Supramolecular modulation of π-extended pyridinium photosensitizers for enhanced dual reactive oxygen species photocatalysis

Abstract

The efficient and simultaneous generation of multiple reactive oxygen species (ROS) by a single photosensitizer under mild and environmentally benign conditions remains challenging. Herein, we present a supramolecular host-guest approach to construct a high-performance dual-ROS-generating photocatalytic system based on a π-extended pyridinium photosensitizer. The phenyl-substituted photosensitizer CTPy intrinsically produces both singlet oxygen (1O2) and superoxide anion radicals (O2•−), whereas the methyl analogue CNPy lacks such dual activity even after complexation with cucurbit[7]uril (CB[7]) or cucurbit[8]uril (CB[8]). Encapsulation of CTPy by CB[7] or CB[8] yields discrete assemblies (CTPy-CB[7] and 2CTPy-CB[8]) that substantially enhance dual ROS generation, with the efficiency trend CTPy-CB[7] > 2CTPy-CB[8] > CTPy. Enabled by this supramolecularly amplified photosensitization, we realized a metal-free, visible-light-induced cross-dehydrogenative coupling between P(O)H compounds and thiols in water under air, employing O2 from air as the terminal oxidant. These results highlight supramolecular confinement as a general strategy to modulate excited-state behavior and enable sustainable aqueous photoredox transformations.