Slow magnetic relaxation and spin crossover behavior in two mixed-valence Co(ii)/Co(iii) complexes

Abstract

Two mixed-valence Co(II)/Co(III) complexes of [Co^II(phen)₃][Co^III(HATD)₂]₂·3DMA·3.5H₂O (1), and [Co^II(terpy)₂][Co^III(HATD)₂]₂·4DMA·H₂O (2), (phen = 1,10-phenanthroline, terpy = 2,2′:6′,2′′-terpyridine, H₃ATD = azotetrazolyl-2,7-dihydroxynaphthalene, DMA = N,N-dimethylacetamide) were synthesized and their crystal structures were characterized. Crystal structure analyses reveal that complexes 1 and 2 consist of Co^III and Co^II ions in an octahedral environment where the Co^II ion is coordinated by three phen ligands and two terpy ligands, respectively. Magnetic measurements show that complex 1 displays field induced single-molecule magnet behavior, whereas 2 undergoes a gradual thermal spin crossover (SCO).