An Atomically Precise Pyrazolate-Protected Copper Nanocluster Exhibiting Exceptional Stability and Catalytic Activity

The synthesis of atomically precise copper nanoclusters (Cu-NCs) with high chemical stability is a prerequisite for practical applications, yet still remains a long-standing challenge. Herein, we have prepared a pyrazolate-protected Cu-NC ( Cu8 ), which exhibited exceptional chemical stability either in solid-state or in solution. The crystals of Cu8 are still suitable for single crystal X-ray diffraction analysis even after being treated with boiling water, 8 wt % H₂O₂, high concentrated acid (1 M HCl) or saturated base (≈20 M KOH), respectively. More importantly, the structure of Cu8 in solution also remained intact toward oxygen, organic acid (100 eq. HOAc) or base (400 eq. dibutylamine) confirmed by ¹H NMR and UV/Vis analysis. Taking advantage of high alkali-resistant, Cu8 illustrates excellent catalytic activity for the synthesis of indolizines, and it can be reused for at least 10 cycles without losing catalytic performance.     

Atomically Tailored Gold Nanoclusters for Catalytic Application

Recent advances in the synthetic chemistry of atomically precise metal nanoclusters (NCs) have significantly broadened the accessible sizes and structures. Such particles are well defined and have intriguing properties, thus, they are attractive for catalysis. Especially, those NCs with identical size but different core (or surface) structure provide unique opportunities that allow the specific role of the core and the surface to be mapped out without complication by the size effect. Herein, we summarize recent work with isomeric Au_n NCs protected by ligands and isostructural NCs but with different surface ligands. The highlighted work includes catalysis by spherical and rod‐shaped Au₂₅ (with different ligands), quasi‐isomeric Au₂₈(SR)₂₀ with different R groups, structural isomers of Au₃₈(SR)₂₄ (with identical R) and Au₃₈S₂(SR)₂₀ with body‐centred cubic (bcc) structure, and isostructural [Au₃₈L₂₀(PPh₃)₄]²⁺ (different L). These isomeric and/or isostructural NCs have provided valuable insights into the respective roles of the kernel, surface staples, and the type of ligands on catalysis. Future studies will lead to fundamental advances and development of tailor‐made catalysts.     

金团簇电催化二氧化碳还原反应的研究进展

二氧化碳电还原反应(CO₂RR)在改善能源利用方式、 实现可持续碳循环以及生产高附加值液体燃料和化学品等方面具有广阔的应用前景, 近年来受到广泛关注. 有机配体保护的金团簇具有确定的晶体结构, 其不同的尺寸、 配体及组成可以有效调控氧化还原电位, 作为一种独特的模型催化剂, 为探索原子水平的CO₂RR反应机理提供了新机遇. 本文综合评述了纯金团簇和异金属原子掺杂的金团簇催化CO₂RR的研究进展, 包括金团簇的电荷、 尺寸、 配体以及掺杂对CO₂RR性能的影响, 重点讨论了CO₂RR的反应机理, 总结了金团簇在CO₂RR中所面临的挑战, 并展望了金团簇在CO₂RR中未来的研究方向和发展前景.     

Metalla-Claisen Rearrangement in Gold-Catalyzed [4+2] Reaction: A New Elementary Reaction Suggested for Future Reaction Design

We report here computational evidence for a metalla-Claisen rearrangement (MCR) in the case of gold-catalyzed [4+2] cycloaddition reaction of yne-dienes. The [4+2] reaction starts from exo cyclopropanation, followed by MCR and reductive elimination. The cyclopropane moiety formed in the first step is crucial for a low barrier of the MCR step. In addition, the importance of an appropriate combination of the tether group and the terminal substituent on alkyne in the yne-diene substrates was studied. The mechanism of rhodium-catalyzed [4+2] reaction of yne-dienes was also investigated to see whether an MCR mechanism is involved or not. The findings and new understanding hereby reported represent an important advance in the catalysis field.     

甲烷与N_2~+反应机理的理论研究

利用量子化学理论对CH4和N2+的反应进行了理论研究,分析了反应势能面,得到了4条可能的反应通道.在所有的反应路径中,如果反应物所具有的能量较高,则路径PathP2(1),PathP2(2)和PathP3为主要反应通道,得到的产物应该是P2(CH3+N2H+)和P3(CH3++N2+H);如果反应物所具有的能量较低,则路径PathP1,PathP2(1)和PathP2(2)为主要反应通道,得到的产物应该是P1(CH4++N2)和P2(CH3+N2H+).     

