DFT Insights into the Variety in the Coordination Modes of the Equatorial Halides in [Au13 Ag12 (PR3 )10 X8 ]+ (X=Cl/Br) Clusters.

The bonding character within metal nanoclusters represents an intriguing topic, shedding light on the inherent driving force for the packing preference in nanomaterials. Herein, density functional theory (DFT) calculations were conducted to investigate the correlation of the series of isomeric [Au13 Ag12 (PR3 )10 X8 ]+ (X=Cl/Br) clusters, which are mainly differentiated by the coordination mode of the equatorial halides (µ2 -, µ3 - and µ4 -) in the rod-like, bi-icosahedral framework. The theoretical simulation corroborates the variety in the configuration of the Au13 Ag12 clusters and elucidates the fast isomerization kinetics among the different configurations. The easy tautomerization and the variety in chloride binding modes correspond to a fluxionality character of the equatorial halides and are verified by the potential energy curve analysis. The structural flexibility of the central Au3 Ag10 block is the main driving force, while the relatively stronger Ag-X bonding interaction (compared to that of Au-X), and a sufficient number of halides are also requisite for the associating Ag-X tautomerizations.

Core Charge Density Dominated Size-Conversion from Au6 P8 to Au8 P8 Cl2.

The stimulus-response of metal nanoclusters is crucial to their applications in catalysis and bio-clinics, etc. However, its mechanistic origin has not been well studied. Herein, the mechanism of the AuI PPh3 Cl-induced size-conversion from [Au6 (DPPP)4 ]2+ to [Au8 (DPPP)4 Cl2 ]2+ (DPPP is short for 1,3-bis(diphenylphosphino)propane) is theoretically investigated with density functional theory (DFT) calculations. The optimal size-growth pathway, and the key structural parameters were elucidated. The Au-P bond dissociation steps are key to the size-growth, the easiness of which was determined by the charge density of the metallic core of the cluster precursors (i.e., "core charge density"). This study sheds light on the inherent structure-reactivity relationships during the size-conversion, and will benefit the deep understanding on the kinetics of more complex systems.

The Structure-Property Correlations in the Isomerism of Au21 (SR)15 Nanoclusters by Density Functional Theory Study.

Isomerism of atomically precise noble metal nanoclusters provides an excellent platform to investigate the structure-property correlations of metal nanomaterials. In this study, we performed density functional theory (DFT) and time-dependent (TD-DFT) calculations on two Au21 (SR)15 nanoclusters, one with a hexagonal closed packed core (denoted as Au21 hcp ), and the other one with a face-centered cubic core (denoted as Au21 fcc ). The structural and electronic analysis on the typical Au-Au and Au-S bond distances, bond orders, composition of the frontier orbitals and the origin of optical absorptions shed light on the inherent correlations between these two clusters.

The Ligand-Exchange Reactions of Rod-Like Au25-n Mn (M=Au, Ag, Cu, Pd, Pt) Nanoclusters with Cysteine - A Density Functional Theory Study.

The atomic precision of ultrasmall noble-metal nanoclusters (NMNs) is fundamental for elucidating structure-property relationships and probing their practical applications. So far, the atomic structure of NMNs protected by organic ligands has been widely elucidated, whereas the precise atomic structure of NMNs protected by water-soluble ligands (such as peptides and nucleic acid), has been rarely reported. With the concept of "precision to precision", density functional theory (DFT) calculations were performed to probe the thermodynamic plausibility and inherent determinants for synthesizing atomically precise, water-soluble NMNs via the framework-maintained two-phase ligand-exchange method. A series of rod-like Au25-n Mn (M=Au, Ag, Cu, Pd, Pt) NMNs with the same framework but varied ligands and metal compositions was chosen as the modeling reactants, and cysteine was used as the modeling water-soluble ligand. It was found that the acidity of the reaction remarkably affects the thermodynamic facility of the ligand exchange reactions. Ligand effects (structural distortion and acidity) dominate the overall thermodynamic facility of the ligand-exchange reaction, while the number and type of doped metal atom(s) has little influence.

The Structure of a Au7Cu12 Bimetal Nanocluster and Its Strong Emission.

Herein, a Au-Cu bimetal nanocluster (bi-MNC) with strong emission (13.2% quantum yield) was synthesized and structurally determined. Its structure features a sandwich construction: a ring-like Au7Cu6 kernel is caught in the middle of the two "hat-like" (CuSPNC)3 motifs with four Br atoms, resulting in a formula of [Au7Cu12(dppy)6(TBBT)6Br4]3+ (dppy = PPh2Py, TBBT = SPh- t-Bu). Interestingly, structural analysis shows that the bonding (N-Cu and µ3S-Cu3) is the key factor to endow this bi-MNC with strong emission by locking the intramolecular motion of surface structure, and destroying the intramolecular π···π interactions is designed to boost emission (19.2% vs 13.2%). Furthermore, the structure-luminescence relationship is further explored by theoretical calculation. This work will provide new idea and strategy to prepare bi-MNCs with strong emission.

X-ray crystal structure and doping mechanism of bimetallic nanocluster Au36-xCux(m-MBT)24 (x = 1-3).

A novel Au36-xCux(m-MBT)24 (x = 1-3, m-MBT = 3-methylbenzenethiolate) nanocluster has been prepared. According to the X-ray single crystal diffractometer, the structure of Au36-xCux(m-MBT)24 is similar to that of Au36(SPhtBu)24. The Au36-xCux(m-MBT)24 nanocluster contains a face-centered cubic (FCC) M28 core, which is protected by 4 M2S3 (M = Au/Cu) staple motifs and 12 bridging SR ligands. The Cu dopants could possibly occupy 14 sites (six in the sub-surface and eight in the staple motifs). Spectral monitoring indicates that the number of Cu dopants sequentially increased on increasing the amount of Cu precursors (relative to a Au control). Meanwhile, DFT calculations imply that the maximum doping number of Cu is 3, and doping occurs preferentially at the staple sites and sub-surface sites (instead of the centre of the core). Because the atomic orbital of the peripheral locations hardly contributes to the frontier molecular orbitals, the UV-vis of the AuCu alloy is almost the same as that of its homometallic Au counterpart.