Kinetics of Intercluster Reactions between Atomically Precise Noble Metal Clusters [Ag25(DMBT)18]- and [Au25(PET)18]- in Room Temperature Solutions

Marco Neumaier; Ananya Baksi; Patrick Weis; Erik K Schneider; Papri Chakraborty; Horst Hahn; Thalappil Pradeep; Manfred M Kappes

doi:10.1021/jacs.1c01140

Kinetics of Intercluster Reactions between Atomically Precise Noble Metal Clusters [Ag₂₅(DMBT)₁₈]^- and [Au₂₅(PET)₁₈]^- in Room Temperature Solutions

J Am Chem Soc. 2021 May 12;143(18):6969-6980. doi: 10.1021/jacs.1c01140. Epub 2021 Apr 29.

Authors

Marco Neumaier¹, Ananya Baksi¹, Patrick Weis², Erik K Schneider², Papri Chakraborty^{1

2}, Horst Hahn¹, Thalappil Pradeep³, Manfred M Kappes^{1

2}

Affiliations

¹ Institute of Nanotechnology, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany.
² Institute of Physical Chemistry, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany.
³ DST Unit of Nanoscience and Thematic Unit of Excellence, Indian Institute of Technology Madras, 600 036 Chennai, India.

PMID: 33913724
DOI: 10.1021/jacs.1c01140

Abstract

The kinetics of intercluster metal atom exchange reactions between solvated [Ag₂₅(DMBT)₁₈]^- and [Au₂₅(PET)₁₈]^- (DMBT and PET are 2,4-dimethylbenzenethiol and 2-phenylethanethiol, respectively, both C₈H₁₀S) were probed by electrospray ionization mass spectrometry and computer-based modeling. Anion mass spectra and collision induced dissociation (CID) measurements show that both cluster monomers and dimers are involved in the reactions. We have modeled the corresponding kinetics assuming a reaction mechanism in which metal atom exchange occurs through transient dimers. Our kinetic model contains three types of generic reactions: dimerization of monomers, metal atom exchange in the transient dimers, and dissociation of the dimers to monomers. There are correspondingly 377 discrete species connected by in total 1302 reactions (i.e., dimerization, dissociation and atom exchange reactions) leading to the entire series of monomeric and dimeric products [Ag_mAu_25-m]^- (m = 1-24) and [Ag_mAu_50-m]^2- (m = 0-50), respectively. The rate constants of the corresponding reactions were fitted to the experimental data, and good agreement was obtained with exchange rate constants which scale with the probability of finding a silver or gold atom in the respective monomeric subunit of the dimer, i.e., reflecting an entropic driving force for alloying. Allowing the dimerization rate constant to scale with increasing gold composition of the respective reactants improves the agreement further. The rate constants obtained are physically plausible, thus strongly supporting dimer-mediated metal atom exchange in this intercluster reaction system.