Stabilization of Long-Lived Metastable State in Long Alkylated Spin-Crossover Cobalt(II) Compound

The A mixed crystal compound [Co0.8Fe0.2(C16-terpy)2](BF4)2 (2) (C16-terpy is 4′-hexadecyloxy-2,2′:6′,2′′-terpyridine) with long alkyl chains was prepared by mixing [Co(C16-terpy)2](BF4)2 (1), which exhibits unique magnetic behavior, and the diamagnetic iron(II) compound [Fe(C16-terpy)2](BF4)2 (3). The long-lived metastable state in the frozen-in effect was observed for the first time in the spin-crossover cobalt(II) compound 2. Furthermore, relaxation from metastable to stable states was very slow because of a large structural transition resulting from the long alkyl chains.