Ligand-to-Metal Charge Transfer of Ag(II) CF2X Carboxylates: Quantum Yield and Electrophotocatalytic Arene Fluoroalkylation Tuned by X.

Abstract

Incorporation of CF2X groups beyond CF3 into arene scaffolds is underdeveloped despite these groups' utility as halogen-bond donors and as precursors to bioisosteres. Herein, we report the synthesis, characterization, and comparative photochemistry of a suite of [Ag(II)(bpy)2O2CCF2X]+ and Ag(II)(bpy)(O2CCF2X)2 (bpy = 2,2´-bipyridine, X = F, CF3, Cl, Br, H, CH3) carboxylate complexes. We find a dramatic effect of the X substituent on the efficiency of generating CF2X radicals by ligand-to-metal charge transfer (LMCT), with Ag(II) photoreduction rates varying by over an order of magnitude and quantum yields spanning over 20%. We provide insight into how electronic and structural perturbations of the Ag(II)-O2CCF2X core are manifested in the LMCT quantum efficiency. With this information in hand, Ag(II)-mediated electrophotocatalytic CF2X functionalization is carried out on a range of (hetero)arenes. This work expands the nascent field of Ag(II)-based photocatalysis by allowing for (hetero)aryl-CF2X functionalization directly from unactivated fluoroalkyl carboxylate precursors.