Highly Efficient Transition Metal Nanoparticle Catalysts in Aqueous Solutions

Abstract

A ligand design is proposed for transition metal nanoparticle (TMNP) catalysts in aqueous solution. Thus, a tris(triazolyl)-polyethylene glycol (tris-trz-PEG) amphiphilic ligand, 2, is used for the synthesis of very small TMNPs with Fe, Co, Ni, Cu, Ru, Pd, Ag, Pt, and Au. These TMNP-2 catalysts were evaluated and compared for the model 4-nitrophenol reduction, and proved to be extremely efficient. High catalytic efficiencies involving the use of only a few ppm metal of PdNPs, RuNPs, and CuNPs were also exemplified in Suzuki-Miyaura, transfer hydrogenation, and click reactions, respectively.

From Mono to Tris-1,2,3-triazole-Stabilized Gold Nanoparticles and Their Compared Catalytic Efficiency in 4-Nitrophenol Reduction

“…The optimizations of Au and ligand mole ratios with variations of SPBs, TEM sizes, and 4-NP reaction rates were thus investigated, and a best result was obtained with the stoichiometry of ligand 5: Au III of 1:1 with the smallest AuNP core size and highest reaction rate. 10 The positive influence on catalysis of the tris-trz ligand bulk in 5 near the AuNP-5 surface was also confirmed by comparison between the multiplicity of the mono-versus tris-trz ligand containing the same PEG tail (AuNP-4 and AuNP-5, respectively). 10 Comparison between AuNP-5 stabilized by the ligand 5 and AuNP-6 stabilized by the widely used commercial polymer polyvinylpyrrolidone 16 (PVP, Mw = 10 000, 90 monomer Inorg.…”

“…10 The positive influence on catalysis of the tris-trz ligand bulk in 5 near the AuNP-5 surface was also confirmed by comparison between the multiplicity of the mono-versus tris-trz ligand containing the same PEG tail (AuNP-4 and AuNP-5, respectively). 10 Comparison between AuNP-5 stabilized by the ligand 5 and AuNP-6 stabilized by the widely used commercial polymer polyvinylpyrrolidone 16 (PVP, Mw = 10 000, 90 monomer Inorg. Chem.…”

“…To obtain smaller AuNPs, 3 equiv of ligand 4 versus HAuCl 4 was used, and the core size of AuNP-4 was reduced to 3.1 ± 0.3 nm ( Figure 2d) with a SPB of 515 nm in the UV−vis spectrum. The 4-NP reaction rate increased to 24.9 × 10 −3 s −1 (k app ), 10 which is one of the highest records among rates of 4-NP reduction compared with the recent literature (Table S1).…”

“…With this goal, the known monotrz-substituted PEG 4 was then used to encapsulate AuNPs, and under conditions identical to the above-mentioned AuNP preparations the use of 1 equiv of the monotrzsubstituted PEG 4 led to the known AuNP-4 with the SPB of 524 nm and AuNP core size measured by TEM of 5.8 ± 0.4 nm. 10 The 4-NP reduction rate catalyzed by AuNP-4, 20.9 × 10 −3 s −1 (k app ), was higher than that of AuNP-3, but the AuNP size was larger than expected. To obtain smaller AuNPs, 3 equiv of ligand 4 versus HAuCl 4 was used, and the core size of AuNP-4 was reduced to 3.1 ± 0.3 nm ( Figure 2d) with a SPB of 515 nm in the UV−vis spectrum.…”

Triazole‐based ligands functionalized silica: Effects of ligand denticity and donors on catalytic oxidation activity of Pd nanoparticles

“…[10] On the contrary, the heterogeneous Pd NPs catalysts require only molecular oxygen as oxidant and are reusable with usually low metal contamination in the oxidized products. [11][12][13] Although chemically robust, N-rich aromatic triazole compounds have been demonstrated as good stabilizers for MNPs, [14] only a handful of examples involving Pd NPs catalysts supported by triazole-functionalized solid supports have so far been reported. [11][12][13] Although chemically robust, N-rich aromatic triazole compounds have been demonstrated as good stabilizers for MNPs, [14] only a handful of examples involving Pd NPs catalysts supported by triazole-functionalized solid supports have so far been reported.…”