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Díaz, Urbano, Mercedes Boronat i Avelino Corma. "Hybrid organic–inorganic structured materials as single-site heterogeneous catalysts". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 468, nr 2143 (14.03.2012): 1927–54. http://dx.doi.org/10.1098/rspa.2012.0066.
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Catalyst selectivity is associated with well-defined homogeneous active sites. Transition metal complexes and organocatalysts are highly active and selective in the homogeneous phase, and their heterogenization by incorporating them into inorganic solid materials allows combining their excellent catalytic activity with improved separation, recovering and recycling properties. In this article, we present the structural characteristics and catalytic properties of hybrid organic–inorganic materials in which the molecular catalysts are part of the inorganic structure, emphasizing the possibilities of periodic mesoporous hybrid materials and coordination polymers as single-site solid catalysts.
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Shen, Siqi, Yuanyuan Sun, Hao Sun, Yuepeng Pang, Shuixin Xia, Taiqiang Chen, Shiyou Zheng i Tao Yuan. "Research Progress in ZIF-8 Derived Single Atomic Catalysts for Oxygen Reduction Reaction". Catalysts 12, nr 5 (7.05.2022): 525. http://dx.doi.org/10.3390/catal12050525.
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Transition metal (TM) single atomic catalysts (MSAC-N-C) derived from doped zeolite imidazolate frameworks (ZIF-8) are considered attractive oxygen reduction reaction (ORR) catalysts for fuel cells and metal-air batteries due to their advantages of high specific surface area, more active catalytic sites, adjustable pore size, and coordination topology features. This review provides an updated overview of the latest advances of MSAC-N-C catalysts derived from ZIF-8 precursors in ORR electrocatalysis. Particularly, some key challenges, including coordination environments regulation of catalysis center in MSAC-N-C, the active sites loading optimization and synergistic effects between TM nanoclusters/nanoparticles and the single atoms on MSAC-N-C catalysis activity, as well as their adaptability in various devices, are summarized for improving future development and application of MSAC-N-C catalysts. In addition, this review puts forward future research directions, making it play a better role in ORR catalysis for fuel cells and metal air batteries.
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Li, Zhen, Zhen Wang, Nikita Chekshin, Shaoqun Qian, Jennifer X. Qiao, Peter T. Cheng, Kap-Sun Yeung, William R. Ewing i Jin-Quan Yu. "A tautomeric ligand enables directed C‒H hydroxylation with molecular oxygen". Science 372, nr 6549 (24.06.2021): 1452–57. http://dx.doi.org/10.1126/science.abg2362.
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Hydroxylation of aryl carbon–hydrogen bonds with transition metal catalysts has proven challenging when oxygen is used as the oxidant. Here, we report a palladium complex bearing a bidentate pyridine/pyridone ligand that efficiently catalyzes this reaction at ring positions adjacent to carboxylic acids. Infrared, x-ray, and computational analysis support a possible role of ligand tautomerization from mono-anionic (L,X) to neutral (L,L) coordination in the catalytic cycle of aerobic carbon–hydrogen hydroxylation reaction. The conventional site selectivity dictated by heterocycles is overturned by this catalyst, thus allowing late-stage modification of compounds of pharmaceutical interest at previously inaccessible sites.
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Gao, Guoping, Steven Bottle i Aijun Du. "Understanding the activity and selectivity of single atom catalysts for hydrogen and oxygen evolution via ab initial study". Catalysis Science & Technology 8, nr 4 (2018): 996–1001. http://dx.doi.org/10.1039/c7cy02463k.
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To identify the specific activity sites for both the HER and OER in experimental realized single transition-metal atom decorated graphene sheets, we assume the number of metal–C bonds (coordination) determines the adsorption strength of reaction intermediates on the metal atom sites.
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Al-Riyahee, Ali A. A. "First Row Transition Metal Complexes Derived from N, Nʹ-Substituted Thiourea: Synthesis, Geometrical Structures and Cyclic Voltammetry Probe: A Review". BASRA JOURNAL OF SCIENCE 39, nr 1 (1.01.2021): 96–118. http://dx.doi.org/10.29072/basjs.202117.
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Thioureas or thiourea derivatives as organosulfur compounds are one of the most widely used ligands in different applications as we are going to discuss it extensively such as in coordination chemistry by involving them to rich sources of N, O and S atoms coordinating through S atom, S and O atoms in benzoyl derivatives or S, O and N atoms in pyridyl hetrocylic benzoyl derivatives. These hard and soft donor sites facilitate the bonding between thiourea free ligand and metal ion through one or more to make ligands behave as mono, bi or multidentate ligands to form huge and stable series of the metal complexes. The tautomerism (thiol↔thione) inside the thiourea derivatives is responsible on their flexibility which make them easy capable to coordinate in different modes. Thiourea derivatives and their metal complexes are known in biological area by possess them antibacterial, antifungal, antimalarial, antitubercular, antithyroid and insecticidal activity features. Thioureas used as vital reagent to separate metal ions, catalyst to synthesize organic compounds or as starting material to form different hetrocyclic compounds. The wide range applications of thioureas and their metal complexes has motivated specialized researchers to search new applications for these compounds and to create a novel derivatives. The goal of this article is to present historical survey of thioureas and their metal complexes focusing on: firstly, the development of their synthetic routes by explore reactants, products, catalysis and the conditions of reactions. Secondly: investigation of the geometrical shapes of the produced complexes are reviewed as well as to the coordinated sites with metal centers. Lastly, the electrochemical manners have been lighted by employing cyclic voltammetry (CV) to study the electrochemical behavior of free ligands and their complexes to confirm the oxidation state of the metal ion in its complexes.
