The synthesis and characterization of a new dinuclear iron(III) complex formed during the reaction of the septadentate ligand 2,6-bis[((2-hyroxybenzyl)((1-methylimidazol-2-yl)methyl) amino)methyl]-4-methylphenol (H-3-BIOMP) are reported. The crystal structure of the complex has been solved. The mu-phenolate bis(mu-acetate) diiron(III) complex [Fe-2(BIOMP)(mu-O2CCH3)(2)](ClO4). H2O (5) crystallizes in the space group P2(1)/n with cell dimensions a = 14.983(14) Angstrom, b = 12.341(13) Angstrom, c = 21.391(16) Angstrom, beta = 90.79(7)degrees, V = 3955(6) Angstrom(3), and Z = 4 and was solved for 3493 reflections [I > 3 sigma(I)], giving R = 6.7% and R(W) = 8.3%. The compound consists of two iron(III) ions bridged by a phenolate oxygen atom and coordinated each to phenol, amine, and imidazole pendants of the septadentate ligand as well as bridging acetate ions. The cation has approximately C-2 symmetry. The iron(III) ions are weakly coupled antiferromagnetically (J = -6.34 cm(-1)) and undergo quasireversible one-electron redox processes. The Fen(2)(II)/(FeFeIII)-Fe-II and (FeFeIII)-Fe-II/Fe-2(III) couples are at -0.785 and -0.225 V vs Ag/AgCl, respectively. Compound 5 also displays an intense phenolate-to-iron(III) charge transfer transition at 586 nm (epsilon = 7400 M(-1) cm(-1)/Fe-2). The Fe-57 Mossbauer spectra of 5 were recorded at 295 and 125 K, and both display a single quadrupolar split doublet. The quadrupole splitting (Delta E(Q)) is equal to 1.083(23) mm/s at 295 K and 1.055 (9) mm/s at 125 K. The isomer shift (delta) parameters at 295 and 125 K are 0.406(13) and 0.508(5) mm/s, respectively.