Remarkable variations in the luminescence of frozen solutions of [Au{C(NHMe)2}2](PF6)•0.5(acetone).: Structural and spectroscopic studies of the effects of anions and solvents on gold(I) carbene complexes

The unusual luminescence behavior of the two-coordinate gold(l) carbene complex, [Au{C(NHMe)(2)}(2)](PF6).0.5(acetone), is reported. Upon freezing in a liquid N-2 bath, the colorless, nonluminescent solutions of [Au{C(NHMe)(2)}(2)](PF6).0.5(acetone) become intensely luminescent. Strikingly, the colors of the emission differ in different solvents and appear only after the solvent has frozen. Solid [Au{C(NHMe)(2)}(2)](PF6).0.5 (acetone) is also luminescent, and the luminescence is attributed to the formation of extended chains of gold(l) centers that are connected through aurophilic attractions. Crystallographic studies of [Au{C(NHMe)(2)}(2)](PF6).0.5(acetone) and [Au{C(NHMe)(2)}(2)](BF4), which is also luminescent, reveal that both involve extended chains of cations and that the anions are hydrogen bonded to the cations through cation N-H groups. However, these chains differ in the Au...Au separations in each and in the carbene ligand orientations. In contrast, [Au{C(NMe2)(NHMe)}(2)](PF6) forms a colorless, nonluminescent solid, and in that solid there are no Au...Au interactions, a factor which supports the contention that aggregated species are responsible for the luminescence of [Au{C(NHMe)(2)}(2)](PFe6).0.5(acetone) in the solid state and in frozen solutions.