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1.
Yingying Liu Dr. Siu‐Mui Ng Dr. Shek‐Man Yiu Dr. William W. Y. Lam Xi‐Guang Wei Dr. Kai‐Chung Lau Prof. Tai‐Chu Lau 《Angewandte Chemie (International ed. in English)》2014,53(52):14468-14471
Polypyridyl and related ligands have been widely used for the development of water oxidation catalysts. Supposedly these ligands are oxidation‐resistant and can stabilize high‐oxidation‐state intermediates. In this work a series of ruthenium(II) complexes [Ru(qpy)(L)2]2+ (qpy=2,2′:6′,2′′:6′′,2′′′‐quaterpyridine; L=substituted pyridine) have been synthesized and found to catalyze CeIV‐driven water oxidation, with turnover numbers of up to 2100. However, these ruthenium complexes are found to function only as precatalysts; first, they have to be oxidized to the qpy‐N,N′′′‐dioxide (ONNO) complexes [Ru(ONNO)(L)2]3+ which are the real catalysts for water oxidation. 相似文献
2.
Ming-Tsz Chen Yu-Yang Chen Guan-Lin Li Kai-Wen Chou Ching-Han Hu Guo-Cyuan Huang Chi-Tien Chen 《应用有机金属化学》2020,34(4):e5464
This paper describes the effect of solvent-induced synthetic routes of aluminium pendant oxazoline-amido-phenolate complexes. Treatment of ligand precursor L with AlMe3 in a 1:1 ratio in diethyl ether yielded the four-coordinated complex (LAlMe)2. Reaction of ligand precursor L with AlMe3 in a 1:2 ratio in hexane generated the four-coordinated complex L(AlMe2)2. A novel transformation mode occurred from L(AlMe2)2 to (LAlMe)2 when using diethyl ether or tetrahydrofuran as solvent. A density functional theory computational study also supports a plausible mechanism. All results were supported by spectroscopic data and in agreement with single-crystal X-ray diffraction structural analysis. 相似文献
3.
Dr. Simon Petrie Dr. Richard Terrett Prof. Robert Stranger Prof. Ron J. Pace 《Chemphyschem》2020,21(8):785-801
Three atomic resolution crystal structures of Photosystem II, in the double flashed, nominal S3 intermediate state of its Mn4Ca Water Oxidising Complex (WOC), have now been presented, at 2.25, 2.35 and 2.08 Å resolution. Although very similar overall, the S3 structures differ within the WOC catalytic site. The 2.25 Å structure contains only one oxy species (O5) in the WOC cavity, weakly associated with Mn centres, similar to that in the earlier 1.95 Å S1 structure. The 2.35 Å structure shows two such species (O5, O6), with the Mn centres and O5 positioned as in the 2.25 Å structure and O5−O6 separation of ∼1.5 Å. In the latest S3 variant, two oxy species are also seen (O5, Ox), with the Ox group appearing only in S3, closely ligating one Mn, with O5−Ox separation <2.1 Å. The O5 and O6/Ox groups were proposed to be substrate water derived species. Recently, Petrie et al. (Chem. Phys. Chem., 2017 ) presented large scale Quantum Chemical modelling of the 2.25 Å structure, quantitatively explaining all significant features within the WOC region. This, as in our earlier studies, assumed a ‘low’ Mn oxidation paradigm (mean S1 Mn oxidation level of +3.0, Petrie et al., Angew. Chem. Int. Ed., 2015 ), rather than a ‘high’ oxidation model (mean S1 oxidation level of +3.5). In 2018 we showed (Chem. Phys. Chem., 2018 ) this oxidation state assumption predicted two energetically close S3 structural forms, one with the metal centres and O5 (as OH−) positioned as in the 2.25 Å structure, and the other with the metals similarly placed, but with O5 (as H2O) located in the O6 position of the 2.35 Å structure. The 2.35 Å two flashed structure was likely a crystal superposition of two such forms. Here we show, by similar computational analysis, that the latest 2.08 Å S3 structure is also a likely superposition of forms, but with O5 (as OH−) occupying either the O5 or Ox positions in the WOC cavity. This highlights a remarkable structural ‘lability’ of the WOC centre in the S3 state, which is likely catalytically relevant to its water splitting function. 相似文献
4.
