Cofactor‐Free,Direct Photoactivation of Enoate Reductases for the Asymmetric Reduction of C=C Bonds

Enoate reductases from the family of old yellow enzymes (OYEs) can catalyze stereoselective trans ‐hydrogenation of activated C=C bonds. Their application is limited by the necessity for a continuous supply of redox equivalents such as nicotinamide cofactors [NAD(P)H]. Visible light‐driven activation of OYEs through NAD(P)H‐free, direct transfer of photoexcited electrons from xanthene dyes to the prosthetic flavin moiety is reported. Spectroscopic and electrochemical analyses verified spontaneous association of rose bengal and its derivatives with OYEs. Illumination of a white light‐emitting‐diode triggered photoreduction of OYEs by xanthene dyes, which facilitated the enantioselective reduction of C=C bonds in the absence of NADH. The photoenzymatic conversion of 2‐methylcyclohexenone resulted in enantiopure (ee >99 %) (R )‐2‐methylcyclohexanone with conversion yields as high as 80–90 %. The turnover frequency was significantly affected by the substitution of halogen atoms in xanthene dyes.     

Visible‐Light Photocatalytic Intramolecular Cyclopropane Ring Expansion

Described herein is a new visible‐light photocatalytic strategy for the synthesis of enantioenriched dihydrofurans and cyclopentenes by an intramolecular nitro cyclopropane ring expansion reaction. Mechanistic studies and DFT calculations are used to elucidate the key factors in this new ring expansion reaction, and the need for the nitro group on the cyclopropane.     

Photocatalysis Enables Visible‐Light Uncaging of Bioactive Molecules in Live Cells

The photo‐manipulation of bioactive molecules provides unique advantages due to the high temporal and spatial precision of light. The first visible‐light uncaging reaction by photocatalytic deboronative hydroxylation in live cells is now demonstrated. Using Fluorescein and Rhodamine derivatives as photocatalysts and ascorbates as reductants, transient hydrogen peroxides were generated from molecular oxygen to uncage phenol, alcohol, and amine functional groups on bioactive molecules in bacteria and mammalian cells, including neurons. This effective visible‐light uncaging reaction enabled the light‐inducible protein expression, the photo‐manipulation of membrane potentials, and the subcellular‐specific photo‐release of small molecules.     

Phosphorene Co‐catalyst Advancing Highly Efficient Visible‐Light Photocatalytic Hydrogen Production

Transitional metals are widely used as co‐catalysts boosting photocatalytic H₂ production. However, metal‐based co‐catalysts suffer from high cost, limited abundance and detrimental environment impact. To date, metal‐free co‐catalyst is rarely reported. Here we for the first time utilized density functional calculations to guide the application of phosphorene as a high‐efficiency metal‐free co‐catalyst for CdS, Zn_0.8Cd_0.2S or ZnS. Particularly, phosphorene modified CdS shows a high apparent quantum yield of 34.7 % at 420 nm. This outstanding activity arises from the strong electronic coupling between phosphorene and CdS, as well as the favorable band structure, high charge mobility and massive active sites of phosphorene, supported by computations and advanced characterizations, for example, synchrotron‐based X‐ray absorption near edge spectroscopy. This work brings new opportunities to prepare highly‐active, cheap and green photocatalysts.