Because of the typical instability of copper nanoclusters, atom-precise structural elucidation of these nanoclusters has remained elusive. Herein, we report an air- and moisture-stable 23-copper nanocluster (SD/Cu23a or SD/Cu23b) isolated from the reaction of Cu­(CF3COO)2, t BuCCH, Cu powder, and Ph2SiH2 using a gradient reduction (CuII → CuI → Cu0) strategy (GRS), which is competent for controlling the kinetics of the reduction reaction, thus avoiding formation of pure CuI complexes or large Cu0 nanoparticles. The solid-state structure of the Cu23 nanocluster shows a rare [Cu4]0 tetrahedral kernel surrounded by an outer Cu19 shell, which is protected by t BuCC– and CF3COO– ligands. The Cu23nanocluster is a rare four-electron superatom with a 1S21P2 electronic shell closure and can be crystallized in two polymorphs (R3c and R3̅) depending on the solvent used. The crystallization of SD/Cu23a in the R3c space group is mainly governed by van der Waals forces and C–H···F interactions, whereas additional intermolecular C–H···Clchloroform interactions are responsible for the R3̅ space group of SD/Cu23b. This work not only shows the ingenuity of a gradient reduction strategy for the synthesis of copper nanoclusters but also provides a better fundamental understanding of how to produce the polymorphic copper nanoclusters in a precisely tunable fashion.

The noncovalent S···O bonding interaction is an evolutionary force that has been smartly exploited by nature to modulate the conformational preferences of proteins. The employment of this type of weak noncovalent force to drive chemical reactions is promising yet remains largely elusive. Herein, we describe a dual chalcogen–chalcogen bonding catalysis strategy that the distinct chalcogen atoms simultaneously interact with two chalcogen-based electron donors to give rise to the catalytic activity, thus facilitating chemical reactions. Conventional approaches to the Rauhut–Currier-type reactions require the use of strongly nucleophilic Lewis bases as essential promoters. The implementation of this dual chalcogen–chalcogen bonding catalysis strategy allows the simultaneous Se···O bonding interaction between chalcogen-bonding donors and an enone and an alcohol, enabling the realization of the Rauhut–Currier-type reactions in a distinct way. The further implementation of a consecutive dual Se···O bonding catalysis approach enables the achievement of an initial Rauhut–Currier-type reaction to give an enone product which further undergoes an alcohol-addition induced cyclization reaction. This work demonstrates that the nearly linear chalcogen-bonding interaction can differentiate similar alkyl groups to give rise to regioselectivity. Moreover, the new strategy shows its advantage as it not only enables less reactive substrates working efficiently but tolerates inaccessible substrates using conventional methods.

During the past decade, increasing attention has been paid to photoluminescent nanocarbon materials, namely, carbon quantum dots (CQDs). It is gradually accepted that surface engineering plays a key role in regulating the properties and hence the applications of the CQDs. In this paper, we prepared highly charged CQDs through a one-pot pyrolysis with citric acid as carbon source and a room-temperature imidazolium-based ionic liquid as capping agent. The as-prepared CQDs exhibit high quantum yields up to 25.1% and are stable under various environments. In addition, the amphiphilicity of the CQDs can be facilely tuned by anion exchange, which leads to a spontaneous phase transfer between water and oil phase. The promising applications of the CQDs as ion sensors and fluorescent inks have been demonstrated. In both cases, these ionic-liquid-modified CQDs were found to possess novel characteristics and/or superior functions compared to existing ones.

A modular and efficient method for the synthesis of α-substituted 1,2-dihydroquinolines is described. Under mild metal-free conditions, readily available N-carbamoyl 1,2-dihydroquinolines undergo oxidative C-H alkynylation, alkenylation, and allylation with a range of potassium trifluoroborates using TEMPO oxoammonium salt as an oxidant.

Two ultrasmall gold clusters, Au13 and Au8, were identified as a distorted Ih icosahedral Au13 and edge-shared “core + 4exo” structure Au8S2 cores, respectively. They showed interesting luminescence and electrochemical properties.