Constructing Conformation-Restricted Terpyridine Complexes by Manipulating the Flexible Chain Length for...

Improving the photocatalytic performance via precisely tailoring molecular conformation remains elusive. Herein, we report a novel strategy for constructing conformation-restricted complexes by incorporating flexible chains. Using this approach, we synthesized three terpyridine-based charge-transfer (CT) complexes (S-12, S-13, and S-14) whose conformations were tuned by manipulating the flexible chain length. These conformation-restricted complexes were fully characterized and showed markedly different electronic structures and excited-state properties. Among them, S-12, with the shortest chains, adopts the most restricted conformation, which stabilizes the CT excited state and leads to the longest excited-state lifetime. From S-14 to S-12, the photocatalytic performance demonstrates a progressive enhancement, which can be attributed to enhanced exciton dissociation through stabilization of the CT excited state by more restricted conformations. This is a worthwhile example of improving photocatalytic performance through manipulation of restricted molecular conformation. Remarkably, complex S-12 achieves an outstanding H₂O₂ evolution rate of 7905 μmol g^-1 h^-1 in pure H₂O under air, surpassing most reported organic photocatalytic systems.