Gas phase synthesis and reactivity of Ag-n(+) and Agn-1H+ cluster cations

Multi-stage mass spectrometry (MSn) on [(M+ Ag-H)(x)+Ag](+) precursor ions (where M=an amino acid such as glycine or N,N-dimethylglycine) results in the formation of stable silver (Ag-3(+), Ag-5(+) and Ag-7(+)) and silver hydride (Ag2H+, Ag4H+ and Ag6H+) cluster cations in the gas phase. Deuterium labelling studies reveal that the source of the hydride can be either from the alpha carbon or from one of the heteroatoms. When M=glycine, the silver cyanide clusters Ag4CN+ and Ag-5(H, C, N)(+) are also observed. Collision induced dissociation (CID) and DFT calculations were carried out on each of these clusters to shed some light on their possible structures. CID of the Ag-n(+) and Agn-1H+ clusters generally results in the formation of the same Ag-n-2(+) product ions via the loss of Ag-2 and AgH respectively. DFT calculations also reveal that the Ag-n(+) and Agn-1H+ clusters have similar structural features and that the Agn-1H+ clusters are only slightly less stable than their all silver counterparts. In addition, Ag-n(+) and Agn-1H+ clusters react with 2-propanol and 2-butylamine via similar pathways, with multiple ligand addition occurring and a coupled deamination-dehydration reaction occurring upon condensation of a third (for Ag2H+) or a fourth (for all other silver clusters) 2-butylamine molecule onto the clusters. Taken together, these results suggest that the Ag-n(+) and Agn-1H+ clusters are structurally related via the replacement of a silver atom with a hydrogen atom. This replacement does not dramatically alter the cluster stability or its unimolecular or bimolecular chemistry with the 2-propanol and 2-butylamine reagents.