A cobalt(II) complex based on imidazole dicarboxylate ligand with high proton conductivity

A Co(II) complex, [Co(HPhIDC)(4,4′-bipy)] was prepared in the presence of a imidazole dicarboxylic ligand H 3 PhIDC and 4,4′-bipy ligand under hydrothermal conditions. It exhibits excellent water and chemical stability, and interesting proton conductive properties. The resulting metal complex showed high proton conductivity with a maximum value of 1.35 × 10 −4 S·cm −1 at 98% RH and 373K. • A new imidazole dicarboxylic acid-based Co(II) complex was successfully synthesized. • The complex exhibits good thermal, water and chemical stabilities. • The complex shows high proton conductive properties. In order to search for new crystalline proton conductive materials, a highly stable Co(II) complex, namely, [Co(HPhIDC)(4,4′-bipy)] ( 1 ) (H 3 PhIDC = 2-phenyl-4,5-imidazole dicarboxylic acid, 4,4′-bipy = 4,4′-bipyridine) has been successfully synthesized under hydrothermal conditions and structurally characterized. 1 exhibits high thermal, water and chemical stabilities, which promoted us to investigate its proton conductivity in water vapor. The results showed that proton conductivity of 1 was dependent on temperature and relative humidity (RH). The optimal proton conductivity of 1 reaches up to a highest value of 1.35 × 10 −4 S·cm −1 at 373 K under 98% RH. According to the E a value, the proton conduction mechanism of 1 maybe a combination of Grotthuss and Vehicle mechanisms at 98% RH and major Vehicle mechanism at 75% RH.