Tailoring the subshell and electronic structure of an atomically precise AuAg alloy nanocluster.

Manipulating the atomic-level structure of the subshell of a nanocluster while preserving the inner and outer shell structure is challenging. We present the synthesis and molecular structure of an alkynyl-protected Au34Ag27 nanocluster, which exhibits distinct third shell atomic arrangement, electronic structure, and optical properties from those of the Au34Ag28 nanocluster.

Nanocluster Surface Microenvironment Modulates Electrocatalytic CO2 Reduction.

The catalytic activity and product selectivity of the electrochemical CO2 reduction reaction (eCO2RR) depend strongly on the local microenvironment of mass diffusion at the nanostructured catalyst and electrolyte interface. Achieving a molecular-level understanding of the electrocatalytic reaction requires the development of tunable metal-ligand interfacial structures with atomic precision, which is highly challenging. Here, the synthesis and molecular structure of a 25-atom silver nanocluster interfaced with an organic shell comprising 18 thiolate ligands are presented. The locally induced hydrophobicity by bulky alkyl functionality near the surface of the Ag25 cluster dramatically enhances the eCO2RR activity (CO Faradaic efficiency, FECO: 90.3%) with higher CO partial current density (jCO) in an H-cell compared to Ag25 cluster (FECO: 66.6%) with confined hydrophilicity, which modulates surface interactions with water and CO2. Remarkably, the hydrophobic Ag25 cluster exhibits jCO as high as -240 mA cm-2 with FECO >90% at -3.4 V cell potential in a gas-fed membrane electrode assembly device. Furthermore, this cluster demonstrates stable eCO2RR over 120 h. Operando surface-enhanced infrared absorption spectroscopy and theoretical simulations reveal how the ligands alter the neighboring water structure and *CO intermediates, impacting the intrinsic eCO2RR activity, which provides atomistic mechanistic insights into the crucial role of confined hydrophobicity.

Copper Doping Boosts Electrocatalytic CO2 Reduction of Atomically Precise Gold Nanoclusters.

Unraveling the atomistic synergistic effects of nanoalloys on the electrocatalytic CO2 reduction reaction (eCO2RR), especially in the presence of copper, is of paramount importance. However, this endeavor encounters significant challenges due to the lack of the crystallographically determined atomic-level structure of appropriate monometallic and bimetallic analogues. Herein, we report a one-pot synthesis and structure characterization of a AuCu nanoalloy cluster catalyst, [Au15Cu4(DPPM)6Cl4(C≡CR)1]2+ (denoted as Au15Cu4). Single-crystal X-ray diffraction analysis reveals that Au15Cu4 comprises two interpenetrating incomplete, centered icosahedra (Au9Cu2 and Au8Cu3) and is protected by six DPPM, four halide, and one alkynyl ligand. The Au15Cu4 cluster and its closest monometal structural analogue, [Au18(DPPM)6Br4]2+ (denoted as Au18), as model systems, enable the elucidation of the atomistic synergistic effects of Au and Cu on eCO2RR. The results reveal that Au15Cu4 is an excellent eCO2RR catalyst in a gas diffusion electrode-based membrane electrode assembly (MEA) cell, exhibiting a high CO Faradaic efficiency (FECO) of >90%, and this efficiency is substantially higher than that of the undoped Au18 (FECO: 60% at -3.75 V). Au15Cu4 exhibits an industrial-level CO partial current density of up to -413 mA/cm2 at -3.75 V with the gas CO2-fed MEA, which is 2-fold higher than that of Au18. The density functional theory (DFT) calculations demonstrate that the synergistic effects are induced by Cu doping, where the exposed pair of AuCu dual sites was suggested for launching the eCO2RR process. Besides, DFT simulations reveal that these special dual sites synergistically coordinate a moderate shift in the d-state, thus enhancing its overall catalytic performance.

-SR removal or -R removal? A mechanistic revisit on the puzzle of ligand etching of Au25(SR)18 nanoclusters during electrocatalysis.

