Oriented Electric Field-Driven Cis-Azobenzene Selective Diborylation Reaction at the Single-Molecule Level.

The development of catalysts with a built-in electric field to catalyze and control complex chemical reactions under mild conditions with exceptional stereo and regioselectivity remains a key objective in synthetic chemistry. In this work, we demonstrate a novel approach in which the intrinsic electric field within a break junction nanocavity triggers and probes a substrate-selective, multistep cis-azobenzene diborylation reaction in the dark at the single-molecule level under ambient conditions. Our results combine the key aspects of electric field catalysis and substrate recognition to drive reactions in a nanoscale confined environment. The study further demonstrates how the reactivity landscape for the "N═N" bond functionalization and borylation reactions can be tuned by an oriented external electrical field present within a nanometallic junction, opening a new avenue in borylation chemistry. Furthermore, theoretical studies corroborate the experimental finding by revealing how the trans-cis-azobenzene isomerization energy landscape can be reshaped in the presence of an electric field to facilitate a cis-azobenzene selective diborylation reaction without the aid of a metal catalyst or external light irradiation.