Photophysical and Theoretical Studies on Luminescent Tetranuclear Coinage Metal Building Blocks

The synthesis, structural characterization, and the study of the photophysical properties of complexes [Au2Ag2(C6F5)4(N⋮CCH3)2] n (1) and [Au2Cu2(C6F5)4(N⋮CCH3)2] n (2) have been carried out. The crystal structure of both complexes consists of polymeric chains formed by repetition of Au2Ag2 or Au2Cu2 units built up by metallophilic Au(I)···M(I) interactions that are linked through Au(I)···Au(I) interactions. Complexes 1 and 2 are brightly luminescent in the solid state at room temperature and at 77 K with lifetimes in the nanosecond range. Both compounds 1 and 2 undergo oligomerization in solution, as observed through UV−vis and excitation spectra in acetonitrile solutions at high concentrations. Thus, a correlation between the excitation spectra in solution at different concentrations and the absorption spectra in the solid state for complex 1 can be established. Time-dependent DFT calculations agree well with the experimental results and support the idea of that the origin of the luminescence of these complexes arises from orbitals located in the tetranuclear Au2M2 units.