Supramolecular Engineering of Discrete Pt(II)···Pt(II) Interactions for Visible-Light Photocatalysis

Visible-light photosensitizers have emerged as a sustainable and environmentally friendly medium for organic transformation. Herein, we have developed a supramolecular strategy for manipulating visible-light photosensitization and photocatalytic efficiencies. With the elaborate manipulation of aggregated Pt(II)···Pt(II) interactions, the discrete tetranuclear Pt complexes not only show high binding affinity ( K a ∼ 10 6 M –1 ) but also feature bathochromic-shifted metal–metal-to-ligand charge transfer transitions. Both factors are crucial for their 1 O 2 generation capability upon low-energy visible-light irradiation (λ ≥ 590 nm). More interestingly, when a terpyridine moiety is embedded in the structure of a supramolecular photosensitizer, breakup of tetranuclear Pt(II)···Pt(II) complexation can be realized upon addition of Zn(OTf) 2 . As a consequence, photo-oxidation of a secondary amine to the corresponding imine can be deactivated and reactivated, via the sequential addition of Zn(OTf) 2 and unsubstituted terpyridine as the competitive ligand. Hence, the current study proves that intelligent visible-light photocatalysts can be achieved via rational supramolecular design.