Molecular structures and magnetism of Mn-12 nanomagnets containing the 3-thiophenecarboxylate ligand

Abstract

The new Mn-12 single-molecule magnets containing thiophenyl ligands, [Mn12O12(O2CC4H3S)(16)(HO2CC4H3S)-(H2O)(2)]center dot 5CH(2)CI(2)(1) and [Mn12O12(O2CC4H3S)(16)(H2O)(4)]center dot 6CH(2)CI(2)center dot 2H(2)O (2), have been synthesized by hgand-substitution reactions of 3-thiophenecarboxylic acid and [Mn12O12(O2CCH3)(16)(H2O)(4)] and investigated by magnetic measurements with a SQUID magnetometer. The X-ray analysis of 1 shows five-coordination geometry around the Mn-III ion due to the unusual coordination of 3-thiophenecarboxylic acid to the Mn-III ion. Compound 1 displays two different rates of magnetization relaxation, which are faster than that of compound 2 because of structural distortion in the Mn-12 complex of 1. Magnetic susceptibility measurements on 1 and 2 give the following parameters: U-eff (the faster relaxation form of 1) = 51.81 K, 1/tau(0) = 1.90.10(8) S-1; U-eff (the slower relaxation form of 1) = 66.44 K, 1/tau(0) = 1.50.10(8) s(-1); U-eff(2) = 67.09 K, 1/tau(0) = 1.32.10(8) s(-1). (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006.