Substituent Effects on Metallo-Supramolecular Coordination Polymers

Dimethyl-substituted bis-terpyridines (L1 and L2) are synthesized as novel ditopic ligand through aldol condensation, Michael-type bis-addition and Suzuki-type cross-coupling. Metallo-supramolecular coordination polymers are obtained by complexation of the bis-terpyridines with metal ions [Ru(II), Fe(II), Co(II)] in suitable solvent. The complexation ratio (1:1) of the ligand with the metal ion in the coordination polymer is confirmed by UV–vis titration experiments and Job’s plot analysis. The binding constants (logK) in the complexation are very high (>9) and the results show that steric hindrance by the methyl groups of the ligand can be ignored in the polymer formation. Their optical, photophysical and electrochemical properties are characterized by UV–vis, luminescence measurements and cyclic voltammetry, respectively, and the substituent effects are discussed. Especially, the luminescence of the Ru(II) polymers is quenched by introduction of the methyl group to bis-terpyridine. Molecular weights of the polymers are estimated by SEC-viscometry-RALS method.