Pincer ligand coordination at a triosmium cluster: X-ray structures of 1,2-Os3(CO)10[4,6-bis(diphenylphosphinomethyl)-m-xylene] and 1,2-Os3(CO)10[1-diphenylphosphino-1-{(2,4-dimethyl-5-diphenylphosphinomethyl)phenyl}-propan-2-ol]

The reaction between the triosmium cluster 1,2-Os₃(CO)₁₀(MeCN)₂ and the diphosphine pincer ligand 4,6-bis(diphenylphosphinomethyl)-m-xylene (dppx) has been examined and found to yield the pincer-bridged cluster 1,2-Os₃(CO)₁₀(dppx) (2) as the major product, in addition to the pincer-bridged cluster 1,2-Os₃(CO)₁₀[1-diphenylphosphino-1-{(2,4-dimethyl-5-diphenylphosphinomethyl)phenyl}-propan-2-ol] (3) in trace amounts (<2% yield). Both cluster products have been isolated and their molecular structures determined by crystallographic analyses. The structural highlights of compounds 2 and 3, which represent the first examples of pincer-ligated metal clusters, are discussed. The origin of the functionalized diphosphine ligand in 3 is traced to the ethanol solvent that was used in the recrystallization of the dppx ligand.     

金纳米簇-多金属氧酸盐复合物的制备及催化选择性氧化环已烯性能研究

通过4-N,N二甲基胺基吡啶和多金属氧酸负离子形成的复合载体稳定金纳米颗粒,制得金纳米簇-多金属氧酸盐的复合物.复合物的组成以及金纳米颗粒的分布状态由XPS和TEM表征.利用多金属氧酸和金纳米颗粒的相互协助作用,使得这类复合物是一种优异的低温选择性氧化催化剂.     

Poly-Hydride [AuI7(PPh3)7H5](SbF6)2 cluster complex: Structure,Transformation, and Electrocatalytic CO2 Reduction Properties

Hydride Au^I bonds are labile due to the mismatch in electric potential of an oxidizing metal and reducing ligand, and therefore the structure and structure–activity relationships of nanoclusters that contain them are seldom studied. Herein, we report the synthesis and characterization of [Au₇(PPh₃)₇H₅](SbF₆)₂ (abbrev. Au₇H₅ ²⁺ ), an Au cluster complex containing five hydride ligands, which decomposed to give [Au₈(PPh₃)₇]²⁺ (abbrev. Au₈ ²⁺ ) upon exposure to light (300 to 450 nm). The valence state of Au^I and H⁻ was verified by density functional theory (DFT) calculations, NMR, UV/Vis and XPS. The two nanoclusters behaved differently in the electrocatalytic CO₂ reduction reaction (CO₂RR): Au₇H₅ ²⁺ exhibited 98.2 % selectivity for H₂, whereas Au₈ ²⁺ was selective for CO (73.5 %). Further DFT calculations showed that the H⁻ ligand inhibited the CO₂RR process compared with the electron-donor H.     

Ternary Rare Earth (RE) Gold Compounds REAuCd and RE2Au2Cd

New intermetallic rare earth compounds REAuCd (RE = Y, La–Nd, Sm–Yb) and RE₂Au₂Cd (RE = La, Pr, Nd, Sm) were prepared by reaction of the elements in sealed tantalum tubes in a high‐frequency furnace. The compounds were investigated by X‐ray diffraction both on powders and single crystals. The equiatomic REAuCd compounds with RE = Y, La–Nd, Sm, and Gd–Tm adopt the ZrNiAl type structure with space group P62m. Single crystal X‐ray data yielded a = 786.2(2), c = 415.9(1) pm, wR2 = 0.0337, 402 F² values for LaAuCd and a = 782.91(9), c = 410.01(5) pm, wR2 = 0.0653, 395 F² values for CeAuCd with 14 parameters for each refinement. Geometrical motifs in CeAuCd are two types of gold centered tricapped trigonal prisms: [Au1Cd₃Ce₆] and [Au2Cd₆Ce₃]. The gold and cadmium atoms form a three‐dimensional [AuCd] polyanion in which the cerium atoms fill distorted hexagonal channels. EuAuCd and YbAuCd crystallize with a TiNiSi type structure, space group Pnma: a = 755.2(1), b = 450.59(5), c = 878.6(1) pm, wR2 = 0.0904, 500 F² values for EuAuCd, and a = 731.64(3), b = 432.94(2), c = 875.80(4) pm, wR2 = 0.1192, 457 F² values for YbAuCd with 20 parameters for each refinement. In these structures the europium(ytterbium) and cadmium atoms form zig‐zag chains of egde‐ and face‐sharing trigonal prisms which are centered by the gold atoms. Also in EuAuCd and YbAuCd a three‐dimensional [AuCd] polyanion occurs in which the europium(ytterbium) atoms are embedded. Europium and ytterbium are divalent in EuAuCd and YbAuCd. Susceptibility measurements show Pauli paramagnetism for YbAuCd and Curie‐Weiss behavior above 100 K for EuAuCd with an experimental magnetic moment of 7.86(6) μ_B/Eu. Ferromagnetic ordering is detected at 28 K. The saturation magnetic moment is 7.1(1) μ_B/Eu at 1.9 K. ¹⁵¹Eu Mössbauer spectra show an isomer shift of –9.2(2) mm/s and full magnetic hyperfine field splitting at 4.2 K with an internal hyperfine field of 19.5(4) T at the europium nuclei. The RE₂Au₂Cd compounds crystallize with the Mo₂FeB₂ structure, a ternary ordered version of the U₃Si₂ type. These structures may be considered as an intergrowth of distorted CsCl and AlB₂ related slabs of compositions RECd and REAu₂. Chemical bonding in REAuCd and RE₂Au₂Cd is briefly discussed.     

