Bonding and Acidity of the Formal Hydride in the Prototypical Au9 (PPh3 )8 H2+ Nanocluster

The Near-Sightedness of Many-Body Interactions in Anharmonic Vibrational Couplings

Couplings between vibrational motions are driven by electronic interactions, and these couplings carry special significance in vibrational energy transfer, multidimensional spectroscopy experiments, and simulations of vibrational spectra. In this investigation, the many-body contributions to these couplings are analyzed computationally in the context of clathrate-like alkali metal cation hydrates, including Cs+(H2O)20, Rb+(H2O)20, and K+(H2O)20, using both analytic and quantum-chemistry potential energy surfaces. Although the harmonic spectra and one-dimensional anharmonic spectra depend strongly on these many-body interactions, the mode-pair couplings were, perhaps surprisingly, found to be dominated by one-body effects, even in cases of couplings to low-frequency modes that involved the motion of multiple water molecules. The origin of this effect was traced mainly to geometric distortion within water monomers and cancellation of many-body effects in differential couplings, and the effect was also shown to be agnostic to the identity of the ion. These outcomes provide new understanding of vibrational couplings and suggest the possibility of improved computational methods for the simulation of infrared and Raman spectra.

A Small-Molecule Organic Cathode with Extended Conjugation toward Enhancing Na+ Migration Kinetics for Advanced Sodium-Ion Batteries

Organic cathode materials show excellent prospects for sodium-ion batteries (SIBs) owing to their high theoretical capacity. However, the high solubility and low electrical conductivity of organic compounds result in inferior cycle stability and rate performance. Herein, an extended conjugated organic small molecule is reported that combines electroactive quinone with piperazine by the structural designability of organic materials, 2,3,7,8-tetraamino-5,10-dihydrophenazine-1,4,6,9-tetraone (TDT). Through intermolecular condensation reaction, many redox-active groups C═O and extended conjugated structures are introduced without sacrificing the specific capacity, which ensures the high capacity of the electrode and enhances rate performance. The abundant NH2 groups can form intermolecular hydrogen bonds with the C═O groups to enhance the intermolecular interactions, resulting in lower solubility and higher stability. The TDT cathode delivers a high initial capacity of 293 mAh g-1 at 500 mA g-1 and maintains 90 mAh g-1 at an extremely high current density of 70 A g-1. The TDT || Na-intercalated hard carbon (Na-HC) full cells provide an average capacity of 210 mAh g-1 during 100 cycles at 500 mA g-1 and deliver a capacity of 120 mAh g-1 at 8 A g-1.

Reduction-Oxidation Cascade Strategy for Reforming a Au13-Kerneled Gold Thiolate Nanocluster

Gold nanoclusters protected by thiolate ligands are ideal models for investigating the structure-property correlation of nanomaterals. Introducing relatively weak coordinating ligands into gold thiolate nanoclusters and thus reforming their structures is beneficial for further releasing their activities. However, controlling the selectivity of the process is a challenging task. In this work, we report a cascade strategy for deeply and purposefully reforming the structures of gold thiolate nanoclusters, exemplified by a Au13-kerneled Au23 nanocluster. Specifically, weakly coordinated triphenylphosphine was utilized to reduce (activate) the surface of Au23, enabling its further structural reformation by the following oxidation step. A structurally distinctive Au20 nanocluster was obtained based on this reduction-oxidation cascade strategy. Mechanism studies reveal that both the reduction and oxidation steps and their working sequence are critical for the transformation. Theoretical and experimental results all indicate that the deep structural reformation results in the evolution of the electronic and photoluminescent properties of the gold thiolate nanocluster.