Supramolecular Modulation of Photoinduced Charge Transfer: Tuning Between Tunneling and Incoherent Hopping

Photoinduced charge transfer (CT) underpins photosynthesis and solar energy conversion technologies. However, achieving comprehensive control over CT in traditional covalent donor-bridge-acceptor (D-B-A) systems remains challenging, hindered by tedious organic synthesis and limited tunability. In this investigation, we harness molecular recognition to regulate photoinduced CT-including charge separation and recombination-leveraging its facile preparation and dynamic reversibility. By integrating guest molecules with a wide range of frontier orbital energies into a rigid cyclophane host (DAPPTTzBox⁴⁺), which features directional photoinduced intramolecular CT through cofacially stacked chromophores, we achieve comprehensive modulation of CT within well-defined supramolecular complexes. This modulation spans mechanisms from tunneling to incoherent hopping. Notably, molecular recognition accelerates charge separation in DAPPTTzBox⁴⁺ by 5.9- to 230-fold, shifting from single-step superexchange to multistep incoherent charge shift, while charge recombination rates are decreased (from 1.3‑ to 2.8‑fold) in superexchange systems. Additionally, guest-induced charge trapping was also successfully demonstrated. This research exemplifies a fresh strategy for manipulating CT dynamics via noncovalent interactions, opening new avenues for the design of advanced artificial light-harvesting materials.