Heteroleptic diimine-diphosphine Cu(I) complexes as an alternative towards noble-metal based photosensitizers: Design strategies, photophysical properties and perspective applications

Photoactive Cu(I) complexes are considered as a promising alternative to traditional noble-metal complexes that are mainly based on Ru(II) and Ir(III). Therefore, in recent years heteroleptic Cu(I) complexes of the type [Cu((NN)-N-boolean AND)((PP)-P-boolean AND)](+) have been developed exhibiting impressive performance, e.g., long-lived excited-states, high emission quantum yields with tunable emission spectra as well as largely adjustable redox properties. These favorable features render heteroleptic Cu(I) complexes as suitable non-noble metal photosensitizers. Due to the exploding number of examples reported in literature, this review aims at systematically comparing the fundamental features of various cationic and neutral diimine-diphosphine Cu(I) complexes regarding to their geometrical, optical as well as electrochemical properties. In particular, this review focuses on the ability to tune the optoelectronic properties and excited-state dynamics by the design and the choice of the underlying (NN)-N-boolean AND and (PP)-P-boolean AND chelate ligands. Finally, this review briefly indicates some application scenarios of these novel class of complexes, e.g., in the fields of photo catalytic hydrogen evolution and light-emitting devices. As a result this review likes to contribute to a detailed understanding of structure-function relationships and to the rational design of heteroleptic diimine-diphosphine Cu(I) complexes for specific photophysical applications in the future. (C) 2017 Elsevier B.V. All rights reserved.