Incorporation of spin-crossover cobalt(II) complexes into conducting metallopolymers: Towards redox-controlled spin change

Abstract

Metal complexes from cobalt(II/III) ions with two tridentate ligands and the corresponding conducting metallopolymers have been synthesized, characterized and subjected to magnetic studies which revealed a redox-controlled spin change. These complexes were designed to contain both a possible spin-crossover metal complex core and an electropolymerizable group for the production of the corresponding conducting metallopolymers. SQUID magnetic measurements revealed a gradual thermal spin crossover (T½ = 170 K) and a low spin state up to 400 K for the two complexes with terpyridine ligand cores chelating to Co(II) and Co(III) centers, respectively, supporting the viability of a spin change from paramagnetic (Co(II), S = 3/2) to diamagnetic (Co(III), S = 0) states via redox chemistry. We have also demonstrated that the reported cobalt(II) complexes can undergo a facile polymer growth process under electropolymerization conditions. Electrochemical studies revealed that the Co(II) and Co(III) metal centers in poly-CoIIL1 could be reversibly interconverted, which demonstrates that the magnetic properties of the conducting metallopolymers can be switched between paramagnetic and diamagnetic.