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Rao, C. N. R., P. Vishnu Kamath, K. Prabhakaran i M. S. Hegde. "Adsorption of carbon monoxide on the surfaces of polycrystalline transition metals and alloys: electron energy loss and ultraviolet photoelectron spectral studies". Canadian Journal of Chemistry 63, nr 7 (1.07.1985): 1780–87. http://dx.doi.org/10.1139/v85-298.
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Adsorption of CO has been investigated on the surfaces of polycrystalline transition metals as well as alloys by employing electron energy loss spectroscopy (eels) and ultraviolet photoelectron spectroscopy (ups). CO adsorbs on polycrystalline transition metal surfaces with a multiplicity of sites, each being associated with a characteristic CO stretching frequency; the relative intensities vary with temperature as well as coverage. Whilst at low temperatures (80–120 K), low coordination sites are stabilized, the higher coordination sites are stabilized at higher temperatures (270–300 K). Adsorption on surfaces of polycrystalline alloys gives characteristic stretching frequencies due to the constituent metal sites. Alloying, however, causes a shift in the stretching frequencies, indicating the effect of the band structure on the nature of adsorption. The up spectra provide confirmatory evidence for the existence of separate metal sites in the alloys as well as for the high-temperature and low-temperature phases of adsorbed CO.
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Zeng, Xianshi, Chuncai Xiao, Luliang Liao, Zongxing Tu, Zhangli Lai, Kai Xiong i Yufeng Wen. "Two-Dimensional (2D) TM-Tetrahydroxyquinone Metal–Organic Framework for Selective CO2 Electrocatalysis: A DFT Investigation". Nanomaterials 12, nr 22 (17.11.2022): 4049. http://dx.doi.org/10.3390/nano12224049.
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The resource utilization of CO2 is one of the essential avenues to realize the goal of “double carbon”. The metal–organic framework (MOF) has shown promising applications in CO2 catalytic reduction reactions due to its sufficient pore structure, abundant active sites and functionalizability. In this paper, we investigated the electrocatalytic carbon dioxide reduction reactions of single-atom catalysts created by MOF two-dimensional coordination network materials constructed from transition metal-tetrahydroxybenzoquinone using density function theory calculations. The results indicate that for 10 transition metals, TM-THQ single levels ranging from Sc to Zn, the metal atom binding energy to the THQ is large enough to allow the metal atoms to be stably dispersed in the THQ monolayer. The Ni-THQ catalyst does not compete with the HER reaction in an electrocatalytic CO2 reduction. The primary product of reduction for Sc-THQ is HCOOH, but the major product of Co-THQ is HCHO. The main product of Cu-THQ is CO, while the main product of six catalysts, Ti, V, Cr, Mn, Fe, and Zn, is CH4. The limit potential and overpotential of Ti-THQ are the highest, 1.043 V and 1.212 V, respectively. The overpotentials of the other monolayer catalysts ranged from 0.172 to 0.952 V, and they were all relatively low. Therefore, we forecast that the TM-HQ monolayer will show powerful activity in electrocatalytic carbon dioxide reduction, making it a prospective electrocatalyst for carbon dioxide reduction.
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Kopchuk, Dmitry S., Grigory A. Kim, Igor S. Kovalev, Sougata Santra, Grigory V. Zyryanov, Adinath Majee, Vladimir L. Rusinov i Oleg N. Chupakhin. "Tripod-type 2,2′-bipyridine ligand for lanthanide cations: synthesis and photophysical studies on coordination to transition metal cations". Canadian Journal of Chemistry 96, nr 4 (kwiecień 2018): 419–24. http://dx.doi.org/10.1139/cjc-2017-0485.
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New tripod-type 2,2′-bipyridine ligand consisting of a central polyaminocarboxylic moiety for the coordination to lanthanide cations and three appended 5-phenyl-2,2′-bipyridine fragments for the coordination to various transition metal cations have been prepared. A europium complex of this ligand was prepared, and its photophysical properties and a luminescent response towards transition metal salts (particularly, CdI2, Cd(OAc)2, Zn(ClO4)2, Cu(OAc)2, and HgCl2) have been studied. Europium cation luminescence quenching in the presence of transition metal salts in solution was observed in all cases. In addition, it was observed that the fluorescent response of the europium complex was quite individual depending on the type of the metal salt. The obtained data were compared with the earlier published data for some lanthanide complexes bearing additional sites for the chelation of transition metal cations.
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Hsieh, Meng-Chi, Ranganathan Krishnan i Ming-Kang Tsai. "Formic Acid Generation from CO2 Reduction by MOF-253 Coordinated Transition Metal Complexes: A Computational Chemistry Perspective". Catalysts 12, nr 8 (12.08.2022): 890. http://dx.doi.org/10.3390/catal12080890.
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The inclusion of transition metal elements within metal–organic frameworks (MOFs) is considered one of the most promising approaches for enhancing the catalytic capability of MOFs. In this study, MOF-253 containing bipyridine coordination sites is investigated for possible transition metal chelation, and a consequent possible CO2 reduction mechanism in the formation of formic acid. All transition metal elements of the third, fourth and fifth periods except hafnium and the lanthanide series are considered using density functional theory calculations. Two distinct types of CO2 reduction mechanisms are identified: (1) the five-coordination Pd center, which promotes formic acid generation via an intramolecular proton transfer pathway; (2) several four-coordination metal centers, including Mn, Pd, and Pt, which generate formic acid by means of heterolytic hydrogen activation. The MOF-253 environment is found to promote beneficial steric hindrance, and to constrain metal–ligand orientation, which consequently facilitates the formation of formic acid, particularly with the tetrahedral Mn center at high-spin electronic state.
