Host-stabilized charge transfer (HSCT) has been widely utilized in macrocycle-derived supramolecular assemblies and architectures. However, there has been less research attention focused on the direct fabrication of pure organic photocatalysts using HSCT. Herein, four viologen derivatives (m-PV2+, m-BPV2+, d-PV2+, and d-BPV2+) with different electron donor-acceptor (D-A) structures were synthesized. Their host-guest complexes with cucurbit[8]uril (Q[8]) in an aqueous solution could be switched using the substituted electron donor moieties, in which the host-guest complexes of m-BPV2+@Q[8] andd-BPV2+@Q[8] exhibited HSCT interactions. Control experiments revealed that the d-BPV2+@Q[8] complex had the strongest ability to sensitize singlet oxygen (1O2). This was ascribed to the increased π-conjugation of d-BPV2+@Q[8], which led to more effective HSCT upon encapsulation by the Q[8] host. Consequently, the d-BPV2+@Q[8] complex could be easily employed as a heterogeneous photocatalyst for the photooxidation reaction of thioether com-pounds with high selectivity. In particular, d-BPV2+@Q[8] was successfully applied to the synthesis of sulfoxide drugs, such as the con-version of inexpensive Iberverin ($7.0 per gram) to the expensive bioactive inhibitor Iberin ($19500.0 per gram) in high yield (94%).
Keywords: Heterogeneous photocatalyst; Host-stabilized charge transfer; Organic transformations; Singlet oxygen; supramolecular self-assembly.
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