Improved activity for the oxygen evolution reaction using a tiara-like thiolate-protected nickel nanocluster

Selective synthesis of the missing tiara-like Ni10, Ni5 and Ni6 thiolates by the C-S bond cleavage of bis(thioether) molecules with a DFT study

A series of new bis(phenylthioether) and bis(benzylthioether) compounds (L1-L5) having hexahydropyrimidine, imidazolidine and dihydroperimidine backbones were synthesized. Instead of giving NHC complexes, these compounds undergo facile C-S bond cleavages upon treatment with Ni(II) salts to selectively give new toroidal Ni(II) thiolates: [Ni10(SPh)20] (1) and [Ni5(SCH2Ph)10] (5), and the known [Ni6(SCH2Ph)12] (8), as confirmed by single crystal X-ray diffraction studies. By-products such as RSSR (R = Ph and CH2Ph) and partially C-S bond cleaved starting compounds were isolated or detected as well from these reactions. The C-S bond cleavage does not take place with L5 having the dihydroperimidine backbone and a plausible mechanism is proposed based on by-products isolated or detected. DFT calculations give insights into the electronic structures of these ring systems and the nature of bonding with which a dichloromethane is present inside the cavity of 1. Experimentally observed absorption spectra of 1, 5 and 8 match with the calculated spectra.

A homologous series of macrocyclic Ni clusters: synthesis, structures, and catalytic properties

Due to their intriguing ring structures and promising applications, nickel-thiolate clusters, such as [Nin(SR)2n] (n = 4-6), have attracted tremendous interest. However, investigation of the synthesis, structures, and properties of macrocyclic Nin clusters (n > 8) has been seriously impeded. In this work, a homologous series of macrocyclic nickel clusters, Nin(4MPT)2n (n = 9-12), was fabricated by using 4-methylphenthiophenol (4MPT) as the ligand. The structures and compositions of the clusters were determined by single-crystal X-ray diffraction (SXRD) in combination with electrospray ionization mass spectrometry (ESI-MS). Experimental results and theoretical calculations show that the electronic structures of the clusters do not change significantly with the increase of Ni atoms. The coordination interactions between Ni and S atoms in [NiS4] subunits are proved to play a crucial rule in the remarkable stability of Ni clusters. Finally, these clusters display excellent catalytic activity towards the reduction of p-nitrophenol, and a linear correlation between catalytic activity and ring size was revealed. The study provides a facile approach to macrocyclic homoleptic nickel clusters, and contributes to an in-depth understanding of the structure-property correlations of nickel clusters at the atomic level.

Tiara-like Hexanuclear Nickel-Platinum Alloy Nanocluster

Tiara-like metal nanoclusters (TNCs) have attracted a great deal of attention because of their high stability and easy synthesis under atmospheric conditions as well as their high activity in various catalytic reactions. Alloying is one of the methods that can be used to control the physicochemical properties of nanoclusters, but few studies have reported on alloy TNCs. In this study, we synthesized alloy TNCs [NixPt6-x(PET)12, where x = 1-5 and PET = 2-phenylethanethiolate] consisting of thiolate, nickel (Ni), and platinum (Pt). We further evaluated the stability, geometric structure, and electronic structure by high-performance liquid chromatography and density functional theory calculations. The results revealed that NixPt6-x(PET)12 has a distorted structure and is therefore less stable than single-metal TNCs.

Large-scale synthesis, mechanism, and application of a luminescent copper hydride nanocluster

Elucidating the structure-property relationships of ultra-small metal nanocluster with basic nuclear is of great significance for understanding the evolution mechanism in both the structures and properties of polynuclear metal nanoclusters. In this study, an ultra-small copper hydride (CuH for short) nanocluster was simply synthesized with high yield, and the large-scale preparation was also achieved. Single crystal X-ray diffractometer (SC-XRD) analysis shows that this copper NC contains a tetrahedral Cu4 core co-capped by four PPh2Py ligands and two Cl in which the existence of the central H atom in tetrahedron was further identified experimentally and theoretically. This CuH nanocluster exhibits bright yellow emission, which is proved to be the mixture of phosphorescence and fluorescence by the sensitivity of both emission intensity and lifetime to O2. Furthermore, the temperature-dependent emission spectra and density functional theory (DFT) calculations suggest that the luminescence of CuH mainly originates from the metal-to-ligand charge transfer and cluster-centered triplet excited states. This work offers new insights into understanding the structure-property relationship of basic nuclear CuH nanocluster.

Elucidation of the electronic structures of thiolate-protected gold nanoclusters by electrochemical measurements

Metal nanoclusters (NCs) with sizes of approximately 2 nm or less have different physical/chemical properties from those of the bulk metals owing to quantum size effects. Metal NCs, which can be size-controlled and heterometal doped at atomic accuracy, are expected to be the next generation of important materials, and new metal NCs are reported regularly. However, compared with conventional materials such as metal complexes and relatively large metal nanoparticles (>2 nm), these metal NCs are still underdeveloped in terms of evaluation and establishment of application methods. Electrochemical measurements are one of the most widely used methods for synthesis, application, and characterisation of metal NCs. This review summarizes the basic knowledge of the electrochemistry and experimental techniques, and provides examples of the reported electronic states of thiolate-protected gold NCs elucidated by electrochemical approaches. It is expected that this review will provide useful information for researchers starting to study metal NCs.