Nanochemistry in the Gas Phase: Coulombic Adducts of Atomically Precise Noble Metal Nanoclusters and Their Concomitant Reactions.

In this study, we explore for the first time interactions of atomically precise noble metal nanoclusters (NCs) in the gas phase, revealing fundamental nanoscale reactivity beyond solvent effects. Using ion-selected mass spectrometry and theoretical calculations, we investigate and establish the formation of a Coulombic ion pair between two oppositely charged NC ions, [Ag17(o1-CBT)12]3- (o1-CBT = ortho-1-carboranethiol) and [Cu14(o9,12-CBDT)6]+ (o9,12-CBDT = ortho-9,12-carboranedithiol), that undergo metal exchange to form alloy NCs, focusing on how atom exchange processes can be understood in the isolated gas phase. The Coulombic contribution to the binding energy of the NC ion pair was estimated to be ∼66%, while the rest was from intercluster ligand interaction through van der Waals forces. Similar behavior across diverse oppositely charged NC ion pairs, including [Ag29(1,3-BDT)12]3- (1,3-BDT = 1,3-benzenedithiol), [PdAg28(1,3-BDT)12]4-, [PtAg28(1,3-BDT)12]4-, [Ag13Cu4(o1-CBT)12]3-, [Au25(2-PET)18]- (2-PET = 2-phenylethanethiol), [PdAg24(2,4-DMBT)18]2- (2,4-DMBT = 2,4-dimethylbenzenethiol), [PtAg24(2,4-DMBT)18]2-, [Cu14(o9,12-CBDT)6]+, [Ag21(m9-CBT)12]+ (m9-CBT = meta-9-carboranethiol), and [Ag22(2,5-DMBT)12Cl4(DPPB)4]+ (DPPB= diphenylphosphenobutane), confirms the universality of this process. Dithiol ligand exchange was observed between [Ag29(1,3-BDT)12]3- and [Cu14(o9,12-CBDT)6]+ in their Coulombic adducts for the first time. These results highlight the intrinsic, solvent-independent reactivity of NCs in the gas phase.