gold thiolate
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2022 ◽  
Author(s):  
Maya Khatun ◽  
Sayan Paul ◽  
Saikat Roy ◽  
Subhasis Dey ◽  
Anakuthil Anoop

We present a benchmark study on popular density functionals for their efficiency and accuracy in the geometry and relative stability of gold-thiolate nanoclusters taking Au3(SMe)3 isomers. We have used normalized mean absolute error (NMAE) analysis as a parameter to compare the results with the reference methods - DLPNO-CCSD(T) and RI-SCS-MP2. We have also compared the performance on the thiolate interaction energy of the stable geometries using the results from our benchmark study. One of the promising functional is PBE that shows robust performance for geometry optimization. On the other hand, M06-2X stands out as the proper choice for the relative energies of the clusters. With the selected methods, we have analyzed the gold-sulfur interaction in Au3(SMe)3 and a comparison is made with AuSMe. The bonding analysis has revealed a partial covalency between gold and sulfur atoms in general. On going from AuSMe to Au3(SMe)3, a substantial flow of charge from gold atoms to thiolate ligands as a result of the increase in gold s-d hybridization. As the s-d mixing in Au increases, the main character of Au-S interaction shifts from covalent to ionic. Hence, a covalent-charge-transfer interaction dominates in gold-sulfur bonding and gives rise to a charge-shift bonding.


Molecules ◽  
2021 ◽  
Vol 26 (22) ◽  
pp. 6891
Author(s):  
Guillermo Canudo-Barreras ◽  
Lourdes Ortego ◽  
Anabel Izaga ◽  
Isabel Marzo ◽  
Raquel P. Herrera ◽  
...  

In this work, two thiourea ligands bearing a phosphine group in one arm and in the other a phenyl group (T2) or 3,5-di-CF3 substituted phenyl ring (T1) have been prepared and their coordination to Au and Ag has been studied. A different behavior is observed for gold complexes, a linear geometry with coordination only to the phosphorus atom or an equilibrium between the linear and three-coordinated species is present, whereas for silver complexes the coordination of the ligand as P^S chelate is found. The thiourea ligands and their complexes were explored against different cancer cell lines (HeLa, A549, and Jurkat). The thiourea ligands do not exhibit relevant cytotoxicity in the tested cell lines and the coordination of a metal triggers excellent cytotoxic values in all cases. In general, data showed that gold complexes are more cytotoxic than the silver compounds with T1, in particular the complexes [AuT1(PPh3)]OTf, the bis(thiourea) [Au(T1)2]OTf and the gold-thiolate species [Au(SR)T1]. In contrast, with T2 better results are obtained with silver species [AgT1(PPh3)]OTf and the [Ag(T1)2]OTf. The role played by the ancillary ligand bound to the metal is important since it strongly affects the cytotoxic activity, being the bis(thiourea) complex the most active species. This study demonstrates that metal complexes derived from thiourea can be biologically active and these compounds are promising leads for further development as potential anticancer agents.


Nanoscale ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 4439-4443
Author(s):  
Srestha Basu ◽  
Hussein Fakhouri ◽  
Christophe Moulin ◽  
Santanu Dolai ◽  
Isabelle Russier-Antoine ◽  
...  

Four orders-of-magnitude enhancement in two-photon excited photoluminescence of gold nanoclusters has been observed following complexation with zinc ions.


2020 ◽  
Vol 49 (10) ◽  
pp. 1228-1231
Author(s):  
Midori Murakami ◽  
Riku Matsumine ◽  
Takeya Ono ◽  
Katsuaki Konishi

Molecules ◽  
2020 ◽  
Vol 25 (12) ◽  
pp. 2902
Author(s):  
Freddy R. Escobar-Ledesma ◽  
Carlos F. Aragón-Tobar ◽  
Patricio J. Espinoza-Montero ◽  
Ernesto de la Torre-Chauvin

Thiosulfate leaching combined with ion-exchange resins is an innovative alternative for gold recovery. According to the properties of activated carbon, it could replace resins in the gold recovery process, improve efficiency, and reduce operating cost. In this research, the adsorption process of gold thiosulfate complex on thiol-modified activated carbon was studied. Thioglycolic acid (ATG) was impregnated in activated carbon, and its adsorption ability was tested with synthetic solutions of gold and sodium thiosulfate (Au 10 mg·L−1, Na2S2O3 0.1 mol·L−1, pH = 10.0). Carbon was characterized by infrared spectroscopy, SEM-EDS, PZC titration, hardness number measures, and proximal analysis. Synthetic solutions were also characterized by UV-vis spectroscopy and cyclic voltammetry. The percentage of volatile material increased from 10.0 to 13.9% due to the impregnation process of ATG. Infrared spectra show characteristic bands of C-H, S-H, and C-S bonds. In the adsorption tests, the ATG-impregnated carbon achieved 91% of gold recovery, while the same amount of ATG in the liquid phase stirred with unmodified activated carbon reached 90% of gold recovery. The 44.9% of gold recovered with activated carbon impregnated with ATG was eluted with sodium cyanide ([NaCN] = 0.2 mol·L−1; [NaOH] = 0.25 mol·L−1; [CH3CH2OH] = 30% V/V; pH = 12.0; t = 24 h). These results suggest the gold transferred from the thiosulfate complex to a new gold thiolate complex.


