Proton conductive properties of one water-stable nickel(II) supramolecule bearing tri-pyridyl and tri-carboxylate ligand

Abstract

The construction of highly stable complexes using azacyclic carboxylate ligands is an important way to obtain crystalline proton-conducting materials with high performance. In this paper, one three-dimensional supramolecule, [Ni(H2ttp)2]⋅3H2O (1) [H3ttp = 4-(2,4,6-tricarboxyphenyl)-2,2′,6,2′′-terpyridine] has been prepared according to literature approach with slight modification. Firstly, its molecular structure was determined by powder X-ray diffraction, infrared spectroscopy, and elemental analysis, followed by a thermogravimetric determination to confirm its thermal and water stability. The N2 and water H2O adsorption abilities were also measured. Electrochemical experiments have shown 1 to be a typical temperature and humidity-dependent proton conductor with an optimum proton conductivity of 4.00 × 10−4 S/cm (98% RH/100 °C). A large number of uncoordinated carboxylate units and crystalline water molecules, as well as the H-bonding networks inside the framework, provide effective channels for proton transportation. The proton-conductive mechanism was further postulated following the calculated value of activation energy.