Spin Transition Induced by Mesophase Transition in the Cobalt(II) Compounds with Branched Alkyl Chains

Abstract

Cobalt(II) compounds [Co(C10C8C2-terpy)2](BF4)2 (1) and [Co(C12C10C2-terpy)2](BF4)2 (2) (CxCyCz-terpy = 4′-5″′-Alkyl-1″′-alkoxy-2,2′:6′,2″-terpyridine) with branched alkyl chains, based on a terpyridine frame, was synthesized. The cobalt(II) compounds 1 and 2 exhibit the spin transition between low-spin and high-spin with thermal hysteresis loop at the liquid crystal transition temperature (T 1/2↑ = 275 K and T 1/2↓ = 250 K for 1 and T 1/2↑ = 307 K and T 1/2↓ = 296 K for 2), and the spin transition is induced by crystal-mesophase transition. The bifunctional materials show synchronizing both spin transition and liquid crystal transition.