Influence of a Tunable Band Gap on Photoredox Catalysis by Various Two-Dimensional Transition-Metal Dichalcogenides

Transition-metal dichalcogenides (TMDs) show a diverse range of properties and are highly promising for organic transformations owing to their large surface-to-volume ratio that confers good selectivity and sensitivity by increasing the number of active sites. Herein, we have prepared the semiconducting (2H) and mixed-phase (2D) TMDs by mechanical and chemical exfoliation, respectively. The materials have been characterized by various forms of spectroscopy and microscopy. Further, we have explored the potential of the four classes of TMDs to participate in aerobic oxidative coupling of amines to imines upon irradiation with visible light. Our efforts are directed toward determining the most suitable material for this reaction at conditions that are not too harsh. 2H WSe2 is most effective for the transformation, most likely because of a suitable band gap. Given their broad applications, these materials can be of interest in several industrial synthetic pathways as well.