No abstract

Over the past decade, chemists have embraced visible-light photoredox catalysis due to its remarkable ability to activate small molecules. Broadly, these methods employ metal complexes or organic dyes to convert visible light into chemical energy. Unfortunately, the excitation of widely utilized Ru and Ir chromophores is energetically wasteful as ∼25% of light energy is lost thermally before being quenched productively. Hence, photoredox methodologies require high-energy, intense light to accommodate said catalytic inefficiency. Herein, we report photocatalysts which cleanly convert near-infrared (NIR) and deep red (DR) light into chemical energy with minimal energetic waste. We leverage the strong spin–orbit coupling (SOC) of Os(II) photosensitizers to directly access the excited triplet state (T 1 ) with NIR or DR irradiation from the ground state singlet (S 0 ). Through strategic catalyst design, we access a wide range of photoredox, photopolymerization, and metallaphotoredox reactions which usually require 15–50% higher excitation energy. Finally, we demonstrate superior light penetration and scalability of NIR photoredox catalysis through a mole-scale arene trifluoromethylation in a batch reactor.

Aryl amination is an essential transformation for medicinal, process, and materials chemistry. In addition to classic Buchwald−Hartwig amination conditions, blue-light-driven metallaphotoredox catalysis has emerged as a valuable tool for C−N cross-coupling. However, blue light suffers from low penetration through reaction media, limiting its scalability for industrial purposes. In addition, blue light enhances unwanted side-product formation in metallaphotoredox catalysis, namely hydrodehalogenation. Low-energy light, such as deep red (DR) or near-infrared (NIR), offers a solution to this problem as it can provide enhanced penetration through reaction media as compared to higher-energy wavelengths. Herein, we show that lowenergy light can also enhance the desired reactivity in metallaphotoredox catalysis by suppressing unwanted hydrodehalogenation. We hypothesize that the reduced side product is formed by direct photolysis of the aryl−nickel bond by the high-energy light, leading to the generation of aryl radicals. Using deep-red or near-infrared light and an osmium photocatalyst, we demonstrate an enhanced scope of (hetero)aryl bromides and amine-based nucleophiles with minimal formation of hydrodehalogenation byproducts.

Recent studies demonstrated that with proper selection of chemically compatible constituents the open-circuit voltage (V oc ) of ternary-blend solar cells can be tuned across the composition window of the active layer. In this study, we probed the limit of the offset between the lowest unoccupied molecular orbital (LUMO) energy levels of the two acceptors in ternary blends containing one donor and two acceptors. We demonstrate, for the first time, that ternary-blend active layers with two acceptors having an energy-level difference between their LUMO levels exceeding 0.4 eV can still result in solar cells exhibiting compositiondependent open-circuit voltage (V oc ). Our results suggest strong electronic interactions between the acceptors, with the electron wave function delocalized over multiple molecules. These findings have broadened the library of possible candidates for active layers of ternary-blend solar cells with tunable V oc and established guidelines for the design of next-generation materials for efficient performance of such devices.

Using light to drive a chemical transformation introduces challenges for ensuring the robust transferability of photochemical reactions across different platforms and scales. We demonstrate a modeling tool to predict the performance of a photochemical reaction as a function of the reactor geometry, concentration of the photoactive species, irradiance of the light source, and residence time. High-throughput experimentation is utilized to optimize reaction conditions and to determine kinetic parameters and quantum yield. Optical characterization of the photoactive reaction species and the reactor is performed to determine the photon absorption rate. The experimental data is combined with computational modeling to predict photochemical conversion for different vial or flow reactors across multiple scales for a [2 + 2] photocycloaddition reaction and a photoredoxmediated decarboxylative intramolecular arene alkylation reaction. The method developed in this work facilitates the transferability of the photochemical processes between different photoreactors without the need for an intensive experimental optimization for each and enables a robust and efficient scale-up.