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Nizameev, Irek R., Danis M. Kadirov, Guliya R. Nizameeva, Aigul’ F. Sabirova, Kirill V. Kholin, Mikhail V. Morozov, Lyubov’ G. Mironova i in. "Complexes of Sodium Pectate with Nickel for Hydrogen Oxidation and Oxygen Reduction in Proton-Exchange Membrane Fuel Cells". International Journal of Molecular Sciences 23, nr 22 (17.11.2022): 14247. http://dx.doi.org/10.3390/ijms232214247.
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A number of nickel complexes of sodium pectate with varied Ni2+ content have been synthesized and characterized. The presence of the proton conductivity, the possibility of the formation of a dense spatial network of transition metals in these coordination biopolymers, and the immobilization of transition ions in the catalytic sites of this class of compounds make them promising for proton-exchange membrane fuel cells. It has been established that the catalytic system composed of a coordination biopolymer with 20% substitution of sodium ions for divalent nickel ions, Ni (20%)-NaPG, is the leading catalyst in the series of 5, 15, 20, 25, 35% substituted pectates. Among the possible reasons for the improvement in performance the larger specific surface area of this sample compared to the other studied materials and the narrowest distribution of the vertical size of metal arrays were registered. The highest activity during CV and proximity to four-electron transfer during the catalytic cycle have also been observed for this compound.
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Patniboon, Tipaporn, i Heine Anton Hansen. "Effects of electrolyte anion adsorption on the activity and stability of single atom electrocatalysts". Chemical Physics Reviews 4, nr 1 (marzec 2023): 011401. http://dx.doi.org/10.1063/5.0125654.
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A single metal site incorporated in N-doped carbon (M/N/C) is a promising electrocatalyst. Here, we perform a computation investigation of the effect of electrolyte anion adsorption on the activity and stability of single-atom catalysts (MN4) with M as transition metal and p-block metal. The MN4 site on two different graphene structures (bulk graphene and graphene edge) is studied under electrochemical conditions for the oxygen reduction reaction (ORR) and the CO2 reduction reaction (CO2RR). Because of the two-dimensional nature of the catalyst, reaction intermediates and electrolyte ions can interact with both sides of the single-atom catalyst. As a result, the electrolyte anions compete with water and adsorbate on the single metal site, in some cases either poisoning or modifying the catalyst activity and thermodynamic stability. We find most electrolyte anions adsorbs on the single metal site under ORR conditions but not at the lower potentials for the CO2RR. Still, the adsorption of water and gas molecules can occur under CO2RR conditions. For example, under ORR conditions, the thermodynamic driving force of the *SO4-FeN4 site in the 0.1 M H2SO4 solution is about 0.47–0.56 eV lower than the *O-FeN4 site in water, depending on the local carbon structure. Additionally, the stabilization by electrolyte anions depends on the nature of the metal atom. Our study demonstrates the important role of electrolytes and the coordination environment for the activity and stability of the M/N/C catalyst.
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Svengren, H., N. Torapava, I. Athanassiadis, S. I. Ali i M. Johnsson. "A transition metal oxofluoride offering advantages in electrocatalysis and potential use in applications". Faraday Discussions 188 (2016): 481–98. http://dx.doi.org/10.1039/c5fd00169b.
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The recently described solid solution (Co,Ni,Mn)3Sb4O6F6has proved stable and efficient as a catalyst for electrocatalytic water oxidation. The end component Co3Sb4O6F6was found to be most efficient, maintaining a current density ofj= 10 mA cm−2at an overpotential of 443 mV with good capability. At this current density, O2and H2were produced in the ratio 1 : 2 without loss of faradaic current against a Pt-cathode. A morphological change in the crystallite surface was observed after 0.5 h, however, even after 64.5 h, the overall shape and size of the small crystallites were unaffected and the electrolyte contained only 0.02 at% Co. It was also possible to conclude fromin situEXAFS measurements that the coordination around Co did not change. The oxofluorides express both hydrophilic and hydrophobic surface sites, incorporate a flexible metalloid element and offer the possibility of a mechanism that differs from other inorganic catalytic pathways previously described.
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Xia, Zhonghong, Rongying Zhu, Renqin Yu, Shiming Zhang, Joey Chung-Yen Jung i Jiujun Zhang. "Review—Recent Progress in Highly Efficient Oxygen Reduction Electrocatalysts: From Structural Engineering to Performance Optimization". Journal of The Electrochemical Society 169, nr 3 (1.03.2022): 034512. http://dx.doi.org/10.1149/1945-7111/ac593b.
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Oxygen reduction reaction (ORR) is one of the most important reactions in practical electrochemical energy devices such as fuel cells and metal-air batteries. In this paper, the recent advancements in platinum-group-metals-based alloys including Pt and/or Pd alloys with the late transitional metals for ORR electrocatalysis are reviewed in terms of catalyst synthesis, characterization, functional mechanism and the validation of performance (activities and stabilities) in both acidic and alkaline electrolytes. The electronic tuning and structural design/engineering for inducing lattice strain, favorable coordination environment, defects, vacancies, etc. for catalytic ORR active sites are emphasized. Morphologically, zero- to three-dimensional ORR catalysts with remarkable performances are introduced. For facilitating further research and development, several challenges are analyzed and the corresponding research directions for overcoming the challenges are also proposed.
