Recent Developments on Visible‐Light Photoredox Catalysis by Organic Dyes for Organic Synthesis

In the past few decades, energy issues have become so important that numerous scientific investigations have sought the development of new sustainable energy resources. Utilization of solar energy is the most useful alternative sustainable energy source as its abundance is "virtually unlimited" and free. It is also well known that solar light contains 43% visible light. Therefore, visible-light photoredox catalysis has attracted considerable attention in synthetic organic chemistry as it provides an energetically beneficial pathway for green synthesis. Commonly, polypyridine complexes of ruthenium and iridium have been utilized as visible-light photocatalysts in most of these reactions. Recently, organic dyes have been used as an attractive alternative to transition metal complexes in visible-light-driven photoredox catalysis. We summarize general mechanism, key photophysical properties of dyes, and recent applications of organic dyes as a visible-light photocatalyst in organic synthesis.