The theoretical knowledge about the zinc-zinc bond has been recently expanded after the proposal of a zinc-zinc double bond in several [Zn2(L)4] compounds (Angew. Chem. Int. Ed. 2017 , 56, 10151-10155). Prompted by these results, we have selected the [Zn2(CO)4] species, isolobally related to ethylene, and theoretically investigated the possible η2-Zn2-coordination to several first-row transition metal fragments. The [Zn2(CO)4] coordination to the metal fragment produces an elongation of the dizinc bond and a concomitant pyramidalization of the [Zn(CO)2] unit. These structural parameters are indicative of π-backdonation from the metal to the coordinated dizinc moiety, as occurred with ethylene ligand. A quantum theory of atoms in molecules study of the Zn Zn bond shows a decrease of ρBCP, ∇2ρBCP ∫Zn∩Znρ and delocalization indexes δ(Zn,Zn), relative to corresponding values in the parent [Zn2(CO)4] molecule. The Zn Zn and M Zn bonds in these [(η2-Zn2(CO)4)M(L)n] complexes can be described as shared interactions with an important covalent component where the Zn Zn bond is preserved, albeit weakened, upon coordination. 相似文献
5.
6.
Ying-Ying Li Dr. Carolina Gimbert Prof. Dr. Antoni Llobet Prof. Dr. Per E. M. Siegbahn Prof. Dr. Rong-Zhen Liao 《ChemSusChem》2019,12(5):1101-1110
The heterotrinuclear complex A {[RuII(H2O)(tpy)]2(μ-[MnII(H2O)2(bpp)2])}4+ [tpy=2,2′:6′,2′′-terpyridine, bpp=3,5-bis(2-pyridyl)pyrazolate] was found to catalyze water oxidation both electrochemically and photochemically with [Ru(bpy)3]3+ (bpy=2,2′-bipyridine) as the photosensitizer and Na2S2O8 as the electron acceptor in neutral phosphate buffer. The mechanism of water oxidation catalyzed by this unprecedented trinuclear complex was studied by density functional calculations. The calculations showed that a series of oxidation and deprotonation events take place from A , leading to the formation of complex 1 (formal oxidation state of Ru1IVMnIIIRu2III), which is the starting species for the catalytic cycle. Three sequential oxidations of 1 result in the generation of the catalytically competing species 4 (formal oxidation state of Ru1IVMnVRu2IV), which triggers the O−O bond formation. The direct coupling of two adjacent oxo ligands bound to Ru and Mn leads to the production of a superoxide intermediate Int1 . This step was calculated to have a barrier of 7.2 kcal mol−1 at the B3LYP*-D3 level. Subsequent O2 release from Int1 turns out to be quite facile. Other possible pathways were found to be much less favorable, including water nucleophilic attack, the coupling of an oxo and a hydroxide, and the direct coupling pathway at a lower oxidation state (RuIVMnIVRuIV). 相似文献
7.
A series of neutral binuclear iridium and rhodium complexes were synthesized based on bis‐imine ligands under mild conditions. These half‐sandwich late transition metal complexes were isolated in good yields and characterized by elemental analysis, 1H NMR, 13C NMR, HR‐MS, and FT‐IR spectroscopies, and the solid state structure of complexes 1 and 2 were further confirmed by single‐crystal X‐ray diffraction. Cyclic voltammetry (CV) characterization indicated that the complex 1 has the best catalyst for water oxidation process with TOF of 0.8 s?1 at low overpotential of 0.325 V in methanol‐phosphate buffer. The proposed double‐site water oxidation mechanism had been also speculated . 相似文献
8.
Li Ma Qian Wang Dr. Wai‐Lun Man Dr. Hoi‐Ki Kwong Dr. Chi‐Chiu Ko Prof. Tai‐Chu Lau 《Angewandte Chemie (International ed. in English)》2015,54(17):5246-5249
The study of manganese complexes as water‐oxidation catalysts (WOCs) is of great interest because they can serve as models for the oxygen‐evolving complex of photosystem II. In most of the reported Mn‐based WOCs, manganese exists in the oxidation states III or IV, and the catalysts generally give low turnovers, especially with one‐electron oxidants such as CeIV. Now, a different class of Mn‐based catalysts, namely manganese(V)–nitrido complexes, were explored. The complex [MnV(N)(CN)4]2− turned out to be an active homogeneous WOC using (NH4)2[Ce(NO3)6] as the terminal oxidant, with a turnover number of higher than 180 and a maximum turnover frequency of 6 min−1. The study suggests that active WOCs may be constructed based on the MnV(N) platform. 相似文献
9.