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Atanassov, Plamen, Yechuan Chen, Tristan Asset, Yuanchao Liu, Eamonn Murphy i Ivana Matanovic. "(Keynote) Mechanistic Understanding of the Activity of Atomically Dispersed Transition Metal-Nitrogen-Carbon Catalysts in Oxygen, Carbon Dioxide or Nitrogen Electro-Reduction". ECS Meeting Abstracts MA2022-01, nr 49 (7.07.2022): 2077. http://dx.doi.org/10.1149/ma2022-01492077mtgabs.
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Over the last two decades, platinum group metal-free (PGM-free) catalysts are attracting increasing attention and finding applications in several important process across many electrochemical energy technologies. Among those PGM-free materials, atomically dispersed (AD) transition metal-nitrogen-carbon (M-N-C) catalysts are gaining exceptional popularity as they demonstrate very high (for this class of materials) activity in oxygen reduction reaction (ORR)1 and are the only cathode catalysts suitable for both proton exchange membrane fuel cells (PEMFC) and alkaline, including anion/hydroxyl exchange membrane fuel cells (AFC, AEMFC/HEMFC). Over the last few years, M-N-C catalysts have shown promising activity in carbon dioxide reduction reaction (CO2RR).2 In this case, varying the transition metal in M-N-Cs opens routes for controlling the selectivity towards a list of C1 and C2 products. There are recent reports on catalytic activity of AD M-N-C materials in direct electro-reduction of molecular nitrogen (N2RR) or reactions of reduction of nitrates, nitrites or various nitrogen oxides (NOx). We have systematically investigated all these processes having as a base the M-N-C catalysts synthesized by sacrificial support method (SSM) – a hard template approach with transition metal salt and charge-transfer organic salt (nicarbazin) mixed by ball-milling, pyrolyzed at high temperature in inert atmosphere and then etched in HF after cooling. In most cases a secondary (similar) pyrolysis was performed to refine the material and ensure its AD character. The makeup and structure of the active site/sites of the AD M-N0C electrocatalysts, including geometry (coordination) and chemistry (composition and oxidation state) remain contentious to this day. There is an emerging agreement however, that the transition metal (at least for the 2nd row transitions meals) is immediately associated with (liganded by) the nitrogen functionalities, displayed on the surface if the carbonaceous substrate. It is almost universally accepted that N-coordinated AD transition metal ions, either as in-plane or edge-type defect in “graphene” sheet, are the main/principal active sites. This is often combined with a broadly accepted hypothesis that micro-porous surface area plays a critical role forming edge-type, intercalational active sites while meso-porous interface is most-likely associated with the in-plane, substitutional AD metal sites. Candidate structures participating in reativity towards O2, CO2 or nitrogen species include a list of nitrogen-containg and oxygen-containng moeties in the carbonaceous matrix. The carbon itself displays various degrees of graphitization, depending on the transition metal used in M-N-C synthesis. Additional complexity in this calss of caralysts study comes from the fact that many samples are not strictly AD materials. They often contain incorporated metal nano-particles, corresponding (native) oxides and/or carbides and nitrides (oxocabides and oxonitrides have been observed as well).These “unrefined” M-N-C materials are often used in practice and the corresponding nano-particle components of the de-facto nanocomposites do alter substantially the reactivity and selectivity of the catalysts in all these electro-reduction reactions. This talk discusses the mechanistic aspects of M-N-C catalysts in ORR, CO2RR, N2RR and electroreduction of nitrogen-containing oxo-species, obtained when cross-referencing electrochemical activity results obtained in rotating disk and rotating ring-disk electrodes setting (RDE/RRDE) with those observed in near-ambient pressure X-ray photo-electron spectroscopy (NAP-XPS) and supported by density functional theory calculations of the reagents adsorption on AD transition metal or nitrogen- or oxygen-containing moieties from the carbonaceous matrix of the M-N-Cs. The later are of particular importance as significant reactivity has been observed for most of those processes when metal-free, nitrogen-doped carbon (N-C) catalysts are used.3 We will present a case that outlines the reactivity of M-N-C in those important electro-reduction reactions in terms of (i) role of the AD transition metal, (ii) role of the surface N-groups as co-catalysts/alternative sites (iii) role of surface oxides as co-catalysts or hydrophilic/hydrophobic properties descriptor, the last being also critically dependent on morphology.4 References: T. Asset and P. Atanassov, Joule, 2020, 4, 33. T. Asset, S.T. Garcia, S. Herrera, N. Andersen, Y. Chen, E.J. Peterson, I. Matanovic, K.Artyushkova, J. Lee, S.D. Minteer,S. Dai, X. Pan, K. Chavan, S. Calabrese Bartonand P. Atanassov, ACS Catalysis, 2019, 9, 7668 D. Hursán, A. Samu,K. Artyushkova,T. Asset, P. Atanassov and C. Janáky, Joule, 2019, 3 1719 Y. Huang, Y. Chen, M. Xu, T. Asset, P. Tieu, A. Gili, D. Kulkarni, V. de Andrade, F. de Carlo, H. S. Barnard, A. Doran, D. Y. Parkinson, X. Pan, P. Atanassov, and I. Zenyuk, Materials Today, 2021, 47, 53.
