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 [CoII(phen)3][CoIII(HATD)2]2·3DMA·3.5H2O (1), and [CoII(terpy)2][CoIII(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 CoIII and CoII ions in an octahedral environment where the CoII 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).