Effects of Lewis Acids on Photoredox Catalysis

Abstract

The reactivityo fo rganic photoredox catalysts in oxidation reactions is enhanced by the addition of Lewis acids, which bind to the catalyst to increasei ts oxidizing ability.R edox-inactivem etal ions, such as Sc 3 + ,a lso act as Lewis acids and can bind to flavins to increaset heir oneelectron reduction potentials and photocatalytic stability. The Sc 3 + ion can bind to acridine and pyrene to enhance their photoredox catalytic activity in the oxidation of substrates by dioxygen. The binding of Lewis acids to radical anions enhances their overall photocatalytic activity by prohibitingab ack electron transfer from the radicala nions of substrates to the oxidized photocatalysts.T he photocatalytic asymmetrico xidationo ft erminal olefins by using water as the oxygen source with am ononuclear nonheme chiral manganese complex has been made possible by the addition of acetic acid, which is essential to afford the products with high enantioselectivity.[a] Prof.Scheme3.Quantitative measureo ft he Lewis acidity (DE)a nd ionic radius of redox-inactive metal ions.

Non-covalent polyhedral oligomeric silsesquioxane-polyoxometalates as inorganic–organic–inorganic hybrid materials for visible-light photocatalytic splitting of water

“…Subsequently, the luminescence intensity of POM(MoV)-POSS was lower than those of other materials, thus revealing the presence of two different metal sites; this further improved the electron-hole pair separation by inducing electron deficient behavior, which enhanced the photocatalytic hydrogen production activity. 44 To further authenticate photoelectron generation and electron-hole pair separation of POM-POSS hybrid materials, a photocurrent experiment was performed. As clearly seen from Fig.…”

Advanced Synthesis Using Photocatalysis Involved Dual Catalytic System

“…Alternatively, the strong binding of Lewis acids to radical counterions inhibits the reverse electron transfer from the radical ions of the substrate to the oxidized photocatalyst, thereby improving the overall photocatalytic activity. [12] The earliest report of the remarkable enhancement of photoredox reaction by Lewis acid metal ions is the photocatalytic oxidation of benzyl alcohol derivatives by dioxygen using flavin and deazaflavin as organic photoredox catalysts. [13] In 1989, Lewis and Barancyk reported that the use of Lewis acids as catalysts enabled the intermolecular [2 + 2] photocycloaddition of coumarins and different olefins.…”

Photoredox Dual Catalysis: A Fertile Playground for the Discovery of New Reactivities

“…Lewis [33] and Brønsted acid catalysis in combination with photoredox catalysis has found widespread use due to the ability of such activation modes to impact the redox properties and reactivities of organic substrates. Brønsted acids can dramatically accelerate photo‐reductive processes, enabling proton‐coupled electron transfer (PCET) pathways [34] .…”