Density functional theory calculations were utilized to elucidate the water oxidation mechanism catalyzed by polyanionic tetramanganese complex a [MnIII3MnIVO3(CH3COO)3(A-α-SiW9O34)]6−. Theoretical results indicated that catalytic active species 1 (Mn4III,III,IV,IV) was formed after O2 formation in the first turnover. From 1 , three sequential proton-coupled electron transfer (PCET) oxidations led to the MnIV-oxyl radical 4 (Mn4IV,IV,IV,IV−O⋅). Importantly, 4 had an unusual butterfly-shaped Mn2O2 core for the two substrate-coordinated Mn sites, which facilitated O−O bond formation via direct coupling of the oxyl radical and the adjacent MnIV-coordinated hydroxide to produce the hydroperoxide intermediate Int1 (Mn4III,IV,IV,IV−OOH). This step had an overall energy barrier of 24.9 kcal mol−1. Subsequent PCET oxidation of Int1 to Int2 (Mn4III,IV,IV,IV−O2⋅) enabled the O2 release in a facile process. Furthermore, apart from the Si-centered complex, computational study suggested that tetramanganese polyoxometalates with Ge, P, and S could also catalyze the water oxidation process, where those bearing P and S likely present higher activities. 相似文献
10.
《International journal of quantum chemistry》2018,118(15)
Focusing on the competing pathways of methanol oxidation on platinum and platinum/gold bimetallic catalysts, we explore a novel density functional theory (DFT)‐based approach to the study of reactions on catalyst surfaces. Traditionally, DFT has been used to compute binding energies of products and intermediates as proxies for catalytic activity, and to compute full reaction pathways and their activation energy barriers. Merging the computational simplicity and intuitive clarity of binding energy calculations with the site sensitivity of transition state calculations, we construct maps of the binding energies of relevant atoms and molecules at all sites on a surface. We show that knowledge of the arrangement of strong and weak binding sites on a surface is powerful in rationalizing the ease with which a reaction step proceeds on a given local motif of surface atoms. We highlight the prospects and challenges of this approach toward catalyst screening and prediction. 相似文献
11.
Vanessa A. dos Santos Lidia S. Shul''pina Dario Veghini Dalmo Mandelli Georgiy B. Shul''pin 《Reaction Kinetics and Catalysis Letters》2006,88(2):339-348
Summary The dinuclear manganese(IV) complex [LMn(O)3MnL](PF6)2 (1, L = 1,4,7-trimethyl-1,4,7-triazacyclononane) catalyzes the extremely efficient oxidation of alcohols with hydrogen peroxide
at room temperature. Oxalic acid is an obligatory co-catalyst. The oxidation of isopropanol, for example, yields acetone with
turnover numbers up to 40000 after 5-10 h in the absence of a solvent. 2-Cyanoethanol was oxidized by this system with somewhat
lower efficiency (conversion 70%). The catalytically active cation from salt 1 was obtained in an insoluble form containing
a heteropoly anion [Mn2O3(TMTACN)2]2[SiW12O40]. Oxidation of 2-cyanoethanol using this heterogenized catalyst and oxalic acid gave the oxo-products with the 54% total
yield. 相似文献
12.
Dr. Xichen Li Prof. Per E. M. Siegbahn 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(51):18821-18827
For the main parts of the mechanism for water oxidation in photosystem II there has recently been very strong experimental support for the mechanism suggested by theoretical model studies. The question addressed in the present study is to what extent this knowledge can be used for the design of artificial catalysts. A major requirement for a useful artificial catalyst is that it is small enough to be synthesized. Small catalysts also have the big advantage that they could improve the catalysis per surface area. To make the mechanism found for PSII useful in this context, it needs to be analyzed in detail. A small model system was therefore used and the ligands were replaced one by one by water‐derived ligands. Only the main chemical step of O?O bond formation was investigated in this initial study. The energetics for this small model and the larger one previously used for PSII are remarkably similar, which is the most important result of the present study. This shows that small model complexes have a potential for being very good water oxidation catalysts. It was furthermore found that there is a clear correlation between the barrier height for O?O bond formation and the type of optimal structure for the S3 state. The analysis shows that a flexible central part of the complex is the key for efficient water oxidation. 相似文献
13.
We have studied the CO oxidation over neutral, anionic, and cationic gold hexamer clusters using density functional theory which elucidates the effect of cluster charge state on the catalytic activity. Herein, we have considered the conventional bimolecular Langmuir–Hinshelwood mechanism with coadsorbed CO and O2 at the neighboring sites in all the clusters. Among the three clusters, entails lower barriers during the various steps of the oxidation mechanism. The stability of all the species including the transition states with respect to the interacting species in indicates no thermal activation. Our study suggests better catalytic activity of as compared to the neutral and cationic counterparts. © 2014 Wiley Periodicals, Inc. 相似文献
14.
15.
