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.