Synthetic Photoelectrochemistry

Abstract

Photoredox catalysis (PRC) and synthetic organic electrochemistry (SOE) are often considered competing technologies in organic synthesis. Their fusion has been largely overlooked. We review state‐of‐the‐art synthetic organic photoelectrochemistry, grouping examples into three categories: 1) electrochemically mediated photoredox catalysis (e‐PRC), 2) decoupled photoelectrochemistry (dPEC), and 3) interfacial photoelectrochemistry (iPEC). Such synergies prove beneficial not only for synthetic “greenness” and chemical selectivity, but also in the accumulation of energy for accessing super‐oxidizing or ‐reducing single electron transfer (SET) agents. Opportunities and challenges in this emerging and exciting field are discussed.

Making electrochemistry easily accessible to the synthetic chemist

“…28,30,[32][33][34] This concept has also been applied to photocatalysts. 121 Morrill and co-workers have developed the electrocatalysed deconstructive chlorination of cycloalkanols (Scheme 6). 122 The manganese(II) catalyst is activated by addition of a chloride ligand before it is electrochemically oxidised to manganese(III).…”

Photo-triggered hydrogen atom transfer from an iridium hydride complex to unactivated olefins

“…Consequently, the vast majority of current photochemical studies, including most of the work by the photoredox community, 8 still operate on the basis of PET. Even though increasingly thermodynamically challenging PET reactions have been accomplished lately, [9][10][11][12][13][14][15][16][17][18] sometimes in combination with an applied electrochemical potential, [19][20][21] such reactions are limited by the redox properties of the photosensitizer and the substrates. To overcome thermodynamic limitations imposed by PET, protoncoupled electron transfer (PCET) 22 has been exploited successfully in photoredox catalysis for substrates with sufficiently polar functional groups that can form hydrogen bonds.…”

Aryl dechlorination and defluorination with an organic super-photoreductant

“…To circumvent the abovementioned challenges associated with biphotonic excitation, the concept of electro-photocatalysis 34 has been revitalized in order to achieve very high reducing power upon monophotonic excitation of electrochemically generated radical anions. 35,36 Specific examples include dicyanoanthracene radical anion providing a potential of −3.2 V vs. SCE in its excited-state, 37 and an excited naphthalene monoimide radical anion with a potential of −3.3 V vs. SCE. 38 These concepts are elegant, but many radical anions have very short excited-state lifetimes, 39 and catalyst-substrate preorganization may be needed because bimolecular diffusion is slow compared to excited-state deactivation.…”