Copper(I) complexes with simple inorganic ligands having no acceptor orbitais of low energy (e.g. Cl-, Br-, I-, and NH3) are characterized by CTTS photochemistry. UV excitation of halocuprates(I) in aqueous solutions leads to the formation of a hydrated electron, which undergoes competitive recombination and scavenging reactions. The mechanism of the whole photoinduced redox process in these systems is rather medium-dependent and involves the formation and decay of hydride intermediates. Cyano (as pseudohalo) as well as mixed-ligand cyano-halo complexes of Cu(I) show similar photoredox features, demonstrating the dominance of CTTS reactivity. On the basis of their very remarkable luminescence properties, however, CTTS (or metal-centered 3d94s1) excited states of these coordination compounds can decay via formation of emissive intermediates, which also eject an electron. This route is interpreted by an exciplex mechanism, which apparently plays an important role in the photoinduced charge-transfer properties of the homo- and heteroleptic halocuprates(I). Cluster complexes of the type Cu4X4L4 (X- = halide, L = organic amine) show remarkably rich photophysics. Multiple emissions have been observed, but excited-state assignments are somewhat ambiguous. The photochemistry of these materials has yet to be extensively studied, although some bimolecular redox reactions have been reported. Copper(I) complexes with polypyridine ligands are featured by MLCT reactivity. Formation of an exdplex (but non-emissive) via quenching of these excited states is also an essential reaction of these compounds. Differing from the CTTS character, however, they undergo photoinduced electron transfer only by means of direct redox quenching. Two-photon photochemistry is also shown by these complexes. MLCT excited states of other cationic copper(I) complexes have been involved in both intra- and inter-molecular reactions via oxidative quenching. Photocatalytic applications of Cu(I) coordination com- pounds are also demonstrated.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry