Tetranuclear Silver(I) Clusters Showing High Ionic Conductivity in a Bicontinuous Cubic Mesophase

The synthesis and characterization of tetranuclear silver triazole metallomesogens, [Ag4(L4-Cn)6]­[BF4]4 (L4-Cn = 4-alkyl-1,2,4-triazoles where Cn stands for CnH2n+1 with n = 12, 14, 16, and 18), are reported. Upon heating, a phase transition sequence of Cr → SmC → Cub → SmA → isotropic liquid is observed for all of these compounds. Depending on the alkyl chain length, two types of cubic phases are found in this series of compounds. Those with shorter alkyl chains (n = 12 and 14) exhibit a micellar cubic phase, whereas long alkyl chains (n =16 and 18) show a bicontinuous cubic phase. Superior ionic conductivity at the bicontinuous cubic mesophase for [Ag4(L4-C16)6]­[BF4]4 is observed because of the presence of a three-dimensional ion-transporting channel. Doping a small amount of AgBF4 enhances the ionic conduction dramatically, presumably via promotion of the migration of AgI ions in the channels.