Cobalt(II) compounds [Co(C10C8C2-terpy)(2)](BF(4))(2) (1) and [Co(C12C10C2-terpy)(2)] (BF(4))(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)up arrow = 275K and T(1/2)down arrow = 250K for 1 and T(1/2)up arrow = 307K and T(1/2)down arrow = 296K for 2), and the spin transition is induced by crystal-mesophase transition. The bifunctional materials show synchronizing both spin transition and liquid crystal transition.