine. The crystals are triclinic, space group <P(1)over bar>, with a = 11.5 23(9),b = 11.809(6), c = 13.406(4) Angstrom, alpha = 68.52(4), beta = 71.41(5), gamma = 71.85(6)degrees and Z = 1. The structure shows that the iron(LII)ions are bridged by the oxygen atoms of two L ligands and a phosphate ligand is terminally co-ordinated to each iron(III). Magn etic susceptibility measurements in the range 4.2-300 K and subsequent calculations based on an isotropic Heisenberg model suggest antiferro magnetic coupling between the iron(III) ions with J = -17.5 cm(-1).