Basic Concepts and Activation Modes in Visible-Light-Photocatalyzed Organic Synthesis

Abstract

AbstractVisible light photocatalysis has established itself as a promising sustainable and powerful strategy to access reactive intermediates, i.e. radicals and radical ions, under mild reaction conditions using visible light irradiation. This field enables the development of formerly challenging or even previously inaccessible organic transformations. In this tutorial review, an overview of the essential concepts and techniques of visible-light-mediated chemical processes and the most common types of photochemical activation of organic molecules, i.e. photoredox catalysis and photosensitization, are discussed. Selected photocatalytic alkene functionalization reactions are included as examples to illustrate the basic concepts and techniques with particular attention given to the understanding of their reaction mechanisms.1 Introduction2 Photocatalysts3 Photophysical and Electrochemical Properties3.1 Excited-State Energy3.2 Ground-State Redox Potentials3.3 Excited-State Redox Potentials3.4 Local Absorbance Maximum for Lowest Energy Absorption3.5 Excited-State Lifetime3.6 [Ru(bpy)3]2+ as a Case Study3.7 Basic Laws and Equations of Photochemistry and Photocatalysis3.8 Common Terminology in Photochemistry and Photocatalysis4 Activation Modes in Photocatalysis4.1 Photoinduced Electron Transfer4.2 Photoinduced Energy Transfer5 Conclusions and Outlook