Accurate identification of active sites is highly desirable for elucidation of the reaction mechanism and development of efficient catalysts. Despite the promising catalytic performance of thiolated metal nanoclusters (NCs), their actual catalytic sites remain elusive. Traditional first-principles calculations and experimental observations suggested dealkylated S and dethiolated metal, respectively, to be the active centers. However, the real kinetic origin of thiolate etching during the electrocatalysis of NCs is still puzzling. Herein, we conducted advanced first-principles calculations and electrochemical/spectroscopic experiments to unravel the electrochemical etching kinetics of thiolate ligands in prototype Au25(SCH3)18 NC. The electrochemical processes are revealed to be spontaneously facilitated by dethiolation (i.e., desorption of -SCH3), forming the free HSCH3 molecule after explicitly including the solvent effect and electrode potential. Thus, exposed under-coordinated Au atoms, rather than the S atoms, serve as the real catalytic sites. The thermodynamically preferred Au-S bond cleavage arises from the selective attack of H from proton/H2O on the S atom under suitable electrochemical bias due to the spatial accessibility and the presence of S lone pair electrons. Decrease of reduction potential promotes the proton attack on S and significantly accelerates the kinetics of Au-S bond breakage irrespective of the pH of the medium. Our theoretical results are further verified by the experimental electrochemical and spectroscopic data. At more negative electrode potentials, the number of -SR ligands decreased with concomitant increase of the vibrational intensity of S-H bonds. These findings together clarify the atomic-level activation mechanism on the surface of Au25(SR)18 NCs.

Synthesis, Assembly, and Applications of Magic-Sized Semiconductor (CdSe)13 Cluster.

ConspectusAtomically precise metal chalcogenide clusters (MCCs) are model molecular compounds of scientifically and technologically important semiconductor nanocrystals, which are known as quantum dots (QDs). The significantly high ambient stability of MCCs of particular sizes, as compared to that of slightly smaller or larger sizes, made them be termed "magic-sized clusters" (MSCs). In other words, MSCs with specific sizes between sizes of precursors (typically, metal-ligand complexes) and nanocrystals (typically, QDs) appear sequentially during the colloidal synthesis of nanocrystals, while the other cluster species decompose to precursor monomers or are consumed during the growth of the nanocrystals. Unlike nanocrystals with an ambiguous atomic-level structure and a substantial size distribution, MSCs possess atomically monodisperse size, composition, and distinct atomic arrangement. Chemical synthesis and exploration of properties of MSCs are of great significance since they help systematically understand the evolution of fundamental properties as well as build structure-activity relationships at distinct molecular levels. Furthermore, MSCs are anticipated to offer atomic-level insights into the growth mechanism of the semiconductor nanocrystals, which is highly desirable in the design of advanced materials with new functions. In this Account, we cover our recent efforts in the advancement of one of the most important stoichiometric CdSe MSCs, (CdSe)13. In particular, we present its molecular structure derived from a single crystal X-ray crystallographic study of the closest MSC, Cd14Se13. The crystal structure of MSC enables not only the understanding of the electronic structure and prediction of the potential sites for heteroatom dopants (e.g., Mn2+ and Co2+) but also the identification of favorable synthetic conditions for the selective synthesis of desired MSCs. Next, we focus on enhancing the photoluminescence quantum yield and stability of Mn2+ doped (CdSe)13 MSCs through their self-assembly, which is facilitated by the rigid diamines. In addition, we show how atomic-level synergistic effects and functional groups of the assemblies of alloy MSCs can be utilized for a highly enhanced catalytic CO2 fixation with epoxides. Benefiting from the intermediate stability, the MSCs are explored as single-source precursors to low-dimensional nanostructures, such as nanoribbons and nanoplatelets, through the controlled transformation. Distinct differences in the outcome of the solid-state and colloidal-state conversion of MSCs suggest the need for careful consideration of the phase and reactivity of MSCs as well as the type of dopant to achieve novel structured multicomponent semiconductors. Finally, we summarize the Account and provide future perspectives on the fundamental and applied scientific research of MSCs.

Atom-Precise Heteroatom Core-Tailoring of Nanoclusters for Enhanced Solar Hydrogen Generation.

