Properties and Synthetic Performances of Phenylamino Cyanoarenes under One-Photon Excitation Manifolds

Abstract

The synthesis of a set of new organic photocatalysts (PCs) with a donor-acceptor carbazolyl dicyanobenzene structure is reported. The PCs developed have fine-tailored redox potentials from -1.62 V (PC•+/PC*) to 1.36 V (PC*/PC•-) and have been accessed through a straightforward two-step synthesis. The potential of these PCs was demonstrated in synthetically relevant photoreactions with mechanistic opposite thermodynamic requirements, previously reported only in the presence of precious Ir-based PCs. Interestingly, the herein reported purely organic PCs outperformed the well-established 4CzIPN organic dye under both types of reaction manifolds.

The Rational Design of Reducing Organophotoredox Catalysts Unlocks Proton-Coupled Electron-Transfer and Atom Transfer Radical Polymerization Mechanisms

“…This MO distribution suggests access to a CT excited state while allowing the exploitation of the free amino group. Based on previous precedents, − , the CF 3 and CN groups were selected to evaluate the impact of an increased electron-withdrawing (EW) character of the exocyclic aryl ring on the MOs, and later on the overall photoredox properties of the molecules.…”

“…In this context, the current development of photocatalysis has set previously inaccessible mechanistic vistas, while allowing operation under mild and sustainable reaction conditions . In particular, the identification and use of simple and purely organic molecules as photocatalysts (PCs) has become a major goal in the chemical community . Organic PCs present clear advantages with respect to their metal counterparts (e.g., Ru- or Ir-complexes), including (i) their higher accessibility and sustainability, (ii) their overall lower price, and (iii) a higher tunability of their scaffolds, which enables (iv) a more direct assessment of the structure–property relationships .…”

“…In particular, the identification and use of simple and purely organic molecules as photocatalysts (PCs) has become a major goal in the chemical community . Organic PCs present clear advantages with respect to their metal counterparts (e.g., Ru- or Ir-complexes), including (i) their higher accessibility and sustainability, (ii) their overall lower price, and (iii) a higher tunability of their scaffolds, which enables (iv) a more direct assessment of the structure–property relationships . Likewise the metal-to-ligand charge transfer (MLCT) in metal complexes, organic PCs can access a charge transfer (CT) excited state.…”

“…The new electron distribution grants access to more stable excited states that have an extended lifetime (from ns to μs) as well as more balanced redox potentials . In this context, highly reducing organic PCs play a crucial role. , These molecules are highly efficient for the activation of alkyl and aryl halides, ketones, and aldehydes, as well as for the generation of polymers under mild metal-free conditions, thus overcoming metal-contamination issues. , …”

Organophotocatalytic Mechanisms: Simplicity or Naïvety? Diverting Reactive Pathways by Modifications of Catalyst Structure, Redox States and Substrate Preassemblies

“…Inspired by the stability and redox properties of 3CzEPAIPN , Vega‐Peñaloza, Dell'Amico and co‐workers synthesized analogues of 3CzEPAIPN , with different substituents at the carbazole moieties. They discovered that the electron‐rich derivative 3[(MeO) 2 Cz]EPAIPN has significant absorbance reaching up to 496 nm and bears a redox window ( E 1/2 ( PC ⋅ + / PC *)=−1.49 V; E 1/2 ( PC */ PC ⋅ − )=+0.98 V) which can effect photoreductions under one photon conditions (not shown) [82] …”