Proton-Conductive Coordination Polymers Based on Diphenylsulfone-3,3'-disulfo-4,4'-dicarboxylate with Well-Defined Hydrogen Bonding Networks.

The diphenylsulfone-3,3'-disulfo-4,4'-dicarboxylic acid (H4-DPSDSDC) ligand and its coordination polymers, [K2Zn(C14H6S3O12)(H2O)4]n (1) and {[Cu3(μ3-OH)2(C14H6S3O12)(H2O)3(DMF)]·3(H2O)}n (2) (C14H6S3O12 = diphenylsulfone-3,3'-disulfo-4,4'-dicarboxylate), were synthesized. The Zn(H2O)4 units in 1 are connected by DPSDSDC4- ligands to generate a one-dimensional (1D) chain, which is bridged by K-O bonds associated with bridging water molecules and sulfonate groups to yield a two-dimensional (2D) layer. In 2, the 1D hydroxyl-bridging Cu(II) chains are connected by DPSDSDC4- ligands to give a 2D layer. The 2D layers in 1 and 2 are further connected by interlayered hydrogen bonds to give three-dimensional (3D) frameworks. Compounds 1 and 2 have good conductivities of 1.57 × 10-4 and 5.32 × 10-5 S cm-1, respectively. Continuous well-defined hydrogen bonding networks associated with water molecules, sulfonate groups, and carboxylate groups were observed in compounds 1 and 2. Such hydrogen bonding networks provide hydrophilic domains and effective transfer pathways for protons. Here, we present elegant examples of a precise determination of the pathways for proton transport.