While core-shell nanomaterials are highly desirable for realizing enhanced optical and catalytic properties, their synthesis with atomic-level control is challenging. Here, the synthesis and crystal structure of [Au12 Ag32 (SePh)30 ]4- , the first example of selenolated Au-Ag core-shell nanoclusters, comprising a gold icosahedron core trapped in a silver dodecahedron, which is protected by an Ag12 (SePh)30 shell, is presented. The gold core strongly modifies the overall electronic structure and induces synergistic effects, resulting in high enhancements in the stability and near-infrared-II photoluminescence. The Au12 Ag32 and its homometal analog Ag44 , show strong interactions with oxygen vacancies of TiO2 , facilitating the interfacial charge transfer for photocatalysis. Indeed, the Au12 Ag32 /TiO2 exhibits remarkable solar H2 production (6810 µmol g-1  h-1 ), which is ≈6.2 and ≈37.8 times higher than that of Ag44 /TiO2 and TiO2 , respectively. Good stability and recyclability with minimal catalytic activity loss are additional features of Au12 Ag32 /TiO2 . The experimental and computational results reveal that the Au12 Ag32 acts as an efficient cocatalyst by possessing a favorable electronic structure that aligns well with the TiO2 bands for the enhanced separation of photoinduced charge carriers due to the relatively negatively charged Au12 core. These atomistic insights will motivate uncovering of the structure-catalytic activity relationships of other nanoclusters.

Alkynyl-Protected Chiral Bimetallic Ag22 Cu7 Superatom with Multiple Chirality Origins.

Understanding the origin of chirality in the nanostructured materials is essential for chiroptical and catalytic applications. Here we report a chiral AgCu superatomic cluster, [Ag22 Cu7 (C≡CR)16 (PPh3 )5 Cl6 ](PPh4 ), Ag22 Cu7 , protected by an achiral alkynyl ligand (HC≡CR: 3,5-bis(trifluoromethyl)phenylacetylene). Its crystal structure comprises a rare interpenetrating biicosahedral Ag17 Cu2 core, which is stabilized by four different types of motifs: one Cu(C≡CR)2 , four -C≡CR, two chlorides and one helical Ag5 Cu4 (C≡CR)10 (PPh3 )5 Cl4 . Structural analysis reveals that Ag22 Cu7 exhibits multiple chirality origins, including the metal core, the metal-ligand interface and the ligand layer. Furthermore, the circular dichroism spectra of R/S-Ag22 Cu7 are obtained by employing appropriate chiral molecules as optical enrichment agents. DFT calculations show that Ag22 Cu7 is an eight-electron superatom, confirm that the cluster is chirally active, and help to analyze the origins of the circular dichroism.

Body-Centered-Cubic-Kernelled Ag15Cu6 Nanocluster with Alkynyl Protection: Synthesis, Total Structure, and CO2 Electroreduction.

While atomically monodisperse nanostructured materials are highly desirable to unravel the size- and structure-catalysis relationships, their controlled synthesis and the atomic-level structure determination pose challenges. Particularly, copper-containing atomically precise alloy nanoclusters are potential catalyst candidates for the electrochemical CO2 reduction reaction (eCO2RR) due to high abundance and tunable catalytic activity of copper. Herein, we report the synthesis and total structure of an alkynyl-protected 21-atom AgCu alloy nanocluster [Ag15Cu6(C≡CR)18(DPPE)2]-, denoted as Ag15Cu6 (HC≡CR: 3,5-bis(trifluoromethyl)phenylacetylene; DPPE: 1,2-bis(diphenylphosphino)ethane). The single-crystal X-ray diffraction reveals that Ag15Cu6 consists of an Ag11Cu4 metal core exhibiting a body-centered cubic (bcc) structure, which is capped by 2 Cu atoms, 2 Ag2DPPE motifs, and 18 alkynyl ligands. Interestingly, the Ag15Cu6 cluster exhibits excellent catalytic activity for eCO2RR with a CO faradaic efficiency (FECO) of 91.3% at -0.81 V (vs the reversible hydrogen electrode, RHE), which is much higher than that (FECO: 48.5% at -0.89 V vs RHE) of Ag9Cu6 with bcc structure. Furthermore, Ag15Cu6 shows superior stability with no significant decay in the current density and FECO during a long-term operation of 145 h. Density functional theory calculations reveal that the de-ligated Ag15Cu6 cluster can expose more space at the pair of AgCu dual metals as the efficient active sites for CO formation.

