In a mixed-valence polyoxometalate, electrons are usually delocalized within the cluster anion because of low level of inter-cluster interaction. Herein, we report the structure and electrical properties of a single crystal in which mixed-valence polyoxometalates were electrically wired by cationic -molecules of tetrathiafulvalene substituted with pyridinium. Electron-transport characteristics are suggested to represent electron hopping through strong interactions between cluster and cationic pi-molecules.