Complexes with Atomic Gold Ions: Efficient Bis-Ligand Formation

Complexes of atomic gold with a variety of ligands have been formed by passing helium nanodroplets (HNDs) through two pickup cells containing gold vapor and the vapor of another dopant, namely a rare gas, a diatomic molecule (H(2), N(2), O(2), I(2), P(2)), or various polyatomic molecules (H(2)O, CO(2), SF(6), C(6)H(6), adamantane, imidazole, dicyclopentadiene, and fullerene). The doped HNDs were irradiated by electrons; ensuing cations were identified in a high-resolution mass spectrometer. Anions were detected for benzene, dicyclopentadiene, and fullerene. For most ligands L, the abundance distribution of AuL(n)(+) versus size n displays a remarkable enhancement at n = 2. The propensity towards bis-ligand formation is attributed to the formation of covalent bonds in Au(+)L(2) which adopt a dumbbell structure, L-Au(+)-L, as previously found for L = Xe and C(60). Another interesting observation is the effect of gold on the degree of ionization-induced intramolecular fragmentation. For most systems gold enhances the fragmentation, i.e., intramolecular fragmentation in AuL(n)(+) is larger than in pure L(n)(+). Hydrogen, on the other hand, behaves differently, as intramolecular fragmentation in Au(H(2))(n)(+) is weaker than in pure (H(2))(n)(+) by an order of magnitude.