Jstevens

Effects of Naphthyl Connectivity on the Photophysics of Organic Charge-Transfer PCs

Abstract: Modular chromophoric systems with minimal electronic coupling between donor and acceptor moieties are well suited for establishing predictive relationships between molecular structure and excited-state properties. Here, we investigate the impact of naphthyl-based connectivity on the photophysics of phenoxazine-derived orthogonal donor–acceptor complexes. While compounds in this class are themselves interesting as potent organic photocatalysts useful…

Phenothiazines, Dihydrophenazines, and Phenoxazines: Sustainable Photoredox Catalysts

Abstract: The application of photoredox catalysis to atomtransfer radical polymerization (ATRP) has resulted in the development of strongly reducing organic photoredox catalysts (PCs) that are some of the most reducing catalysts known. The objectives of this review are to highlight these PCs with regard to their development and applications in polymer and organic synthesis, as…

Photoinduced Organocatalyzed Atom Transfer Radical Polymerization Using Low ppm Catalyst Loading

Abstract: Photoinduced organocatalyzed atom-transfer radical polymerization (O-ATRP) is a controlled radical polymerization methodology that can be mediated by organic photoredox catalysts under the influence of light. However, typical O-ATRP systems require relatively high catalyst loadings (1000 ppm) to achieve control over the polymerization. Here, new core-extended diaryl dihydrophenazine photoredox catalysts were developed for O-ATRP and…

Visible-Light-Driven Conversion of CO2 to CH4 with an Organic Sensitizer and an Iron Porphyrin

Abstract: Using a phenoxazine-based organic photosensitizer and an iron porphyrin molecular catalyst, we demonstrated photochemical reduction of CO2 to CO and CH4 with turnover numbers (TONs) of 149 and 29, respectively, under visible-light irradiation (λ > 435 nm) with a tertiary amine as sacrificial electron donor. This work is the first example of a molecular…

Visible‐Light‐Mediated Liberation and In Situ Conversion of Fluorophosgene

Abstract: The first example for the photocatalytic generation of a highly electrophilic intermediate that is not based on radical reactivity is reported. The single‐electron reduction of bench‐stable and commercially available 4‐(trifluoromethoxy)benzonitrile by an organic photosensitizer leads to its fragmentation into fluorophosgene and benzonitrile. The in situ generated fluorophosgene was used for the preparation of carbonates,…

What happens in the dark? Assessing the temporal control of photo controlled radical polymerizations

Abstract: A signature of photo‐mediated controlled polymerizations is the ability to modulate the rate of polymerization by turning the light source ‘on’ and ‘off.’ However, in many reported systems, growth can be reproducibly observed during dark periods. In this study, emerging photo‐mediated controlled radical polymerizations are evaluated with in situ 1H NMR monitoring to assess…

Organocatalyzed Atom Transfer Radical Polymerization Catalyzed by N-Aryl Phenoxazines under Air

Abstract: Organocatalyzed atom transfer radical polymerization (O-ATRP) was performed under air using core modified N-aryl phenoxazines as photoredox catalysts (PCs) to synthesize poly(methyl methacrylate) in a controlled fashion with initiator efficiency (I* = Mn,theo/Mn × 100) ranging from 84 to 99% and dispersity being ∼1.2–1.3. Reduction of the reaction vial headspace was key for enabling…