Three composites composed of the cobalt terpyridine complex [CoII(MeO-terpy)2] and the diblock copolypeptide amphiphiles 1 and 2 or the polypeptide 3 (including glutamic acid and leucine) were prepared. Supramolecular structures such as rectangular morphologies were obtained from composites of 1 and 2. A perfectly reversible reverse spin transition was successfully generated in the case of composites made with 1.