Solvent Gaming Chemistry to Control the Quality of Halide Perovskite Thin Films for Photovoltaics.

Research on solvent chemistry, particularly for halide perovskite intermediates, has been advancing the development of perovskite solar cells (PSCs) toward commercial applications. A predictive understanding of solvent effects on the perovskite formation is thus essential. This work systematically discloses the relationship among the basicity of solvents, solvent-contained intermediate structures, and intermediate-to-perovskite α-FAPbI3 evolutions. Depending on their basicity, solvents exhibit their own favorite bonding selection with FA+ or Pb2+ cations by forming either hydrogen bonds or coordination bonds, resulting in two different kinds of intermediate structures. While both intermediates can be evolved into α-FAPbI3 below the δ-to-α thermodynamic temperature, the hydrogen-bond-favorable kind could form defect-less α-FAPbI3 via sidestepping the break of strong coordination bonds. The disclosed solvent gaming mechanism guides the solvent selection for fabricating high-quality perovskite films and thus high-performance PSCs and modules.

Cu28H20: a peculiar chiral nanocluster with an exposed Cu atom and 13 surface hydrides.

Reported herein is a racemate of a chiral nanocluster [Cu28H20(S2P(OiPr)2)9]-, which has a tetrahedral Cu4 core embedded in a peculiar Cu24 shell. The Cu28H20 framework conforms to idealized C3 symmetry. The positions of the hydrides were determined by a combinatorial use of 2H NMR and SC-XRD, revealing four different coordination modes: face-capping µ3-H, butterfly µ4'-H, tetrahedral µ4-H, and square-pyramidal µ5-H. These coordination modes were authenticated by DFT calculations. Simple empirical rules were developed for assigning the H NMR spectra. One exposed Cu atom from the Cu4 core and 13 exposed surface hydrides are easily accessible and thus may have catalytic functions.

High photoluminescence from self-assembled Ag2Cl2(dppe)2 clusters through metallophilic interactions.

Ligand protected metal nanoclusters (NCs) are an emerging class of functional materials with intriguing photophysical and chemical properties. The size and molecular structure play an important role in endowing NCs with characteristic optical and electronic properties. Modulation of these properties through the chemical reactivity of NCs is largely unexplored. Here, we report on the synthesis of self-assembled Ag2Cl2(dppe)2 clusters through the ligand-exchange-induced transformation of [Pt2Ag23Cl7(PPh3)10] NCs [(dppe): 1,2-bis(diphenylphosphino)ethane; (PPh3): triphenylphosphine]. The single crystal x-ray structure reveals that two Ag atoms are bridged by one dppe and two Cl ligands, forming a Ag2Cl2(dppe) cluster, which is subsequently self-assembled through dppe ligands to form [Ag2Cl2(dppe)2]n. Importantly, the Ag2Cl2(dppe)2 cluster assembly exhibits high photoluminescence quantum yield: ∼18%, which is attributed to the metallophilic interactions and rigidification of the ligand shell. We hope that this work will motivate the exploitation of the chemical reactivity of NCs as a new path to attain cluster assemblies endowed with enhanced photophysical properties.

[Pt2Cu34(PET)22Cl4]2-: An Atomically Precise, 10-Electron PtCu Bimetal Nanocluster with a Direct Pt-Pt Bond.