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Myers, Deborah J., Ahmed A. Farghaly, Magali Ferrandon, A. Jeremy Kropf i David A. Cullen. "Platinum Group Metal-Free Oxygen Evolution Electrocatalysts for Alkaline Water Electrolysis". ECS Meeting Abstracts MA2022-02, nr 44 (9.10.2022): 1672. http://dx.doi.org/10.1149/ma2022-02441672mtgabs.
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The sluggish kinetics of oxygen electrocatalysis and the resulting high overpotentials necessary to achieve useful current densities limit the development of promising technologies, such as fuel cells, water, and carbon dioxide electrolyzers, and metal-oxygen batteries.1 The best catalysts for both the oxygen reduction and oxygen evolution reactions (ORR and OER, respectively) are based on precious, platinum group metals (PGMs), such as platinum and iridium, leading to limitations in the cost-effective implementation of these technologies.2,3 The development of alternative catalysts, with comparable or higher activity and durability to the PGM catalysts and derived from earth-abundant materials has thus been an active research area for decades. Incredible progress has been made in developing PGM-free electrocatalysts for the OER in alkaline environments, with perovskite oxides showing activities comparable to PGM-based catalysts.4,5 Perovskite oxides are a very broad class of materials with the general formula of ABO3, where the B site is occupied by smaller transition metal ions and the A site by larger cations which have 12-fold coordination with O.4 Both the A sites and B sites can be occupied by multiple metal ions, leading to an even more expansive design space for this class of materials. Another interesting class of catalysts is Fe and Ni oxides derived from the electrochemical oxidation of metal-organic frameworks (MOFs), with the advantages of this material over the perovskites being high electronic conductivity and high surface area. This presentation will describe the development and application of a high-throughput methodology to accelerate the exploration of the effects of composition and synthesis parameters on the activity of perovskite oxide and metal-organic framework-derived alkaline electrolyte OER catalysts. The evolution of the oxidation state and atomic structure of the MOF materials in the electrochemical environment, as determined using in situ X-ray absorption spectroscopy (XAS), as well as the evolution of the morphology of the catalyst, as determined using electron microscopy, will be described. References Yang, X. Han, A.I. Douka, L. Huang, L. Gong, C. Xia, H.S. Park, and B.Y. Xia, Adv. Func. Mater., 31 (2021) 2007602. Pivovar, Nature Catalysis, 2 (2019) 562. Thompson and D. Papageorgopoulos, Nature Catalysis, 2 (2019) 558. Hwang, R.R. Rao, L. Giordano, Y. Katayama, Y. Yu, and Y. Shao-Horn, Science 358 (2017) 751. Suntivich, K.J. May, H.A. Gasteiger, J.B. Goodenough, Y. Shao-Horn, Science, 334 (2011) 1383. Acknowledgements This work was supported by the U.S. Department of Energy (DOE), Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office (HFTO) under the auspices of the Electrocatalysis Consortium (ElectroCat 2.0). This work was also supported by DOE, Advanced Research Projects Agency-Energy (ARPA-E) under the DIFFERENTIATE program. This work utilized the resources of the Advanced Photon Source, a DOE Office of Science user facility operated by Argonne National Laboratory for DOE Office and was authored by Argonne, a DOE Office of Science laboratory operated for DOE by UChicago Argonne, LLC under contract no. DE-AC02-06CH11357.
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Sugrue, Elena, Nicholas J. Fraser, Davis H. Hopkins, Paul D. Carr, Jeevan L. Khurana, John G. Oakeshott, Colin Scott i Colin J. Jackson. "Evolutionary Expansion of the Amidohydrolase Superfamily in Bacteria in Response to the Synthetic Compounds Molinate and Diuron". Applied and Environmental Microbiology 81, nr 7 (30.01.2015): 2612–24. http://dx.doi.org/10.1128/aem.04016-14.
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ABSTRACTThe amidohydrolase superfamily has remarkable functional diversity, with considerable structural and functional annotation of known sequences. In microbes, the recent evolution of several members of this family to catalyze the breakdown of environmental xenobiotics is not well understood. An evolutionary transition from binuclear to mononuclear metal ion coordination at the active sites of these enzymes could produce large functional changes such as those observed in nature, but there are few clear examples available to support this hypothesis. To investigate the role of binuclear-mononuclear active-site transitions in the evolution of new function in this superfamily, we have characterized two recently evolved enzymes that catalyze the hydrolysis of the synthetic herbicides molinate (MolA) and phenylurea (PuhB). In this work, the crystal structures, mutagenesis, metal ion analysis, and enzyme kinetics of both MolA and PuhB establish that these enzymes utilize a mononuclear active site. However, bioinformatics and structural comparisons reveal that the closest putative ancestor of these enzymes had a binuclear active site, indicating that a binuclear-mononuclear transition has occurred. These proteins may represent examples of evolution modifying the characteristics of existing catalysts to satisfy new requirements, specifically, metal ion rearrangement leading to large leaps in activity that would not otherwise be possible.
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Mallamace, Domenico, Georgia Papanikolaou, Siglinda Perathoner, Gabriele Centi i Paola Lanzafame. "Comparing Molecular Mechanisms in Solar NH3 Production and Relations with CO2 Reduction". International Journal of Molecular Sciences 22, nr 1 (25.12.2020): 139. http://dx.doi.org/10.3390/ijms22010139.
