A novel functional nitronyl nitroxide and its copper and cobalt complexes: Synthesis, structures and magnetic properties

Abstract

Four new metal complexes derived from a functional nitronyl nitroxide ligand, 2-(6-bromo-3-pyridyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (NIT-6Br-3Py) and M(hfac)2+ (M2+ = Cu2+, Co2+; hfac = hexafluoroacetylacetonate), [(Cu(hfac)2)3(NIT-6Br-3Py)2] (1), [Cu(hfac)2NIT-6Br-3Py]n (2), [Co(hfac)2(H2O)NIT-6Br-3Py] (3) and [(Co(hfac)2)2(NIT-6Br-3Py)2] (4) have been synthesized and characterized. In complex 1, the NIT-6Br-3Py ligand acts as bridging ligand to link three Cu(II) ions leading to {Cu3} complex while complex 2 displays a 1D-chain structure. Complex 3 possesses mono-nuclear structure and 4 is a four-spin complex with a dimeric structure, where the NIT-6Br-3Py ligand links Co ions via the oxygen atom of NO group and the nitrogen atom from pyridine ring. Magnetic studies show that the antiferromagnetic interactions are dominated in complexes 1, 3 and 4, while there exist strong ferromagnetic interactions between CuII and coordinated nitronyl nitroxide radical ligand in complex 2.