-Terphenylene Viologens with Through-Space Conjugation for Enhanced Photocatalytic Oxidative Coupling and Hydrogen Evolution.

A series of novel terphenylene viologen derivatives (TPV) with through-space conjugation (TSC) via the combination of terphenylene skeletons with viologen structure is reported. Their optoelectronic properties can be adjusted by -arylation or -alkylation reactions. Compared with other viologen derivatives, TPV not only exhibits strong photoluminescence but also retards the charge recombination process and stabilizes the diradical state without forming a quinoid structure due to the special TSC effect. Based on their special redox characteristics, TPV was applied to the photocatalytic oxidative coupling of benzylamine with 96% yield. In addition, TA-TPV (tethered with -toluic acid)-modified g-CN was used for visible-light-driven hydrogen production for the first time, exceeding 15 times the rate over unmodified g-CN.