Heteroatom-doped metal nanoclusters (NCs) are highly desirable to gain fundamental insights into the effect of doping on the electronic structure and catalytic properties. Unfortunately, their controlled synthesis is highly challenging when the metal atomic sizes are largely different (e.g., Cu and Pt). Here, we design a metal-exchange strategy that enables simultaneous doping and resizing of NCs. Specifically, [Pt2Cu34(PET)22Cl4]2- NC, the first example of a Pt-doped Cu NC, is synthesized by utilizing the unique reactivity of [Cu32(PET)24Cl2H8]2- NC with Pt4+ ions. The single-crystal X-ray structure reveals that two directly bonded Pt atoms occupy the two centers of an unusually interpenetrating, incomplete biicosahedron core (Pt2Cu18), which is stabilized by a Cu16(PET)22Cl4 shell. The molecular structure and composition of the NC are validated by combined experimental and theoretical results. Electronic structure calculations, using the density functional theory, show that the Pt2Cu34 NC is a 10-electron superatom. The computed absorption spectrum matches well with the measured data and allows for assignment of the absorption peaks. The calculations also rationalize energetics for ligand exchange observed in the mass spectrometry data. The synergistic effects induced by Pt doping are found to enhance the catalytic activity of Cu NCs by ∼300-fold in silane to silanol conversion under mild conditions. Furthermore, our synthetic strategy has potential to produce Ni-, Pd-, and Au-doped Cu NCs, which will open new avenues to uncover their molecular structures and catalytic properties.

Assembly of Chiral Cluster-Based Metal-Organic Frameworks and the Chirality Memory Effect during their Disassembly.

Many metal clusters are intrinsically chiral but are often synthesized as a racemic mixture. By taking chiral Ag14(SPh(CF3)2)12(PPh3)4(DMF)4 (Ag14) clusters with bulky thiolate ligands as an example, we demonstrate herein an interesting assembly disassembly (ASDS) strategy to obtain the corresponding, optically pure crystals of both homochiral enantiomers, R-Ag14m and S-Ag14m. The ASDS strategy makes use of two bidentate linkers with different chiral configurations, namely, (1R,2R,N1E,N2E)-N1,N2-bis(pyridin-3-ylmethylene)cyclohexane-1,2-diamine (LR) and the corresponding chiral analogue LS. For comparison, we also use the racemic mixture of equimolar of LR and LS (LRS). Three three-dimensional (3D) Ag14-based metal-organic frameworks (MOFs) were characterized by X-ray crystallography to be [Ag14(SPh(CF3)2)12(PPh3)4(LR)2]n (Ag14-LR), [Ag14(SPh(CF3)2)12(PPh3)4(LS)2]n (Ag14-LS), and [Ag14(SPh(CF3)2)12(PPh3)4(LRS)2]n (Ag14-LRS), respectively. As expected, the building blocks in Ag14-LR or Ag14-LS are homochiral R-Ag14 or S-Ag14, respectively. In contrast, Ag14-LRS is achiral and crystallizes with a diamond-like structure containing alternate R-Ag14 and S-Ag14 clusters. During the assembly process, the racemic Ag14 clusters were converted to homochiral building blocks, namely, R-Ag14 for Ag14-LR and S-Ag14 for Ag14-LS. Subsequently, the chiral linkers were removed from the crystals of Ag14-LR and Ag14-LS via hydrolysis with water, and from the disassembled solid material Ag14-DR and Ag14-DS, optically pure enantiomers R-Ag14m and S-Ag14m were obtained. It is hoped that this simple assembly strategy can be used to construct cluster-based chiral assemblage materials and that the subsequent disassembly protocol can be used to obtain optically pure chiral cluster molecules from as-prepared racemic mixtures.

Enhanced Surface Ligands Reactivity of Metal Clusters by Bulky Ligands for Controlling Optical and Chiral Properties.

Surface ligands play critical roles in determining the surface properties of metal clusters. However, modulating the properties and controlling the surface structure of clusters through surface-capping-agent displacement is challenging. Herein, [Ag14 (SPh(CF3 )2 )12 (PPh3 )4 (DMF)4 ] (Ag14 -DMF; DMF=N,N-dimethylformamide), with weakly coordinated DMF ligands on surface silver sites, was synthesized by a mixed-ligands strategy. Owing to the high surface reactivity of Ag14 -DMF, the surface ligands are labile, easily dissociated or exchanged by other ligands. Based on the enhanced surface reactivity, easy modulation of the optical properties of Ag14 by reversible "on-off" DMF ligation was realized. When chiral amines were introduced to as-prepared products, all eight surface ligands were replaced by amines and the racemic Ag14 clusters were converted to optically pure homochiral Ag14 clusters as evidenced by circular dichroism (CD) activity and single-crystal X-ray diffraction (SCXRD). This work provides a new insight into modulation of the optical properties of metal clusters and atomically precise homochiral clusters for specific applications are obtained.

