Luminescent characterization of solution oligomerization process mediated gold-gold interactions. DFT calculations on [Au2Ag2R4L2](n) moieties

The optical properties of [Au2Ag2(C6F5)(4)(OCMe2)(2)](n) (1) have been stud ied in the solid state at room temperature and at 77 K and in acetone solut ion (5 x 10(-4) M). The crystal structure of 1, analyzed by X-ray diffracti on, consists of polymeric chains formed by repetition of Au2Ag2 moieties li nked through short gold-gold interactions. The emission profile observed fo r 1 in dilute acetone solution (5 x 10(-4) M) is assignable to pentafluorop henyl localized pi pi* excited states or from pi-MMCT transitions, and in t he solid-state arises from metal-centered (d sigma*)(1)(p sigma)(1) or (d d elta*)(1)(p sigma)(1) excited states. When the absorption and emission spec tra of compound 1 in acetone are registered at different concentrations, th ey display a band that does not obey the Lambert-Beer law. This deviation i s consistent with molecular aggregation in solution through gold-gold inter actions, and a clear correlation between the emission wavelength and the st ructure 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 o rbitals involved in each transition.