Site Isolation in Metal–Organic Layers Enhances Photoredox Gold Catalysis

Abstract

Herein, we report the synthesis of a metal–organic layer, Hf–Ru–Au, containing Ru­(bipyridine)3 2+-type photosensitizers and (phosphine)-AuCl catalysts for photoredox Au-catalyzed cross-coupling of allenoates, alkenes, or alkynes with aryldiazonium salts to afford furanone, tetrahydrofuran, or aryl alkyne derivatives, respectively. Site isolation of (phosphine)-AuCl complexes in Hf–Ru–Au prevents Au catalyst deactivation via ligand redistribution, Au­(I) disproportionation, and aryl-phosphine reductive elimination, while the proximity between the Ru photosensitizers and Au catalysts enhances catalytic efficiency, with 14–200 times higher activity over those of the homogeneous controls in the cross-coupling reactions.

Polypyridyl Ru(ii) or cyclometalated Ir(iii) functionalized architectures for photocatalysis

“…Ru(bpy) 2 (N^N) photosensitizer and Au + catalysts worked synergistically for the cross-coupling of allenoates, alkenes, or alkynes. 271…”

Molecular Engineering of Metal–Organic Layers for Sustainable Tandem and Synergistic Photocatalysis

“…MOL catalysts also exhibit enhanced stability over their homogeneous counterparts due to active site isolation, which shuts down common multimolecular catalyst deactivation pathways. 28,29 The ease of recovery and the extended catalyst lifetime enable the efficient reuse of MOL catalysts to reduce the consumption of precious resources, the generation of hazardous waste materials, and the economic costs. Despite their great potential for sustainable catalysis, the difficulty in MOL synthesis and characterization presents a significant bottleneck for the further development of MOL catalysts.…”

“…This strategy has been successfully used to design MOLs for photoredox dual catalysis. MOLs built from photosensitizing bridging ligands were modified with nickel, cobalt, and gold catalysts or Lewis acids for various photocatalytic transformations. ,− Installation of two catalytic sites in proximity in MOLs facilitates electron and mass transfer to significantly enhance their catalytic performance.…”

“…Although highly dispersible in common organic solvents, MOL catalysts can be readily recovered from reaction mixtures by simple centrifugation or filtration. MOL catalysts also exhibit enhanced stability over their homogeneous counterparts due to active site isolation, which shuts down common multimolecular catalyst deactivation pathways. , The ease of recovery and the extended catalyst lifetime enable the efficient reuse of MOL catalysts to reduce the consumption of precious resources, the generation of hazardous waste materials, and the economic costs …”

Sequential Modifications of Metal–Organic Layer Nodes for Highly Efficient Photocatalyzed Hydrogen Atom Transfer

“…Recently, Duan and co-workers encapsulated anthraquinone into MOFs to obtain a site-isolated HAT photocatalyst, which accelerates reverse HAT and prevents catalyst decomposition via dimerization . However, the three-dimensional structures of MOFs cannot readily accommodate hierarchical installation of multiple active sites. − We have developed two-dimensional metal–organic layers (MOLs) via proximal installation of multiple functionalities to promote synergistic and tandem photoredox catalysis. − We hypothesized that a bifunctional HAT photocatalyst could be synthesized by installing Lewis acids and HAT photocatalysts through sequential modifications of secondary building units (SBUs) or nodes (Figure b) . We further posited that the proximally placed Lewis acids and HAT catalysts could synergistically activate olefinic substrates for the addition of HAT-generated radicals to accelerate reaction rates and improve selectivity for hydrofunctionalization products.…”