Atomically Precise Alkynyl- and Halide-Protected AuAg Nanoclusters Au78Ag66(C≡CPh)48Cl8 and Au74Ag60(C≡CPh)40Br12: The Ligation Effects of Halides.

Reported herein are the synthesis and structures of two high-nuclearity AuAg nanoclusters, namely, [Au78Ag66(C≡CPh)48Cl8]q- and [Au74Ag60(C≡CPh)40Br12]2-. Both clusters possess a three-concentric-shell Au12@Au42@Ag60 structure. However, the dispositions of the metal atoms, and the ligand coordination modes, of the outermost shells of these clusters are distinctly different. These structural differences reflect the bonding characteristics of the halide ligands. As revealed by density functional theory analysis, these clusters exhibit superatomic electron shell closings at magic numbers of 92 (for q = 4) and 84, respectively, consistent with their spherical shapes. Both clusters exhibit unusual multivalent redox properties.

Ag44 (EBT)26 (TPP)4 Nanoclusters With Tailored Molecular and Electronic Structure.

Although atomically precise metalloid nanoclusters (NCs) of identical size with distinctly different molecular structures are highly desirable to understand the structural effects on the optical and photophysical properties, their synthesis remains highly challenging. Herein, we employed phosphine and thiol capping ligands featuring appropriate steric effects and synthesized a charge-neutral Ag NC with the formula Ag44 (EBT)26 (TPP)4 (EBT: 2-ethylbenzenethiolate; TPP: triphenylphosphine). The single-crystal X-ray structure reveals that this NC has a hollow metal core of Ag12 @Ag20 and a metal-ligand shell of Ag12 (EBT)26 (TPP)4 . The presence of mixed ligands and long V-shaped metal-ligand motifs on this NC has resulted in an enhancement of the NIR-II photoluminescence quantum yield by >25-fold compared to an all-thiolate-stabilized anionic [Ag44 (SR)30 ]4- NC (SR: thiolate). Time-dependent density-functional calculations show that our Ag44 NC is an 18-electron superatom with a modulated electronic structure as compared to the [Ag44 (SR)30 ]4- anion, significantly influencing its optical properties.

[Cu32(PET)24H8Cl2](PPh4)2: A Copper Hydride Nanocluster with a Bisquare Antiprismatic Core.

Atomically precise coinage metal (Au, Ag, and Cu) nanoclusters (NCs) have been the subject of immense interest for their intriguing structural, photophysical, and catalytic properties. However, the synthesis of Cu NCs is highly challenging because of low reduction potential and high reactivity of copper, demonstrating the need for new synthetic methods using appropriate ligand combinations. By designing a diamine-assisted synthetic strategy, here we report the synthesis and total structure characterization of a box-like dianionic Cu NC [Cu32(PET)24H8Cl2](PPh4)2 coprotected by 2-phenylethanethiolate (PET), hydride, and chloride ligands. Its crystal structure comprises a rare bisquare antiprismatic Cu14H8 core, assembled by two square antiprisms by edge sharing, followed by hydride binding. The rod-shaped Cu14H8 core is clamped by two complex Cu7(PET)11Cl and two simple Cu2PET metal ligand frameworks, constructing the complete structure of Cu32 NC. The presence, number, and location of hydrides are established by combined experimental and density functional theory results. The electronic structure calculations show the cluster as a zero-free-electron system, reproduce well the measured optical absorption spectrum, and explain the main absorption features. Furthermore, the Cu32 cluster is found to be a highly active homogeneous catalyst for C-N bond formation in aniline carbonylation reactions at room temperature. We hope that new findings in this work will stimulate and expand the research on Cu and other active metal NCs.

Methylamine-Dimer-Induced Phase Transition toward MAPbI3 Films and High-Efficiency Perovskite Solar Modules.