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Molecular mechanisms for N2 fixation (solar NH3) and CO2 conversion to C2+ products in enzymatic conversion (nitrogenase), electrocatalysis, metal complexes and plasma catalysis are analyzed and compared. It is evidenced that differently from what is present in thermal and plasma catalysis, the electrocatalytic path requires not only the direct coordination and hydrogenation of undissociated N2 molecules, but it is necessary to realize features present in the nitrogenase mechanism. There is the need for (i) a multi-electron and -proton simultaneous transfer, not as sequential steps, (ii) forming bridging metal hydride species, (iii) generating intermediates stabilized by bridging multiple metal atoms and (iv) the capability of the same sites to be effective both in N2 fixation and in COx reduction to C2+ products. Only iron oxide/hydroxide stabilized at defective sites of nanocarbons was found to have these features. This comparison of the molecular mechanisms in solar NH3 production and CO2 reduction is proposed to be a source of inspiration to develop the next generation electrocatalysts to address the challenging transition to future sustainable energy and chemistry beyond fossil fuels.
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Xuemei Yang and Xiaohua Wang, Xuemei Yang and Xiaohua Wang. "Reduction Reactions of CO2 on Rutile TiO2 (110) Nanosheet via Coordination Activation". Journal of the chemical society of pakistan 44, nr 6 (2022): 576. http://dx.doi.org/10.52568/001180/jcsp/44.06.2022.
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Based on the previous coordination catalysis theory, the active site on the surface of transition metal oxides can activate the CO2 molecule. Ultrathin two-dimensional (2D) rutile TiO2 nanosheet with (110) crystal face as the main exposed surface has many active sites of Ti3+ and O vacancy, which have some synergistic effects to greatly reduce the dissociation energy of CO2. Following previous assumptions, four possible reduction processes of CO2 on rutile TiO2 (110) surface were systematically assessed by density functional theory (DFT) simulations. The reduction reactions of CO2 along I faces difficultly in proceeding due to the relatively weak interaction between CO2 and the active surface. Additionally, along III, the adsorption configuration of CO2 in the pristine state has huge distinctions with the model that suggests that the defined route is unlikely to occur on the rutile TiO2 (110) surface. However, through carefully comparing the energy differences as well as transition state searching, the reduction reaction along II has a high probability of finishing and finally generating HCOOH on the surface owing to the minimal energy differences and low activation barrier. Furthermore, the reduction reaction of CO2 to CH4 guided along IV is predicted to more easily take place with the assistance of O vacancy on the active surface. The synergistic action among Ti3+ site, O vacancy, and H+ can aid in fixing molecular CO2 by breaking the strong bond of C=O in CO2 and generating different fuels via coordination activation. This work will not only provide strong theoretical support to previous assumptions but can also lighten the routes to explore more active catalysis towards the reduction of CO2.
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Liu, He, Daniel Grasseschi, Akhil Dodda, Kazunori Fujisawa, David Olson, Ethan Kahn, Fu Zhang i in. "Spontaneous chemical functionalization via coordination of Au single atoms on monolayer MoS2". Science Advances 6, nr 49 (grudzień 2020): eabc9308. http://dx.doi.org/10.1126/sciadv.abc9308.
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Surface functionalization of metallic and semiconducting 2D transition metal dichalcogenides (TMDs) have mostly relied on physi- and chemi-sorption at defect sites, which can diminish the potential applications of the decorated 2D materials, as structural defects can have substantial drawbacks on the electronic and optoelectronic characteristics. Here, we demonstrate a spontaneous defect-free functionalization method consisting of attaching Au single atoms to monolayers of semiconducting MoS2(1H) via S-Au-Cl coordination complexes. This strategy offers an effective and controllable approach for tuning the Fermi level and excitation spectra of MoS2 via p-type doping and enhancing the thermal boundary conductance of monolayer MoS2, thus promoting heat dissipation. The coordination-based method offers an effective and damage-free route of functionalizing TMDs and can be applied to other metals and used in single-atom catalysis, quantum information devices, optoelectronics, and enhanced sensing.
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Wang, Jing, Heng Kong, Haihong Zhong, Yu Jiang, Fei Guo, Nicolas Alonso-Vante i Yongjun Feng. "Recent Progress on Transition Metal Based Layered Double Hydroxides Tailored for Oxygen Electrode Reactions". Catalysts 11, nr 11 (18.11.2021): 1394. http://dx.doi.org/10.3390/catal11111394.
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The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), namely, so-called oxygen electrode reactions, are two fundamental half-cell reactions in the energy storage and conversion devices, e.g., zinc–air batteries and fuel cells. However, the oxygen electrode reactions suffer from sluggish kinetics, large overpotential and complicated reaction paths, and thus require efficient and stable electrocatalysts. Transition-metal-based layered double hydroxides (LDHs) and their derivatives have displayed excellent catalytic performance, suggesting a major contribution to accelerate electrochemical reactions. The rational regulation of electronic structure, defects, and coordination environment of active sites via various functionalized strategies, including tuning the chemical composition, structural architecture, and topotactic transformation process of LDHs precursors, has a great influence on the resulting electrocatalytic behavior. In addition, an in-depth understanding of the structural performance and chemical-composition-performance relationships of LDHs-based electrocatalysts can promote further rational design and optimization of high-performance electrocatalysts. Finally, prospects for the design of efficient and stable LDHs-based materials, for mass-production and large-scale application in practice, are discussed.
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Thompson, Laurence K. "2004 Alcan Award LectureFrom dinuclear to triakontahexanuclear complexes Adventures in supramolecular coordination chemistry". Canadian Journal of Chemistry 83, nr 2 (1.02.2005): 77–92. http://dx.doi.org/10.1139/v04-173.
