Kinetics of Cationic-Ligand-Exchange Reactions in Au₂₅ Nanoclusters

Abstract

Herein, we report the first investigation into the kinetics of cationic-ligand-exchange processes through the reaction of Au 25 (SCH 2 CH 2 Ph) 18 with a cationic thiol HS(CH 2 ) 11 N(CH 3 ) 3 + , which resulted in different populations of the two thiolate ligands (SR 0 and SR + ), that is, Au 25 (SR 0 ) 18−x (SR + ) x . The ligand-exchange process was monitored by electrospray ionization mass spectrometry, and the reaction kinetics is discussed in combination with 1 H NMR results; these techniques reveal that the kinetics of the cationic-ligand-exchange process, which is different from a typical neutral-thiol-to-neutral-thiol ligand exchange, is strongly dependent on how the SR + ligands interact with each other during the ligand-exchange process. There are two main factors that determine the unique reaction kinetics, namely, Coulombic repulsions (i) between the attached SR + ligands and free ligands in solution, which hinder further ligand exchange, and (ii) among the surface SR + ligands on the thiolate monolayer, which promote the thermal decomposition of the nanocluster.

Biocompatible gold nanoclusters: synthetic strategies and biomedical prospects

“…A MBA-protected Au 144 NCs was similarly prepared and characterized [53]. Remarkably, it was shown that the coordinating ligands at the surface of the AuNCs can be easily exchanged with free thiolates in aqueous solution at neutral pH and in a SN 2 -like mechanism [54]. This ligand-exchange property is extremely important and opens the possibility to prepare highly monodisperse AuNCs with further post-functionalization abilities.…”

The emergence of mass spectrometry for characterizing nanomaterials. Atomically precise nanoclusters and beyond

“…Murray and co-workers studied Au25 NCs with ligand-exchanged mixed monolayers (thiophenolate, hexanethiolate, or biotinylated ligands) using ESI-MS. 116,117 Mass spectrometry was again powerful for characterizing ligand exchange reactions in protected nanoclusters with selenolates or Tellurolates. [118][119][120][121] Again, time dependent experiments have permitted to push forward the understanding of the formation of Please do not adjust margins Please do not adjust margins cluster size conversion or surface ligand modifications as a function of ligand exchange strategies, [122][123][124][125][126] reactive agents [127][128][129][130][131][132][133] or etching process. 134,135 Probing the charge state of the metal core (or kernel) of nanoclusters is also an exciting field of investigation.…”

Absolute configuration retention of a configurationally labile ligand during dynamic processes of thiolate protected gold clusters

“…10,11 Preparation of Au n (SR) m nanoclusters is normally done through direct synthesis using neutral and anionic thiolate ligands. 12 However, due to the low solubility and steric and electrostatic effects, some ligands cannot be used in direct synthesis, which severely limits the diversity of surface properties of the accessible clusters. 13,14 Ligand exchange reactions (LERs), which introduce new ligands to the parent nanoclusters, [15][16][17][18][19][20] are widely applied for adding functionalities or chemical properties to clusters as a versatile post-modification method.…”