Visible-Light-Induced Organic Photochemical Reactions through Energy-Transfer Pathways

Light can be considered an ideal reagent for environmentally friendly, 'green' chemical synthesis; unlike many conventional reagents, light is non-toxic, generates no waste, and can be obtained from renewable sources. Nevertheless, the need for high-energy ultraviolet radiation in most organic photochemical processes has limited both the practicality and environmental benefits of photochemical synthesis on industrially relevant scales. This perspective describes recent approaches to the use of metal polypyridyl photocatalysts in synthetic organic transformations. Given the remarkable photophysical properties of these complexes, these new transformations, which use Ru(bpy)(3)(2+) and related photocatalysts, can be conducted using almost any source of visible light, including both store-bought fluorescent light bulbs and ambient sunlight. Transition metal photocatalysis thus represents a promising strategy towards the development of practical, scalable industrial processes with great environmental benefits.

In the last few years, visible-light initiated organic transformations have attracted increasing attention. The development of visible-light-promoted photocatalytic reactions, which enable rapid and efficient synthesis of fine chemicals, is highly desirable from the viewpoint of cost, safety, availability, and environmental friendliness. In this Minireview, recent advances made in this fast developing area of research are discussed.