Synthesis, crystal structure and magnetic properties of dimeric Mn < sup > III < /sup > Schiff base complexes including pseudohalide ligands: Ferromagnetic interactions through phenoxo bridges and single molecule magnetism

Abstract

Three new phenoxo-bridged dimeric compounds of MnIII with tetradentate Schiff bases (salpnH2, salmenH2 and acphpnH2) and pseudohalide ligands have been synthesized and characterized by crystallography and dc and ac magnetic measurements. Mn(salpn)NCO (1) and Mn(salmen)N3 (2) exhibit intra-dimer ferromagnetic exchange (J = 0.42(2) cm-1 for 1, J = 0.58(1) cm-1 for 2, over(H, ̂) = - 2 J over(S, ̂)1 over(S, ̂)2). The χmT product of 1 continuously increases upon lowering temperature, reaching a value of 10.01 cm3 mol-1 K at 1.98 K. In the case of 2, the χmT product reaches a maximum value of 7.85 cm3 mol-1 K at 5.82 K and decreases upon further cooling to a value of 6.34 cm3 mol-1 K at 2 K, indicating the operation of inter-dimer antiferromagnetic interactions. Frequency dependence of ac magnetic susceptibility shows single-molecule-magnetic (SMM) behavior in the temperature range 2-10 K for both compounds. In sharp contrast, Mn(acphpn)N3 (3) exhibits antiferromagnetic exchange interactions. salpnH2 = N,N′-bis(salicylidene)-1,3-diaminopropane, salmenH2 = N,N′-bis(salicylidene)-1,2-diaminopropane and acphpnH2 = N,N′-bis(2-hydroxyacetophenone)-1,3-diaminopropane. © 2009 Elsevier Ltd. All rights reserved.