Studies on the reactions of [AuCl₄]⁻ with different nucleophiles in aqueous solution

Abstract

In order to distinguish between the different types of reactions that can occur between Au(III) species and simple nucleophiles, including iodide, bromide, nitrite, thiourea, pyridine and dimethyl sulfoxide, spectrophotometric techniques including stopped-flow and rapid-scan measurements were employed under specific reaction conditions. All experiments were performed in a 0.4 M NaCl aqueous solution to maintain a high chloride concentration and a constant ionic strength. The temperature dependence of the observed rate constants confirmed the associative nature of the ligand substitution reactions. The redox behaviour of the Au(III) species was studied by cyclic voltammetry and confirmed the reversible redox transitions at ca. 0.38 V (SCE, E = 0.1 V s(-1)). Results obtained during the reaction progress were attributed to the formation of Au(0). This oxidation state was observed for the reactions with thiourea, iodide and nitrite, whereas pyridine showed a potential shift only to Au(i) formation, while bromide showed potential shifts typical of ligand substitution reactions. The reaction with dimethyl sulfoxide was studied using (1)H NMR and ab initio (RMP2(full)/LANL2DZp) techniques, which revealed why Au(III) does not react with sulfoxide. The results are discussed in terms of the importance of the stability of the Au(III) species in aqueous solutions of the selected salts and bases. In this way, one could differentiate between a possible three-electron inner-sphere redox process and/or a substitution process during the rapid initial step of the reactions.

Design-controlled synthesis of IrO2 sub-monolayers on Au nanoflowers: marrying plasmonic and electrocatalytic properties

“…This agrees with the AuCl 4 − being reduced to AuCl 2 − . 73,74 No LSPR peaks assigned to Au nanoparticles were observed, indicating that no further reduction to Au 0 takes place simply by mixing the precursors. Interestingly, under otherwise identical conditions, the (Fig.…”

Self‐Assembled Monolayer Stabilized Gold‐Vanadate Nanoflute for Water Splitting Reactions

“…The cyclic voltammetry of the material exhibited different cathodic and anodic signals (Figure S2b). The anodic peak at 1.7 V was due to oxidation of Au (0) to Au (I) . The presence of such signal for Au(0)/Au(I) couple clearly suggested that the Au particles in the material was mostly in zero oxidation state and was in accordance with the XRD and DRS study .…”

“…The anodic peak at 1.7 V was due to oxidation of Au (0) to Au (I) . The presence of such signal for Au(0)/Au(I) couple clearly suggested that the Au particles in the material was mostly in zero oxidation state and was in accordance with the XRD and DRS study . The other dominant cathodic peak at −1.1 V and its corresponding anodic peak almost at the same potential was due to the [VO 2 ] 2− /[VO 2 ] 3− couple (Figure S2b) .…”

Ultrasensitive Detection of a Variety of Analytical Targets Based on a Functionalized Low‐Resistance AuNPs/β‐Ni(OH)2 Nanosheets/Ni Foam Sensing Platform

“…As further confirmed by XRD spectra (Figure d, curve III with blue color), the peak positions labeled by triangle at 2θ = 38.2°, 44.4°, 64.6°, 77.5°, 81.7°, and 98.1° corresponding to the (111), (200), (220), (311), (222), and (400) planes were in good agreement with Au (JCPDs, 04–0784). The reaction to form AuNPs can be described as: …”