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

Two mixed-valence Co( ii )/Co( iii ) complexes of [Co II (phen) 3 ][Co III (HATD) 2 ] 2 ·3DMA·3.5H 2 O ( 1 ), and [Co II (terpy) 2 ][Co III (HATD) 2 ] 2 ·4DMA·H 2 O ( 2 ), (phen = 1,10-phenanthroline, terpy = 2,2′:6′,2′′-terpyridine, H 3 ATD = 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). Two mixed-valence Co( ii )/Co( iii ) complexes of [Co II (phen) 3 ][Co III (HATD) 2 ] 2 ·3DMA·3.5H 2 O ( 1 ) with field induced single-molecule magnet behavior, and [Co II (terpy) 2 ][Co III (HATD) 2 ] 2 ·4DMA·H 2 O ( 2 ) with a gradual thermal spin crossover (SCO).