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Polynuclear coordination complexes result from the interplay between the arrangement of the binding sites of a ligand, and their donor content, and the coordination preferences of the metal ion involved. Rational control of the ligand properties, such as denticity, geometry, and size, can lead to large, and sometimes predictable, polynuclear assemblies. This Alcan Award Lecture highlights our "adventures" with polynucleating ligands over the last 25 years, with examples ranging from simple dinucleating to more exotic high-denticity ligands. Complexes with nuclearities ranging from 2 to 36 have been produced, many of which have novel magnetic, electrochemical, and spectroscopic properties. Self-assembly strategies using relatively simple "polytopic" ligands have been very successful in producing high-nuclearity clusters in high yield. For example, linear "tritopic" ligands produce M9 (M = Mn(II), Fe(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II)) [3 × 3], flat grid-like molecules, which have quantum dot-like arrays of nine closely spaced metal centers in electronic communication. Some of these grids are discussed in terms of their novel magnetic and electrochemical properties, and also as multistable nanometer-scale platforms for potential molecular device behaviour. Bigger ligands with extended arrays of coordination pockets, and the capacity to self-assemble into much larger grids, are highlighted to illustrate our current and longer term goals of generating polymetallic molecular two-dimensional layers on surfaces.Key words: Alcan Award Lecture, transition metal, polynuclear, structure, magnetism, electrochemistry, surface studies, molecular device.
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Vetting, Matthew W., Lawrence P. Wackett, Lawrence Que, John D. Lipscomb i Douglas H. Ohlendorf. "Crystallographic Comparison of Manganese- and Iron-Dependent Homoprotocatechuate 2,3-Dioxygenases". Journal of Bacteriology 186, nr 7 (1.04.2004): 1945–58. http://dx.doi.org/10.1128/jb.186.7.1945-1958.2004.
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ABSTRACT The X-ray crystal structures of homoprotocatechuate 2,3-dioxygenases isolated from Arthrobacter globiformis and Brevibacterium fuscum have been determined to high resolution. These enzymes exhibit 83% sequence identity, yet their activities depend on different transition metals, Mn2+ and Fe2+, respectively. The structures allow the origins of metal ion selectivity and aspects of the molecular mechanism to be examined in detail. The homotetrameric enzymes belong to the type I family of extradiol dioxygenases (vicinal oxygen chelate superfamily); each monomer has four βαβββ modules forming two structurally homologous N-terminal and C-terminal barrel-shaped domains. The active-site metal is located in the C-terminal barrel and is ligated by two equatorial ligands, H214NE1 and E267OE1; one axial ligand, H155NE1; and two to three water molecules. The first and second coordination spheres of these enzymes are virtually identical (root mean square difference over all atoms, 0.19 Å), suggesting that the metal selectivity must be due to changes at a significant distance from the metal and/or changes that occur during folding. The substrate (2,3-dihydroxyphenylacetate [HPCA]) chelates the metal asymmetrically at sites trans to the two imidazole ligands and interacts with a unique, mobile C-terminal loop. The loop closes over the bound substrate, presumably to seal the active site as the oxygen activation process commences. An “open” coordination site trans to E267 is the likely binding site for O2. The geometry of the enzyme-substrate complexes suggests that if a transiently formed metal-superoxide complex attacks the substrate without dissociation from the metal, it must do so at the C-3 position. Second-sphere active-site residues that are positioned to interact with the HPCA and/or bound O2 during catalysis are identified and discussed in the context of current mechanistic hypotheses.
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He, Yanghua, John Christian Weiss i Piotr Zelenay. "Me-N-C Electrocatalysts for Electrochemical CO2 Reduction to High-Value Products". ECS Meeting Abstracts MA2022-02, nr 54 (9.10.2022): 2016. http://dx.doi.org/10.1149/ma2022-02542016mtgabs.
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The development of sustainable carbon-neutral energy technologies to mitigate greenhouse gas emissions has become imperative and urgent. Of special interest and importance in this context is the use of electricity from intermittent renewable energy sources (wind, solar) for electrochemical conversion of carbon dioxide (CO2) to easily storable and transportable value-added products: fuels and feedstock chemicals. Nanoparticles of non-precious metals, e.g., Cu, Sn, Co, show high activity for electrochemical CO2 reduction reaction (CO2RR) but suffer from poor selectivity, resulting in a mixture of products that require tedious and costly separation. Recently, transition metal- and nitrogen-doped carbon (Me-N-C) materials have been emerged as promising CO2RR catalysts thanks to their well-defined structures and good activity. However, their selectivity, while respectable for the generation of carbon monoxide (CO), is low for high energy-content products. A limited understanding of reaction pathways and degradation mechanism of Me-N-C catalysts for CO2RR has additionally stemmed a rational design of these materials. In this presentation, we summarize our study of the activity, selectivity, and stability of Me-N-C (Me = Fe, Co, Ni, or Cu, etc.) catalysts for the CO2RR, focusing on the role of the local coordination environment at metal centers and metal-carbon substrate interactions. We also report the obtained bimetallic M1M2-N-C catalysts, designed to enable the formation of multi-carbon products through CO2RR and utilizing high surface-area three-dimensional carbon matrix as support for metal sites with improved CO2RR activity. The main objective of this work is to use Me-N-C catalysts to produce high energy-density chemicals, enhance mechanistic understanding, and bring CO2RR closer to practical applications.
