A proton conductive hydrogen-bonded framework incorporating 18-crown-6-ether and dicarboxy-o-terphenyl moieties

Abstract

To date, proton-conducting organic crystalline materials based on crown ethers have rarely been investigated. In this work, we reveal that flexible organic 18-crown-6 derivatives with one or two 4,4′-dicarboxy-o-terphenyl (CT) groups formed four kinds of crystalline frameworks: 1CT-18C6-I (P2₁/n), 2CT-18C6-I (P), 2CT-18C6-II (P) and 2CT-18C6-III (Cmc2₁). Single crystal X-ray diffraction analysis clearly suggested that the water molecules were involved a hydrogen-bonded network for two frameworks. In particular, a unique one-dimensional (1D) water pathway had formed in 2CT-18C6-III and the activation energy was evaluated by Arrhenius plots to be 0.14 eV, indicating that the proton jumps from H₃O⁺ to the neighboring H₂O in the hydrogen-bonded network of 2CT-18C6-III.