Aliphatic dicarboxylate ligands assemble weakly coupled molecular pairs of [Mn III] 2 units

Seven new tetranuclear Mn III compounds have been obtained by assembling two dinuclear units, [{Mn(L)(NN)} 2(μ-O)] 4+, with aliphatic dicarboxylate ligands COO(CH 2) nCOO 2-: succinato (n = 2, C4 2-), glutarato (n = 3, C5 2-) and adipato (n = 4, C6 2-), and NN = 2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen). The general formula for these compounds is [{Mn(L)(NN)} 4(μ-Cm) 2(μ-O) 2]X 4 [X = ClO 4, NN = bpy and Cm = C4 (1), C5 (2) and C6 (3); X = ClO 4, NN = phen and Cm = C4 (4), C5 (5) and C6 (6); X = NO 3, NN = bpy and Cm = C5 (7)]. Compounds 1, 2 and 4 were characterized by X-ray diffraction, which confirmed the assembly of two dinuclear entities. The magnetic properties of the seven compounds were studied and the results indicate that the main interaction takes place within the dinuclear units. Compound 4 shows a dominant ferromagnetic coupling with J = 4.0 cm -1, while the rest of compounds display antiferromagnetic couplings with J values of -2.8 (1), -1.9 (2), -3.3 (3), -0.3 (5), -0.4 (6) and -9.3 cm -1 (7), which are all in agreement with magneto-structural correlations. In the case of compound 4, a weak but significant antiferromagnetic coupling of the S = 4 [Mn III] 2 subunits with an interaction constant of -0.9 cm -1 was observed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.This work was supported by the Spanish Ministerio de Ciencia e Innovación (MICINN) through project CTQ2009-07264/BQU and PhD grant BES-2007-15668 (to V. G.) and the Comissió Interdepartamental de Recerca i Innovació Tecnològica of la Generalitat de Catalunya (CIRIT) (2009-SGR1454).Peer Reviewe