Yongzhao Su Zhicheng Chen Dr. Jiangnan Huang Dr. Hongjuan Wang Prof. Hao Yu Dr. Qiao Zhang Dr. Yonghai Cao Prof. Feng Peng 《ChemCatChem》2022,14(2):e202101378
Aerobic oxidation of hydrocarbons yielding corresponding oxygenated products is one of the most important chemical processes. In current work, carbon nanotubes supported encapsulated cobalt nanoparticles with carbon layers (Co@C/CNTs) were synthesized and utilized as catalysts in the oxidation of ethylbenzene (EB) in the liquid phase, exhibiting high catalytic performance. The synergistic effect between Co@C and CNTs played the vital role on facilitating the decomposition of peroxides to enhance the overall activity. The inadequate covered Co@C on CNTs surface were considered as catalytic sites. Density functional theory revealed that the exist of Co nanoparticles could improve the interaction between the catalyst and intermediate free radicals, which were significant for EB oxidation. Last but not least, the electron transfer on carbon surface was enhanced by the incorporation of Co@C nanoparticles, which greatly improved the catalytic performance on EB oxidation. This study provides a new insight into the Co-based catalysts in the aerobic oxidation of hydrocarbons. 相似文献
16.
Khusnutdinov R. I. Schadneva N. A. Baiguzina A. R. Dzhemilev U. M. 《Russian Chemical Bulletin》2002,51(6):1065-1067
The Mn(acac)3—RCN—CCl4 system was found to be efficient for the oxidation of secondary alcohols into the corresponding ketones in 80—93% yields. The oxidation proceeds through the formation of alkyl hypochlorites, which are generated from CCl4 and the alcohols in the presence of the Mn(acac)3—RCN catalytic system (R = Me, Et, and Ph). 相似文献
17.
Wang HF Kavanagh R Guo YL Guo Y Lu GZ Hu P 《Angewandte Chemie (International ed. in English)》2012,51(27):6657-6661
18.
实验发现纳米金催化的CO氧化有良好的湿度增强效应,但有关机制仍不清楚.我们应用密度泛函理论研究了湿度增强效应的微观机制,以Au4团簇为例,研究了金催化CO氧化的微观机理,考察了H2O在反应中的角色和作用.计算结果表明,H2O与Au4团簇一样,在反应中扮演催化剂的角色,参与反应的进行、改变反应历程、降低反应能垒.催化循环包含4个基元步骤：O2＋H2O→OOH＋OH,CO＋OOH→CO2＋OH,CO＋OH→COOH,和COOH＋OH→CO2＋H2O,其中自由基OOH和OH的形成是催化循环的速控步骤,其能垒为100.31kJ/mol,明显低于非水参与反应的能垒（161.41kJ/mol）.目前的结果合理地解释了实验观测的CO催化氧化的湿度增强效应,给出了其微观反应机制. 相似文献
19.
采用密度泛函理论研究气相和四氢呋喃（THF）溶剂中Cp4An和COT2An（Cp-=C5H5-,COT2-=C8H82-,An=U（IV）,Pu（IV））配合物的性质。THF溶剂对配合物的溶剂化效应采用类导体极化连续模型（CPCM）近似计算。计算结果显示在THF溶液中各配合物结合能的大小顺序为COT2Pu > COT2U > Cp4Pu > Cp4U。溶剂化效应降低了该金属有机配合物的结合能。计算得到的化合物的结构参数和红外光谱数据与实验数据保持一致。通过对Cp4An和COT2An（An=U（IV）,Pu（IV））的分子轨道能级图分析发现,采用最高的RSC ECP赝势计算COT2U和Cp4U的基态分别为三重fφ2和fσ2组态;而COT2Pu和Cp4Pu的基态分别为五重fσ1fπ1fφ1和fσ3fδ1组态。 相似文献
20.
采用密度泛函理论研究气相和四氢呋喃（THF）溶剂中Cp4An和COT2An（Cp-=C5H5-,COT2-=C8H2-,An=U(Ⅳ),Pu(Ⅳ)）配合物的性质。THF溶剂对配合物的溶剂化效应采用类导体极化连续模型（CPCM）近似计算。计算结果显示在THF溶液中各配合物结合能的大小顺序为COT2Pu > COT2U > Cp4Pu > Cp4U。溶剂化效应降低了该金属有机配合物的结合能。计算得到的化合物的结构参数和红外光谱数据与实验数据保持一致。通过对Cp4An和COT2An（An=U(Ⅳ),Pu(Ⅳ)）的分子轨道能级图分析发现,采用最高的RSC-ECP赝势计算COT2U和Cp4U的基态分别为三重fφ2和fσ2组态;而COT2Pu和Cp4Pu的基态分别为五重fσ1fπ1fφ2和fσ3fδ1组态。 相似文献