Binuclear manganese(III) complexes with carboxylate bridges: Synthesis, structure, electrochemistry and magnetic properties
摘要:
A series of mu-oxo, mu-carboxylato binuclear manganese(III) complexes derived from bipy, phen and different carboxylate ligands have been prepared and characterized by IR and UV-vis spectroscopies, cyclic voltammetry, magnetic susceptibility and the X-ray crystallography. The electronic spectra of all the complexes show very similar features consisting of two absorptions in the visible region, one high intensity LMCT band and two intra-ligand transitions in the UV region. The cyclic voltammograms of the complexes exhibit four steps in most cases, each consisting of a one-electron transfer reaction. These probably correspond to Mn-2(III) <-> (MnMnIII)-Mn-IV <-> Mn-2(IV) oxidation and Mn-2(III) <-> (MnMnII)-Mn-III <-> Mn-2(OO) reduction processes. The structure of complex 2 has been determined by the X-ray crystallography and consists of a binuclear [Mn-2(bipy)(2)(mu-O)(mu-OOCR)(2)(NO3)(H2O)](+) cation (R = CH2Cl) with a ClO4- anion. Low temperature magnetic susceptibility measurements show that there is a weak ferromagnetic interaction in 1 (R = Ph) (J = +0.43 cm(-1)) and a weak antiferromagnetic interaction between the metal centers in 2 (R = CH2Cl) (J = -0.15 cm(-1)). (C) 2005 Elsevier Ltd. All rights reserved.