Metal-Organic Framework Supported Copper Photoredox Catalysts for Iminyl Radical-Mediated Reactions.

Visible-light copper photocatalysis has recently emerged as a viable technology for building sustainable synthetic processes. To broaden the applications of phosphine-ligated copper(I) complexes, we describe herein an effective metal-organic framework (MOF)-supported copper(I) photocatalyst for multiple iminyl radical-mediated reactions. Due to site isolation, the heterogenized copper photosensitizer has a significantly higher catalytic activity than its homogeneous counterpart. Using a hydroxamic acid linker to immobilize copper species on MOF supports affords the heterogeneous catalysts with high recyclability. The post-synthetic modification sequence on MOF surfaces allows for the preparation of previously unavailable monomeric copper species. Our findings highlight the potential of using MOF-based heterogeneous catalytic systems to address fundamental challenges in the development of synthetic methodologies and mechanistic investigations of transition-metal photoredox catalysis.

Self-Assembly of Molecular Trefoil Knots Featuring Pentadecanuclear Homoleptic AuI -, AuI /AgI -, or AuI /CuI -Alkynyl Coordination.

Metal-free and metal-containing molecular trefoil knots are fascinating ensembles that are usually covalently assembled, the latter requiring the rational design of di- or multidentate/multipodal ligands as connectors. In this work, we describe the self-assembly of pentadecanuclear AuI trefoil knots [Au15 (C≡CR)15 ] from monoalkynes HC≡CR (R=9,9-X2 -fluorenyl with X=nBu, n-hexyl) and [AuI (THT)Cl]. Hetero-bimetallic counterparts [Au9 M6 (C≡CR)15 ] (M=Cu/Ag) were self-assembled by reactions of [Au15 (C≡CR)15 ] with [Cu(MeCN)4 ]+ /AgNO3 and HC≡CR. The type of pentadecanuclear trefoil knots described herein is characterized by X-ray crystallography, 2D NMR and HR-ESI-MS. [Au9 Cu6 (C≡CR)15 ] is relatively stable in hexane; its excited state properties were investigated. DFT calculations revealed that non-covalent metal-metal and metal-ligand interactions, together with longer alkyl chain-strengthened inter-ligand dispersion interactions, govern the stability of the trefoil knot structures.

Photophysical and Electroluminescent Properties of PtAg2 Acetylide Complexes Supported with meso- and rac-Tetraphosphine.

1,2-Bis[[(diphenylphosphino)methyl](phenyl)phosphino]ethane (dpmppe) was prepared as a new tetraphosphine, and the corresponding rac and meso stereoisomers were successfully separated in view of their solubility difference in acetone. The substitution of PPh3 into Pt(PPh3)2(C≡CR)2 (R = aryl) with rac- or meso-dpmppe gives Pt(rac-dpmppe)(C≡CR)2 or Pt(meso-dpmppe)(C≡CR)2, respectively. Using Pt(rac-dpmppe)(C≡CR)2 or Pt(meso-dpmppe)(C≡CR)2 as a precursor, PtAg2 heterotrinuclear cluster complexes were synthesized and characterized by X-ray crystallography. Depending on the conformations of tetraphosphine, the structures of PtAg2 complexes supported with rac- and meso-dpmppe are quite different. The higher molecular rigidity of rac-dpmppe-supported PtAg2 complexes results in stronger phosphorescent emission than that of PtAg2 species with meso-dpmppe. The high phosphorescent quantum yields (as high as 90.5%) in doping films warrant these PtAg2 complexes as excellent phosphorescent dopants in organic light-emitting diodes (OLEDs). The peak current and external quantum efficiencies in solution-processed OLEDs are 61.0 cd A-1 and 18.1%, respectively. Electroluminescence was elaborately modulated by modifying the substituent in aromatic acetylide and the conformations in tetraphosphine so as to achieve cyan, green, green-yellow, yellow, and orange-red emission.