LAUSR

Abstract Taking advantage of the multi-functional m-FPhH3IDC ligand, two highly stable Co(II) complexes, namely, [Co(m-FPhH2IDC)2 (2,2′-bipy)]·H2O (1) and [Co(m-FPhH2IDC)2 (phen)]·H2O (2) (m-FPhH3IDC ​= ​2-(m-fluoro)phenyl-4,5-imidazole dicarboxylic acid, 2,2′-bipy ​= ​2,2′-bipyridine, phen ​= ​1,10-phenanthroline) have been hydrothermally synthesized and structurally characterized. 1 and 2 were found to be stable in aqueous solution having pH values ranging from 1 to 11 as well as boiling water. The results of structural analysis show that abundant hydrogen-bonding networks in 1 and 2 formed by water molecules, carboxyl and imidazole groups exist which are beneficial for the transfer of protons. Therefore, the temperature- and humidity-dependent proton conduction properties of the two complexes were investigated in detail. 1 and 2 have the optimal proton conductivities of 8.15 ​× ​10-4 ​S ​cm-1 and 1.31 ​× ​10-5 ​S ​cm-1 at 373 ​K under 98% RH, respectively, which can be compared to the reported imidazole dicarboxylate-based complexes. In addition, the proton conducting mechanism was studied in detail.