Cuprous Cluster-Based Coordination Sheets as Photocatalytic Regulators to Activate Oxygen, Benzoquinone, and Thianthrenium Salts

Cuprous
clusters are well known for their important fluorescent
properties and tunable redox behavior, but the coordinated protecting
groups restrict their application in photocatalysis, in particular,
the inner-sphere activation of substrates. By modifying fluorescent
cuprous clusters with terminal iodides into two-dimensional coordination
sheets, we report a photocatalytic regulator to synergistically combine
electron transfer and energy transfer for the oxidative coupling of
benzoquinone and terminal alkynes. Under visible light irradiation,
the well-modified excited state of the cuprous clusters in the coordination
sheets reduces benzoquinones to generate aoxy radicals through electron
transfer and activates oxygen through energy transfer. The aoxy radicals
interact with copper-coordinated phenylacetylene to form an active
intermediate, which is further oxidized by the in situ formed active oxygen species and aryl ketones are obtained. The
warranted potential of the excited coordination sheets enables the
reductive activation of thianthrenium salts as radical precursors,
facilitating radical capture and further C–N coupling via an inner-sphere activation mechanism. The new catalytic
approach optimizes the redox properties and excited-state lifetime,
shortens the electron transfer steps, and promotes the potential collision
of a low concentration of active species in tandem catalytic cycles,
thus paving a new way to develop ecologically benign, cost-effective,
multipurpose, and flexible catalytic systems.