Accelerated Bidirectional Photoinduced Electron Transfer in A Photo-chromic Polyoxoniobate Enabled by Excited Bridge

Abstract The bridge connecting the electron donor and acceptor is crucial for electron transfer, however, the impact of the excited bridge on this process remains unclear. Here, we present a proof-of-concept model using an f-type bridge in an electron transfer photochromic poly-oxoniobate. We discovered that the excited bridge significantly accelerates electron transfer, resulting in a 3.3-fold increase in the col-oring rate. Colored samples exhibit accelerated bleaching when excited by light, marking the first instance of light-assisted acceleration of reverse electron transfer, which was previously constrained by thermal mode. The light-assisted bleaching rate is approximately 494 times faster than the traditional thermal mode at room temperature, leading to a significant reduction in the half-life from 91.58 min to 11.13 s. The study identifies that the primary cause of the increased electron transfer rate is the significant enhancement in electronic coupling between the initial and colored states by the excited bridge. This intriguing photochromic behavior not only opens up new applications for multi-factor anti-counterfeiting but also initiates research into the electron transfer chemistry of excited bridges.