Interparticle Reactions between Silver Nanoclusters Leading to Product Cocrystals by Selective Cocrystallization

We
present an example of an interparticle reaction between atomically
precise nanoclusters (NCs) of the same metal, resulting
in entirely different clusters. In detail, the clusters [Ag12(TBT)8(TFA)5(CH3CN)]+ (TBT = tert-butylthiolate, TFA = trifluoroacetate,
CH3CN = acetonitrile) and [Ag18(TPP)10H16]2+ (TPP = triphenylphosphine) abbreviated
as Ag12 and Ag18, respectively, react leading
to [Ag16(TBT)8(TFA)7(CH3CN)3Cl]+ and [Ag17(TBT)8(TFA)7(CH3CN)3Cl]+, abbreviated
as Ag16 and Ag17, respectively. The two product
NCs crystallize together as both possess the same metal chalcogenolate
shell, composed of Ag16S8, making them indistinguishable.
The occupancies of Ag16 and Ag17 are 66.66 and
33.33%, respectively, in a single crystal. Electrospray ionization
mass spectrometry (ESI MS) of the reaction product and a dissolved
crystal show the population of Ag16 and Ag17 NCs to be in a 1:1 and 2:1 ratio, respectively. This suggests selective
crystallization in the cocrystal. Time-dependent ESI MS was employed
to understand the formation of product clusters by monitoring the
reaction intermediates formed in the course of the reaction. We present
an unprecedented growth mechanism for the formation of silver NCs
mediated by silver thiolate intermediates.