2020 ◽  
Author(s):  
Clément Dulong ◽  
Bruno Madebène ◽  
Susanna Monti ◽  
Johannes Richardi

<div><div><div><p>A new reactive force field based on the ReaxFF formalism is effectively parametrized against an extended training set of quantum chemistry data (containing more than 120 different structures) to describe accurately silver- and silver-thiolate systems. The results obtained with this novel representation demonstrate that the novel ReaxFF paradigm is a powerful methodology to reproduce more appropriately average geometric and energetic properties of metal clusters and slabs when compared to the earlier ReaxFF parametrizations dealing with silver and gold. ReaxFF cannot describe adequately specific geometrical features such as the observed shorter distances between the under-coordinated atoms at the cluster edges. Geometric and energetic properties of thiolates adsorbed on a silver Ag20 pyramid are correctly represented by the new ReaxFF and compared with results for gold. The simulation of self-assembled monolayers of thiolates on a silver (111) surface does not indicate the formation of staples in contrast to the results for gold-thiolate systems.</p></div></div></div>


2020 ◽  
Author(s):  
Clément Dulong ◽  
Bruno Madebène ◽  
Susanna Monti ◽  
Johannes Richardi

<div><div><div><p>A new reactive force field based on the ReaxFF formalism is effectively parametrized against an extended training set of quantum chemistry data (containing more than 120 different structures) to describe accurately silver- and silver-thiolate systems. The results obtained with this novel representation demonstrate that the novel ReaxFF paradigm is a powerful methodology to reproduce more appropriately average geometric and energetic properties of metal clusters and slabs when compared to the earlier ReaxFF parametrizations dealing with silver and gold. ReaxFF cannot describe adequately specific geometrical features such as the observed shorter distances between the under-coordinated atoms at the cluster edges. Geometric and energetic properties of thiolates adsorbed on a silver Ag20 pyramid are correctly represented by the new ReaxFF and compared with results for gold. The simulation of self-assembled monolayers of thiolates on a silver (111) surface does not indicate the formation of staples in contrast to the results for gold-thiolate systems.</p></div></div></div>


Science ◽  
2020 ◽  
Vol 368 (6491) ◽  
pp. 642-648 ◽  
Author(s):  
Wenfeng Jiang ◽  
Zhi-bei Qu ◽  
Prashant Kumar ◽  
Drew Vecchio ◽  
Yuefei Wang ◽  
...  

The structural complexity of composite biomaterials and biomineralized particles arises from the hierarchical ordering of inorganic building blocks over multiple scales. Although empirical observations of complex nanoassemblies are abundant, the physicochemical mechanisms leading to their geometrical complexity are still puzzling, especially for nonuniformly sized components. We report the self-assembly of hierarchically organized particles (HOPs) from polydisperse gold thiolate nanoplatelets with cysteine surface ligands. Graph theory methods indicate that these HOPs, which feature twisted spikes and other morphologies, display higher complexity than their biological counterparts. Their intricate organization emerges from competing chirality-dependent assembly restrictions that render assembly pathways primarily dependent on nanoparticle symmetry rather than size. These findings and HOP phase diagrams open a pathway to a large family of colloids with complex architectures and unusual chiroptical and chemical properties.


2020 ◽  
Author(s):  
Dylan Suvlu ◽  
Mohsen Farshad ◽  
Jayendran C. Rasaiah

We describe a model of nanocluster formation that incorporates competition between ligand adsorption and nanocluster growth. Growth occurs through the addition of a metal-ligand complex and coalescence of nanoclusters. The competition between ligands for binding sites on the nanoclusters and growth of the nanoclusters through coalescence creates interesting growth pathways. The patterns are reminiscent of those observed in the synthesis of gold thiolate nanoclusters. For a particular set of rate coefficients, described herein, we observe the formation of a kinetically stable nanocluster that participates in coalescent growth. This determines the size interval of the resulting nanoclusters in the size distribution. The kinetically stable cluster can be tuned by modifying the functional form of the number of surface sites on the nanoclusters, thereby changing the growth pathway and the final sizes of the clusters.


2020 ◽  
Author(s):  
Dylan Suvlu ◽  
Mohsen Farshad ◽  
Jayendran C. Rasaiah

We describe a model of nanocluster formation that incorporates competition between ligand adsorption and nanocluster growth. Growth occurs through the addition of a metal-ligand complex and coalescence of nanoclusters. The competition between ligands for binding sites on the nanoclusters and growth of the nanoclusters through coalescence creates interesting growth pathways. The patterns are reminiscent of those observed in the synthesis of gold thiolate nanoclusters. For a particular set of rate coefficients, described herein, we observe the formation of a kinetically stable nanocluster that participates in coalescent growth. This determines the size interval of the resulting nanoclusters in the size distribution. The kinetically stable cluster can be tuned by modifying the functional form of the number of surface sites on the nanoclusters, thereby changing the growth pathway and the final sizes of the clusters.


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