Synthesis, structure and magnetic properties of a new family of chiral metal(II) citramalates

摘要

A new series of chiral carboxylate-bridged complexes of Mn(II), Co(II), and Ni(II) has been synthesized by reaction of M(11) salts with (S)-2-hydroxy-2-methyl-butanedioic acid ((S)-citramalic acid) under solvothermal conditions. The Mn(II) compound I is obtained as a crystalline powder, whereas the Co(II) and Ni(II) compounds (2 and 3 respectively) are obtained as single crystals. All the compounds crystallize in orthorhombic chiral space group P2(1)2(1)2(1). Compounds 2 and 3 are isostructural, and their structure consists in helicoidal chains of M(II) centres linked by carboxylate bridges. The magnetic data indicate a rather weak coupling interaction between paramagnetic centres. The Mn(II) compound 1 exhibits antiferromagnetic ordering at T-N = 2.64 K. The Co(II) and Ni(II) compounds show ferromagnetic interactions within the chains. For 3, the chains couple antiferromagnetically, which leads to a metamagnetic behaviour with TN = 1.69 K. (c) 2006 Elsevier B.V. All rights reserved.