Heteroleptic copper complexes with nitrogen and phosphorus ligands in photocatalysis: Overview and perspectives

Heteroleptic [Cu(NˆN)(PˆP)] + complexes are receiving increasing interest for various photocatalytic applications and energy utilizations. This review compiles the genesis of this class of complexes and their properties, as well as their use in catalysis. Their wide-ranging applicability is highlighted by recent examples that showcase their ability to replace noble-metal-based photosensitizers to establish more sustainable photocatalytic processes. Modern chemistry is experiencing a shift toward developing affordable and clean-energy-based processes in accordance with UN Sustainable Development Goals 7 and 13. In this respect, sunlight-initiated or -mediated photochemical transformations have broad interest as green alternatives for the synthesis of chemicals and sustainable energy carriers. Heteroleptic copper complexes hold significant potential for noble-metal-free photocatalysis and photochemistry. This review highlights the development of [Cu(NˆN)(PˆP)] + complexes with tunable and available diphosphine and diimine ligands. Their photophysical and chemical properties are studied and introduced by a discussion of model reactions giving a fundamental understanding of the activity of these complexes. Their most important applications in photo-catalyzed transformations, particularly proton and CO 2 reduction, together with other photochemical applications, such as sensors, are presented. Copper complexes bearing nitrogen- and phosphorus-based ligands have emerged as promising alternatives to established photoredox catalysts based on precious metals while offering partially complementary reactivities. This review introduces fundamental properties of heteroleptic [Cu(NˆN)(PˆP)] + complexes and showcases their modular construction. Their versatility as photosensitizers in energy-related applications, such as proton and carbon dioxide reduction, the construction of sensors, and synthetic transformations, is highlighted according to recent literature. Remaining challenges and future perspectives are emphasized and discussed.