Au/CeO2催化剂的制备及其对CO催化氧化性能的研究

采用水溶液沉淀法和沉积-沉淀法分别制备了CeO2载体及相应Au/CeO2催化剂,以CO氧化反应为表征反应,考察了载体制备条件,催化剂的焙烧温度、预处理温度和气氛以及活性组分负载量对催化剂性能的影响,并对催化剂进行了BET、XRD和TEM表征,分析了影响催化剂活性的原因.结果表明,载体的制备条件对催化剂的活性有一定影响,经微波处理的载体负载活性组分后,由于活性组分和载体的接触较紧密,因此有利于催化剂活性的提高.催化剂的最佳焙烧温度为300℃,最佳活化温度为300℃,气氛为空气,最佳金负载量为4%.     

海胆针状金纳米颗粒用于电催化二氧化碳还原

采用不加表面活性剂的种子介导生长策略合成了具有针状结构的金纳米颗粒, 其针尖处的尖端电场效应能有效富集电解质阳离子并提高二氧化碳局部浓度, 从而提高催化剂的电流密度和一氧化碳选择性, 在 -0.6 V(vs. RHE)时的法拉第效率可以达到96%. 电化学性能测试结果表明, 其高选择性不仅来源于丰富的表面缺陷, 更主要源于其独特的针状结构所带来的尖端电场效应.     

CuII@PAA/PVC mesoporous fibers: A hybrid wedding as a high-performance versatile heterogeneous catalyst for A3, KA2, and decarboxylative A3 reactions

Efforts made on the development of a novel, simple, cost-effective, and efficient approach to fabricate a copper catalyst immobilized on mesoporous poly (acrylic acid)/poly (vinyl chloride) hybrid fibers (Cu^II@PAA/PVC) for versatile catalytic applications in A₃, KA₂, and decarboxylative A₃ couplings has been described in this present work. The characterization of the mesoporous hybrid fibers was well performed by BET, FTIR, SEM, EDX, XPS, and TGA techniques. The pore structure and surface area were calculated by using BET measurement analysis. The obtained mesoporous Cu^II@PAA/PVC fibers exert high catalytic performance in the synthesis of propargylamines via one-pot A₃, KA₂, and decarboxylative A₃ reactions over a series of substrates without employing expensive ligands or inert atmosphere. The active Cu²⁺ species chelating with carboxylate groups in PAA/PVC hybrid fibers plays a key role in the catalysis. Meanwhile, the unique mesoporous structure and fiber morphology facilitate a better mass transfer and enlarge its contact area with substrates in the course of a reaction. Moreover, the Cu²⁺–carboxylate chelation could suppress the leaching of active Cu²⁺ species from the catalyst and thus lead to the catalyst has excellent performance and good durability as well as reusability.     

2—皮考胺树脂的合成及对金和铂族离子的吸附性

前文已报道了一些含杂环功能基树脂对贵金属离子的吸附性。本文按下列反应式合成了大孔型2-皮考胺树脂(2-picolyl amine resin):     

ClONO2与H的反应机理

在密度泛函理论B3LYP/6-31G^*基组下,研究ClONO₂+H→HONO₂+Cl和ClONO₂+H→OH+ClONO(cis)及ClONO₂+H→OH+ClONO(trans)的反应机理.计算得到各可能反应途径的过渡态,并经过内禀反应坐标(IRC)分析加以证实.三个反应的活化能垒(分别为19.5,20.0和23.2kJ·mol^-1)相差不大,可认为同时发生.但第一个反应放出的热量较多,可以看成是反应的主通道.     

