Photoredox catalysis is important in modern organic chemistry and the development of new synthetic methods. Mechanistic insights, particularly with photoredox chain reactions, are underdeveloped. This study combines quantum yield (QY) measurements, transient absorption spectroscopy (TAS), and electrochemical analysis to rigorously characterize the mechanism and rate constants of a ruthenium-catalyzed photoredox chain [4 + 2] cyclization between trans-anethole and isoprene. TAS and steady-state photochemical measurements (QY studies) reveal the role of oxygen in chain propagation as a secondary electron acceptor. The key kinetic competition between chain propagation and termination is identified by TAS and explored with kinetic modeling.

Photoredox catalysis has emerged as a transformative strategy in synthetic chemistry, enabling a wide variety of valuable chemical reactions through generation of highly reactive radical ion intermedi...

The reduction potentials of electronically excited states are crucial input values for photoredox reaction design. Since they are not directly measurable, they are typically estimated from the corresp...

Nearly all photochemical transformations known to date follow Kasha’s rule, implying that reactions occur only from the lowest electronically excited state of a given spin multiplicity due to the fast...

Many important synthetic-oriented works have proposed excited organic radicals as photoactive species, yet mechanistic studies raised doubts about whether they can truly function as photocatalysts. This skepticism originates from the formation of (photo)redox-active degradation products and the picosecond decay of electronically excited radicals, which is considered too short for diffusion-based photoinduced electron transfer reactions. From this perspective, we analyze important synthetic transformations where organic radicals have been proposed as photocatalysts, comparing their theoretical maximum excited state potentials with the potentials required for the observed photocatalytic reactivity. We summarize mechanistic studies of structurally similar photocatalysts indicating different reaction pathways for some catalytic systems, addressing cases where the proposed radical photocatalysts exceed their theoretical maximum reactivity. Additionally, we perform a kinetic analysis to explain the photoinduced electron transfer observed in excited radicals on subpicosecond time scales. We further rationalize the potential anti-Kasha reactivity from higher excited states with femtosecond lifetimes, highlighting how future photocatalysis advancements could unlock new photochemical pathways.

An unexpectedly long excited-state lifetime makes an Earth-abundant cobalt complex an effective photoredox catalyst.

Surface chemistry is central to the design of colloidal quantum dots (QDs) for photoredox catalysis, where charge transfer, access to active sites, and colloidal stability must be balanced. Using CsPb...

Photoredox catalysis driven by visible light has improved chemical synthesis by enabling milder reaction conditions and unlocking distinct reaction mechanisms. Despite the transformative impact, visib...

A dual photoredox/hydrogen atom transfer (HAT) strategy for the radical alkoxycarbonylation of allenes is described. Alkoxycarbonyl radicals, generated by photoredox-catalyzed decarboxylation of alkyl...

Transition-metal complexes featuring metal-centered excited states have recently emerged as mechanistically distinct platforms for selective photochemistry, including photoredox catalysis. Among these...

We have developed the N-heterocyclic carbene/organic photoredox-cocatalyzed acyl azolation of styrenes using acyl azoles. The cooperative action of organic photoredox catalysis and NHC catalysis enabl...

A general strategy has been developed for predictable and robust vinyl halide cross-coupling reactions. This approach demonstrates broad applicability across seven distinct bond-forming transformatio...

Organic photoredox catalysts show promise for fluorinated pollutants