Microwave-assisted synthesis, crystal structure and properties of a disc-like heptanuclear Co(II) cluster and a heterometallic cubanic Co(II) cluster

Abstract

The reaction of Co(ClO₄)₂·6H₂O with a disodium 2-[(2-hydroxy-3-methoxy-enzylidene)-amino]-ethanesulfonic acid (Na₂L) in a mixture solution (methanol : acetonitrile = 1 : 1 (v/v)) or an acetonitrile solution under microwave and controlled pressure/temperature, or solvothermal conditions leads to the formation of two completely different Co^II complexes: heptanuclear cluster [Co₇(immp)₆(CH₃O)₆]·2ClO₄ (1) (immp is 2-iminomethyl-6-methoxy-phenolic anion) and tetra-heteronuclear cubane cluster [NaCo₃(L)₃(CH₃CN)₃(OH)]₂·CH₃CN (2). The microwave-assisted reactions can improve the reaction rate and yield compared to simple solvothermal synthesis. The magnetic investigation shows that complexes 1 and 2 exhibit a ferromagnetic coupling between the Co^II ions. AC susceptibilities of the two complexes reveal no frequency-dependent out-of-phase signals and the corresponding magnetic properties were discussed.