FULL PAPER DOI: 10.1002/ejic.201200027 Aliphatic Dicarboxylate Ligands Assemble Weakly Coupled Molecular Pairs of [Mn III ] 2 Units Verónica Gómez,* [a] Montserrat Corbella,* [a] Gema Fernández, [a] Olivier Roubeau, [b] Simon J. Teat, [c] and Miguel A. Maestro [d] Keywords: Manganese / Magnetic properties / Molecular assembly Seven new tetranuclear Mn III compounds have been ob- tained by assembling two dinuclear units, [{Mn(L)(NN)} 2 (μ- O)] 4+ , with aliphatic dicarboxylate ligands COO(CH 2 ) n - COO 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 com- pounds 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 charac- terized by X-ray diffraction, which confirmed the assembly of Introduction Since the discovery of Mn-catalases, [1] enzymes that are responsible for the disproportionation of H 2 O 2 to give O 2 and H 2 O in some microorganisms, several dinuclear Mn III complexes with carboxylate ligands have been reported in the literature. [2] These compounds have a [Mn 2 (μ-O)(μ- RCOO) 2 ] 2+ core and display weak magnetic interactions, either ferro- or antiferromagnetic. On the other hand, a number of dinuclear Mn III complexes present single mole- cule magnet (SMM) behavior that results from both ferro- magnetic interactions and the close to parallel alignment of the Mn III anisotropy axes. [3] As proposed, and already demonstrated, such small complexes are good building blocks for the formation of extended assemblies aimed at ordered arrays of isolated SMMs, molecule based 3D mag- nets or multifunctional systems. [4] As in metal organic [a] Department de Química Inorgànica, Universitat de Barcelona, Av. Diagonal 645, 08028 Barcelona, Spain Fax: +34-934-907-725 E-mail: veronica.gomez@qi.ub.es montse.corbella@qi.ub.es [b] Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC and Universidad de Zaragoza, Plaza San Francisco s/n, 50009, Zaragoza, Spain [c] Advanced Light Source, Berkeley Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA [d] Departamento de Química Fundamental, Universidade da Coruña, 15071 A Coruña, Spain Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/ejic.201200027 Eur. J. Inorg. Chem. 2012, 2359–2367 © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2359 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. Com- pound 4 shows a dominant ferromagnetic coupling with J = 4.0 cm –1 , while the rest of compounds display antiferromag- netic 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. framework (MOF) chemistry, polycarboxylate ligands are among the most common candidates for the realization of this assembly process. More recently, molecules containing two well-defined magnetic units have been proposed as can- didates for the implementation of spin-based quantum computing. [5] One of the requirements, among other more stringent conditions, is the presence of an antiferromagnetic interaction between the two subunits much smaller than those within the individual subunits. Here again dicarboxyl- ates clearly represent one of the synthetic means to link chemically and weakly coupled magnetically magnetic building blocks. To test the potential of such ligands for assembling two dinuclear Mn III units into tetranuclear com- plexes, three aliphatic dicarboxylic acids, COOH(CH 2 ) n - COOH, were chosen: succinic acid (n = 2, H 2 C4), glutaric acid (n = 3, H 2 C5) and adipic acid (n = 4, H 2 C6). So far, only three compounds with Mn III ions have been reported with these ligands, all of them contain the succinato ligand, two are one-dimensional systems and the third is a Mn II Mn III tetranuclear complex. [6] Herein, we report the synthesis and characterization of the tetranuclear Mn III compounds 1–7 containing aliphatic dicarboxylate ligands: succinato (C4 2– ), glutarato (C5 2– ) and adipato (C6 2– ). The general formula for these com- pounds is [{Mn(L)(NN)} 4 (μ-Cm) 2 (μ-O) 2 ]X 4 , X = ClO 4 , NN = 2,2'-bipyridine (bpy) and Cm = C4 (1), C5 (2), C6 (3); X = ClO 4 , NN = 1,10-phenanthroline (phen) and Cm = C4 (4), C5 (5), C6 (6); X = NO 3 , NN = bpy and Cm = C5 (7).