Bridged Azobenzene Enables Dynamic Control of Through-Space Charge Transfer for Photochemical Conversion.

Through-space charge transfer (TSCT) has become a thriving strategy of modulating photogenerated charges in organic photoresponsive molecular systems for potential applications in luminescence, optoelectronics, and photochemical conversion. Yet fixed configuration between electron donor (D) and acceptor (A) is disadvantageous to mitigate charge recombination undermining their performances. By carrying out first-principle simulations, we proposed a protocol enabling dynamic control of TSCT within a D-A system by use of a bridged azobenzene (BAB), whose configuration is self-adaptive upon photoexcitation. While the Z-isomer of BAB facilitates π-π stacking of D-A pair with designated frontier orbital alignment to ensure TSCT, the E-isomer of BAB breaks that stacking and restrains charge recombination. Further, as a CO2 molecule is weakly bound to the anionic acceptor, the former goes bent as a result of charge transfer from the latter, suggesting a path for photodriven CO2 reduction aided by such a donor-switch-acceptor system. Our proof-of-concept study shows the potential of using specific photoswitch to adaptively steer spatial electron transfer within stacked π systems toward photochemical conversion.