Charge-Transfer Effects in Ligand Exchange Reactions of Au₂₅ Monolayer-Protected Clusters

Abstract

Reported here are second-order rate constants of associative ligand exchanges of Au25L18 nanoparticles (L = phenylethanethiolate) of various charge states, measured by proton nuclear magnetic resonance at room temperature and below. Differences in second-order rate constants (M(-1) s(-1)) of ligand exchange (positive clusters ∼1.9 × 10(-5) versus negative ones ∼1.2 × 10(-4)) show that electron depletion retards ligand exchange. The ordering of rate constants between the ligands benzeneselenol > 4-bromobenzene thiol > benzenethiol reveals that exchange is accelerated by higher acidity and/or electron donation capability of the incoming ligand. Together, these observations indicate that partial charge transfer occurs between the nanoparticle and ligand during the exchange and that this is a rate-determining effect in the process.

Ligand Structure Determines Nanoparticles' Atomic Structure, Metal-Ligand Interface and Properties

“…Ligand exchange protocols on AuNMs are a highly versatile strategy that is employed to tune the synthesis to obtain new nanomolecules that are difficult to obtain via direct Brust method (Brust et al, 1994 ; Hostetler et al, 1999 ). Ligand exchange reactions on molecular pure AuNMs allows us to investigate the influence of thiolate ligand on AuNMs' structure and to understand the fundamental aspects of ligand effect on structural selectivity (Kurashige et al, 2012 ; Indrasekara et al, 2014 ; Carducci et al, 2015 ; Higaki et al, 2016 ). It has been demonstrated by many, that a distinct AuNMs can be converted to a new one via ligand exchange in the presence of a physicochemically different ligand (Kamei et al, 2011 ; Zeng et al, 2013 ; Nimmala et al, 2014a , 2015 ; Bootharaju et al, 2015 ; Rambukwella et al, 2017b ).…”

Deepening the Understanding of Thiolate-Protected Metal Clusters Using High-Performance Liquid Chromatography

“…Their results indicated how the reaction rate depends on the introduced ligand and what type of chemical composition distribution appears in the prod-ucts. 403,420,620,653,654,885,886,888,890,891,922 They also predicted that in these reactions, preferential exchange sites exist where the reaction is more likely to occur. 620,891 To identify these preferential exchange sites, Ackerson and co-workers later crystallized the reaction products, Au 25 (SC 2 H 4 Ph) 16 ( p-BBT) 2 ( p-BBT = para-bromobenzenethiolate) and Au 102 ( p-MBA) 40 -( p-BBT) 4 .…”

“…Hence, our HPLC allows other functionalities to be added to the clusters. 40,41,43,46,53,58,61,62,74,80,125,130,138,147,149,159,162,166,197 888,890,891,915,916,922,932,936939 Furthermore, such ligandexchange reactions can be also used for size-selective synthesis of Au n (SR) m clusters, which are difficult to prepare directly. 46,53,61,62,80,138,149,159,264,301,306,467,484,491,515,571,628,633,637,662,744747,769,772,…”

The molecular mechanism of the ligand exchange reaction of an antibody against a glutathione-coated gold cluster

“…18,19 Au 25 (SR) 18 − clusters have been widely used for ligand exchange reactions. [20][21][22][23][24][25][26] The fact that this cluster includes dimeric staple motifs 27 introduces a higher degree of complexity with respect to the reaction involving monomeric staples ( Fig. 1), as it is not obvious a priori whether the sulfur atom participating in the reaction (the thiolate being exchanged) will be the apex one or the side one ( Fig.…”