Perovskite films prepared with CH3NH2 molecules under ambient conditions have led to rapid fabrication of perovskite solar cells (PSCs), but there remains a lack of mechanistic studies and inconsistencies with operability in their production. Here the crystal structure of CH3NH2-CH3NH3PbI3 was analyzed to involve hydrogen bonds (CH3NH2···CH3NH3+) and has guided the facile, reproducible preparation of high-quality perovskite films under ambient conditions. Hydrogen bonds within CH3NH2···CH3NH3+ dimers were found in the CH3NH2-CH3NH3PbI3 intermediates, accompanied by 1D-PbI3- chains (δ-phase). The weakly hydrogen-bonded CH3NH2 molecules were easily released from the CH3NH2-CH3NH3PbI3 intermediates, contributing to rapid, spontaneous phase transition from 1D-PbI3- (δ-phase) to 3D-PbI3- (α-phase). Further introduction of CH3NH3Cl into the CH3NH2-CH3NH3PbI3 intermediates led to interruption of 1D-PbI3- transition into 0D-Pb2I9-xClx5-(0 < x < 6), adjusting the phase transition route toward 3D-PbI3-. On the basis of the above understanding, CH3NH2 solution in ethanol and CH3NH3Cl were used for precursors and a best efficiency of 20.3% in PSCs was achieved. Large-scale modules (12 cm2 aperture area) fabricated by a dip-coating technology exhibited an efficiency up to 16.0% and outstanding stability over 10 000 s under continuous output. The developed preparation method of perovskite precursors and insightful research into the methylamine-dimer-induced phase transition mechanism have enabled the production of high-quality perovskite films with robust operability, showing great potential for large-scale commercialization.

Generation of Donor/Donor Copper Carbenes through Copper-Catalyzed Diyne Cyclization: Enantioselective and Divergent Synthesis of Chiral Polycyclic Pyrroles.

The generation of metal carbenes from readily available alkynes represents a significant advance in metal carbene chemistry. However, most of these transformations are based on the use of noble-metal catalysts and successful examples of such an asymmetric version are still very scarce. Here a copper-catalyzed enantioselective cascade cyclization of N-propargyl ynamides is reported, enabling the practical and atom-economical construction of diverse chiral polycyclic pyrroles in generally good to excellent yields with wide substrate scope and excellent enantioselectivities (up to 97:3 e.r.). Importantly, this protocol represents the first copper-catalyzed asymmetric diyne cyclization. Moreover, mechanistic studies revealed that the generation of donor/donor copper carbenes is presumably involved in this 1,5-diyne cyclization, which is distinctively different from the related gold catalysis, and thus it constitutes a novel way for the generation of donor/donor metal carbenes.

Highly Robust but Surface-Active: An N-Heterocyclic Carbene-Stabilized Au25 Nanocluster.

Surface organic ligands play a critical role in stabilizing atomically precise metal nanoclusters in solutions. However, it is still challenging to prepare highly robust ligated metal nanoclusters that are surface-active for liquid-phase catalysis without any pre-treatment. Now, an N-heterocyclic carbene-stabilized Au25 nanocluster with high thermal and air stabilities is presented as a homogenous catalyst for cycloisomerization of alkynyl amines to indoles. The nanocluster, characterized as [Au25 (i Pr2 -bimy)10 Br7 ]2+ (i Pr2 -bimy=1,3-diisopropylbenzimidazolin-2-ylidene) (1), was synthesized by direct reduction of AuSMe2 Cl and i Pr2 -bimyAuBr with NaBH4 in one pot. X-ray crystallization analysis revealed that the cluster comprises two centered Au13 icosahedra sharing a vertex. Cluster 1 is highly stable and can survive in solution at 80 °C for 12 h, which is superior to Au25 nanoclusters passivated with phosphines or thiols. DFT computations reveal the origins of both electronic and thermal stability of 1 and point to the probable catalytic sites. This work provides new insights into the bonding capability of N-heterocyclic carbene to Au in a cluster, and offers an opportunity to probe the catalytic mechanism at the atomic level.