Luminescent Characterization of Solution Oligomerization Process Mediated Gold−Gold Interactions. DFT Calculations on [Au₂Ag₂R₄L₂]nMoieties

The optical properties of [Au 2 Ag 2 (C 6 F 5 ) 4 (OCMe 2 ) 2 ] n ( 1 ) have been studied in the solid state at room temperature and at 77 K and in acetone solution (5 × 10 - 4 M). The crystal structure of 1, analyzed by X-ray diffraction, consists of polymeric chains formed by repetition of Au 2 Ag 2 moieties linked through short gold−gold interactions. The emission profile observed for 1 in dilute acetone solution (5 × 10 - 4 M) is assignable to pentafluorophenyl localized ππ* excited states or from π-MMCT transitions, and in the solid-state arises from metal-centered (dσ*) 1 (pσ) 1 or (dδ*) 1 (pσ) 1 excited states. When the absorption and emission spectra of compound 1 in acetone are registered at different concentrations, they display a band that does not obey the Lambert−Beer law. This deviation is consistent with molecular aggregation in solution through gold−gold interactions, and a clear correlation between the emission wavelength and the structure of 1 in the solid state and in solution is shown. DFT calculations accord with the observed experimental behavior and show the nature of the orbitals involved in each transition.