Excited state properties of bis(trimethylsilyl)acetylenecopper(I) hexafluoroacetylacetonate. Emission and photodissociation induced by metal-to-ligand charge transfer excitation

The complex CuI(BTA)(hfac) with BTA=bis(trimethylsilyl)acetylene and hfac=1,1,1,5,5,5-hexa-fluoroacetylacetonate shows a longest-wavelength absorption at at λmax=324 nm (ε=5400 M−1 cm−1) which is assigned to a spin-allowed CuI→π* (BTA) metal-to-ligand charge transfer (MLCT) transition. The solid complex displays an emission at λmax=601 nm which is assumed to originate from the lowest-energy MLCT triplet. In solution MLCT excitation leads to the release of the acetylene with 6×10−4 at λirr=333 nm.