Redox-Induced Interconversion of Two Au8 Nanoclusters: the Mechanism and the Structure-Bond Dissociation Activity Correlations.

The interconversion of atomically precise nanoclusters represents an excellent platform to understand the structural correlations of nanomaterials at the atomic level. Herein, density functional theory calculations were performed to elucidate the mechanism of the redox-induced interconversion of [Au8(dppp)4]2+ and [Au8(dppp)4Cl2]2+ (dppp is short for 1,3-bis(diphenylphosphino)propane) nanoclusters. Reduction is the driving force for the conversion of [Au8(dppp)4Cl2]2+ to [Au8(dppp)4]2+, while the Au-Au and first Au-Cl bond dissociations occur asynchronously on the two different corner Au atoms to avoid the formation of an electron-deficient Au atom. By contrast, the reduced electron density of [Au8(dppp)4]2+ by oxidation with O2 weakens the outmost Au-Au bond therein and facilitates the coordination of the electron-rich chloride(s). The reduction- and oxidation-induced activations, respectively, of Au-Cl and Au-Au bonds and the elucidated principles on the structure-activity correlations might also be generalized to other size conversions upon redox treatment.

Steric and Electrostatic Control of the pH-Regulated Interconversion of Au16(SR)12 and Au18(SR)14 (SR: Deprotonated Captopril).

An understanding of the response of nanomaterials to specific environmental parameters is an essential prerequisite for their practical use, especially in living systems. Herein, we disclose the preparation of a water-soluble nanocluster Au16(SR)12 (SR denotes deprotonated captopril) and its characterization by a combination of theoretical (e.g., density functional theory calculations) and experimental (UV-vis, electrospray ionization mass spectrometry, etc.) methods. Interestingly, Au16(SR)12 was found to convert to Au18(SR)14 under acidic conditions, while the reverse conversion from Au18(SR)14 to Au16(SR)12 occurred upon the addition of base. A mechanistic investigation determined this pH regulation to originate from the distinct steric and electrostatic properties of these two clusters. This study is the first to report the susceptibility of Au18(SR)14 and Au16(SR)12 to pH, and the distinct pH stability unambiguously reveals the importance of size-tracking of nanomaterials in living systems for future clinical applications.

Rhombicuboctahedral Ag100 : Four-Layered Octahedral Silver Nanocluster Adopting the Russian Nesting Doll Model.

Precise atomic structure of metal nanoclusters (NCs) is fundamental for elucidating the structure-property relationships and the inherent size-evolution principles. Reported here is the largest known FCC-based (FCC=face centered cubic) silver nanocluster, [Ag100 (SC6 H3 3,4 F2 )48 (PPh3 )8 ]- : the first all-octahedral symmetric nesting Ag nanocluster with a four-layered Ag6 @Ag38 @Ag48 S24 @Ag8 S24 P8 structure, consistent symmetry elements, and a unique rhombicuboctahedral morphology distinct from theoretical predictions and previously reported FCC-based Ag clusters. DFT studies revealed extensive interlayer interactions and degenerate frontier orbitals. The FCC-based Russian nesting doll model constitutes a new platform for the study of the size-evolution principles of Ag NCs.

The pivotal alkyne group in the mutual size-conversion of Au9 with Au10 nanoclusters.

Herein, density functional theory (DFT) calculations were performed to elucidate the mechanism of the reversible single atom size conversion between [Au10(DMPP)4(C6H11C[triple bond, length as m-dash]C)]3+ and [Au9(DMPP)4]3+ (DMPP is 2,2'-bis-(dimethylphosphino)-1,1'-biphenyl, the simplified, theoretical model of the experimentally used 2,2'-bis-(diphenylphosphino)-1,1'-binaphthyl). The presence of a unique alkyne group is pivotal to the nucleophilic attack of the phosphine ligand on the electron-deficient Au10 core. After that, a formal ligand exchange and facile 1,2-P (of the diphosphine ligand) transfer occur to generate the Au9 cluster product. By contrast, the absence of the alkyne group results in a relatively electron-rich Au9 core, and thus an electrophilic attack of the Au(alkyne) complex on the most electron-rich metal sites occurs first. After that, the Au(alkyne) migration on the cluster surface, 1,2-P transfer and core-reconstruction occur successively to generate the thermodynamically highly stable Au10 cluster product.

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.

Real-time visualization of autophagy by monitoring the fluctuation of lysosomal pH with a ratiometric two-photon fluorescent probe.

A benzimidazole-decorated two-photon fluorescent probe (Lyso-MPCB) based on the p-methoxyphenylacetylene-substituted carbazole was developed for detecting lysosomal pH with a double-channel signal, which can be used to visualize autophagy by real-time imaging the fluctuation of the pH in the lysosomes.