F+CH2CO的反应机理和动力学研究

用G3(MP2)方法对F与CH₂CO的反应进行研究,揭示了该反应的加成-消除机理.F原子首先与CH₂CO作用形成富能的中间体CH₂FCO^*,此加成反应为无势垒过程.富能的CH₂FCO^*可进一步发生解离或异构化反应生成各种可能的产物.其中CO和CH₂F可能为反应的主要产物.根据从头算的结果,用RRKM-TST理论计算该反应的速率常数.总包反应速率常数与温度存在弱的依赖关系,与总压力无关.     

Small Size Effect and Concentration Response of Gold Nanoparticles in Electrochemiluminescence Reaction

Recent reports have used gold nanoparticles (AuNPs) as a co‐reactant for the electrochemiluminescence (ECL) reaction of ruthenium complex. However, understanding the size effect of AuNPs on ECL reaction is very meaningful to explore its unknowns and develop its applications at the molecular level. In this paper, we examined the behavior of various small‐size AuNPs in ECL reaction, focusing on changes in ECL caused by AuNPs size and reasons for this change. Although the luminescence spectra and excitation potential have hardly changed in ECL reaction, the difference of ECL intensities induced by different sizes AuNPs is very obviously. Our experimental results revealed disparate behaviors depending on AuNPs size: the small‐sized AuNPs can lead to stronger ECL, and ECL intensities increase as the addition of AuNPs concentration in the wider range. This small size effect is related to an intermediate process of charge‐discharge in electric double layer formed by adsorbing ruthenium complex with AuNPs, and the surface and quantum size effect of AuNPs may affect this intermediate process. More importantly, AuNPs can act as a marker, has the same small size effect and concentration response, and bring about a promising platform for biochemical analysis.     

Effect of Cesium Modification on CuO/CeO2 Catalysts for the Catalytic Decomposition of N2O

A series of Cs-modified CuO/CeO2 mixed oxide catalysts was prepared for enhancing the stable activity of N2O decomposition.It was found that Cs modification promoted the catalytic performance of CuO/CeO2 catalysts significantly,The l%Cs-CuO/CeO2 catalyst exhibited the best activity,and the conversion of N2O reached 100%at 380℃ in the presence of 2% O2.The catalytic behaviors were investigated by means of XRD,N2 adsorption isotherms,XPS,H2-TPR(TPR:temperature-prograrmmed reduction),CO-IR,O2-TPD(TPD:temperature-programmed desorption)and diffused reflectance infrared Fourier transform spectorscopy(DRiFTs).The results revealed that Cs modification promoted the activity and the oxygen resistance by enhancing the desorption of surface oxygen species and increasing the content of Ce^3+.CO-DRIFTs revealed that Ce^3+could efficiently facilitate the regeneration of active Cu^+sites by an oxygen migration step.The possible reaction mechanism was also discussed.     

高导电性和催化活性的Janus-TiNbCO2析氢反应催化材料

探寻具有高导电性和高催化活性的析氢反应（HER）催化材料一直是可持续能源发展研究中的热点。Ti₂C具有表面活性位点多和优良的力学稳定性、导电性等,已成为潜在的制氢催化剂。然而,终端O修饰Ti₂C表面,会降低该材料的导电性,进而限制了电子在价带与导带间的输运。本研究通过Nb掺杂,构建双电层Janus-TiNbCO₂,并借助VASP软件研究了Janus-TiNbCO₂的能带结构、HER性能和HER反应路径过渡态。结果表明,Janus-TiNb-CO₂为导体材料,其在应力、氧空位缺陷和H*覆盖度的影响下,均表现出极优异的催化活性,计算获得的最优ΔG_H*值为0.02 eV。H*在Janus-TiNbCO₂上可能以Heyrovsky路径进行反应,该路径的迁移能势垒为0.23 eV。Janus-TiNbCO₂是一种具有HER应用前景的催化材料。     

Gold(I)-Catalyzed Bis-Cyclization of Allenynes for the Synthesis of Strained and Planar Polycyclic Compounds

A gold-catalyzed cascade cyclization of naphthalene-tethered allenynes gave strained fused phenanthrene derivatives. The reaction proceeds through the nucleophilic reaction of an alkyne with the activated allene to generate a vinyl cation intermediate, followed by arylation with a tethered naphthalene ring to form the 4H-cyclopenta[def]phenanthrene (CPP) scaffold. When using aryl-substituted substrates on the alkyne terminus, the gold-catalyzed reaction produced dibenzofluorene derivatives along with the CPP derivatives. Selective formation of CPP and dibenzofluorene derivatives depending on the reaction conditions is also presented.