Publication 745

IQUIR (Instituto de Química Rosario), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, S2002LRK Rosario, Argentina
Laboratoire Electrochimie Moléculaire-UMR CNRS 7591, University of Paris Diderot, Sorbonne Paris Cité15 rue Jean de Baïf, 75251 Paris, Cedex 13, France
ICMMO-UMR 8182, Equipe Chimie Inorganique, Université Paris-Sud, 91405 Orsay, France
Institut de Chimie de Toulouse, FR 2599, 118 Route de Narbonne, F-31062 Toulouse, France
CNRS, LCC (Laboratoire de Chimie de Coordination) and UPS, INPT, LCC, Université de Toulouse, 205 route de Narbonne, F-31077 Toulouse, France

Two new tri-Mn^III complexes of general formula [Mn₃L₂(µ-OH)(OAc)]ClO₄ (H₃L = 1-[N-(2-pyridylmethyl),N-(2-hydroxybenzyl)amino]-3-[N'-(2-hydroxybenzyl),N'-(4-X-benzyl)amino]propan-2-ol; 1ClO₄, X = Me; 2ClO₄, X = H) have been prepared and characterized. X-ray diffraction analysis of 1ClO₄ reveals that the complex cation possesses a Mn₃(µ-alkoxo)₂(µ-hydroxo)(µ-phenoxo)⁴⁺ core, with the three Mn atoms bound to two fully deprotonated N₃O₃ chelating L^3–, one exogenous acetato ligand, and one hydroxo bridge, the structure of which is retained upon dissolution in acetonitrile or methanol. The three Mn atoms occupy the vertices of a nearly isosceles triangle (Mn1···Mn3 = 3.6374(12) Å, Mn2···Mn3 3.5583(13) Å, and Mn1···Mn2 3.2400(12) Å), with one substitution-labile site on the apical Mn ion occupied by terminally bound monodentate acetate. Temperature-dependent magnetic susceptibility studies indicate the presence of predominant antiferromagnetic intramolecular interactions between Mn^III ions in 1ClO₄. Complexes 1ClO₄ and 2ClO₄ decompose H₂O₂ at comparable rates upon initial binding of peroxide through acetate substitution, with retention of core structure during catalysis. Kinetic and spectroscopic studies suggest that these complexes employ the [Mn–(µ-oxo/aquo)–Mn]⁴⁺ moiety to activate peroxide, with the additional (µ-alkoxo)(µ-phenoxo)Mn(µ-alkoxo) metallobridge carrying out a structural function.