Preparation, characterization, and electrochromic properties of novel Co(II)-bis-2,2’:6’,2”-terpyridine metallo-supramolecular polymers

A rich variety of novel ditopic bis-terpyridines, by symmetric and unsymmetric introduction of functional groups in the pyridine rings, as well as tuning the spacers for bridging the two terpyridine moieties, is described. These bis-terpyridines are useful ligands for developing new metallo-supramolecular materials with novel functions, as well as for investigating the structure–property relationships. In order to investigate the structural factors of bis-terpyridine based metallo-supramolecular materials, such as the functional groups in the ring periphery of the ligands and the spacers between the two terpyridine coordination components, several different types of CoII-bis-terpyridine supramolecular polymers were prepared from various bis-terpyridine functional modules and Co(OAc)2. The absorption and the electrochemical behavior of these new supramolecular polymers were studied by UV/Vis spectroscopy and differential pulse voltammetry (DPV), respectively. The results showed that the introduction of electron donating groups at the pyridine ring affects remarkably the charge transfer and electrochemical properties of the coordination polymers. In addition, the electrochromic properties of the coordination polymers were also studied. Significant color change and high reversibility were observed from these polymers.