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Yahsi, Yasemin. "X-ray characterization and magnetic properties of dioxygen-bridged CuIIand MnIIISchiff base complexes". Acta Crystallographica Section C Structural Chemistry 72, nr 7 (24.06.2016): 585–92. http://dx.doi.org/10.1107/s2053229616008974.
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The coordination chemistry of multinuclear metal compounds is important because of their relevance to the multi-metal active sites of various metalloproteins and metalloenzymes. Multinuclear CuIIand MnIIIcompounds are of interest due to their various properties in the fields of coordination chemistry, inorganic biochemistry, catalysis, and optical and magnetic materials. Oxygen-bridged binuclear MnIIIcomplexes generally exhibit antiferromagnetic interactions and a few examples of ferromagnetic interactions have also been reported. Binuclear CuIIcomplexes are important due to the fact that they provide examples of the simplest case of magnetic interaction involving only two unpaired electrons. Two novel dioxygen-bridged copper(II) and manganese(III) Schiff base complexes, namely bis(μ-4-bromo-2-{[(3-oxidopropyl)imino]methyl}phenolato)dicopper(II), [Cu2(C10H10BrNO2)2], (1), and bis(diaqua{4,4′-dichloro-2,2′-[(1,1-dimethylethane-1,2-diyl)bis(nitrilomethanylylidene)]diphenolato}manganese(III)) bis{μ-4,4′-dichloro-2,2′-[(1,1-dimethylethane-1,2-diyl)bis(nitrilomethanylylidene)]diphenolato}bis[aquamanganese(III)] tetrakis(perchlorate) ethanol disolvate, [Mn(C18H16Cl2N2O2)(H2O)2]2[Mn2(C18H16Cl2N2O2)2(H2O)2](ClO4)4·2C2H5OH, (2), have been synthesized and single-crystal X-ray diffraction has been used to analyze their crystal structures. The structure analyses of (1) and (2) show that each CuIIatom is four-coordinated, with long weak Cu...O interactions of 2.8631 (13) Å linking the dinuclear halves of the centrosymmetric tetranucelar molecules, while each MnIIIatom is six-coordinated. The shortest intra- and intermolecular nonbonding Mn...Mn separations are 3.3277 (16) and 5.1763 (19) Å for (2), while the Cu...Cu separations are 3.0237 (3) and 3.4846 (3) Å for (1). The magnetic susceptibilities of (1) and (2) in the solid state were measured in the temperature range 2–300 K and reveal the presence of antiferromagnetic spin-exchange interactions between the transition metal ions.
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Zhou, Quan, Yang Hu, Benedikt Axel Brandes, Lars Cleemann, Jens Oluf Jensen i Qingfeng Li. "Synthesis of Platinum-Rare Earth Metal Alloy Catalysts for Proton Exchange Membrane Fuel Cells". ECS Meeting Abstracts MA2022-01, nr 35 (7.07.2022): 1451. http://dx.doi.org/10.1149/ma2022-01351451mtgabs.
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Electrocatalysts for low temperature fuel cells are based on noble metals and can be promoted by development of alloys of platinum with e.g. late transition metals such as Ni and Co.[1,2] It has been reported that Pt alloys with rare earth (RE) metals exhibit remarkable activity and high stability towards the oxygen reduction reaction.[3] Due to the very low standard reduction potentials and high oxophilicity of rare earth metals, preparation platinum alloys in form of nanoparticles meets great challenges for chemical routes of co-reduction. A one-step method is recently developed to prepare Pt−RE nanoalloys from a mixture of solid state precursors consisting of metal halides in their hydrate forms, a suitable nitrogen-rich compound and a carbon support.[4,5] The synthesis involves in situ formation of a carbon-nitrogen network, onto which the two metals are atomically dispersed. The coordination with nitrogen sites stabilizes the metals, which, upon thermal decomposition under a mild reducing atmosphere, leads to the formation of Pt-RE nanoalloys. The carbon support is introduced either as carbon blacks or carbon supported platinum powder. The pre-formed, either in or ex situ, platinum nanoparticles, facilitates the reduction of rare earth metals thermodynamically driven by the negative alloying free energy. A series of pure crystal phases such as Pt5RE (e.g. La, Ce, Nd), and Pt3RE (e.g. Y, Gd, Tb) have been synthesized in form of carbon supported nanoparticles with tunable metal loadings and alloy particle sizes. One of the typical catalysts is the Pt5Ce/C in a metal to carbon ratio of 30 wt% and an average alloy particle size of ca. 5.5 nm which exhibits an area specific activity of 3.7 times and a mass activity of 1.9 times higher than those of the Pt/C analogue. Further understanding and improvement of the process are in progress and the updated results will be presented in this talk. [1]. J. K. Norskov et al., Nature Chemistry 1, 37-46 (2009) [2]. X. Q. Huang et al., Science 348, 1230-1234 (2015) [3]. M. Escudero-Escribano et al., Science 352, 73-76 (2016) [4]. Y. Hu et al., J. Am. Chem. Soc. 142, 953–961 (2020) [5]. Y. Hu et al., Chem. Mater. 33, 2, 535–546 (2021)
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Kulesza, Pawel J., Beata Rytelewska, Iwona A. Rutkowska, Karolina Sobkowicz, Anna Chmielnicka, Takwa Chouki i Saim Emin. "(Invited) Electroreduction of Nitrogen to Ammonia at Iron Catalytic Sites Generated at Interfaces Utilizing Iron Phosphides and Heme-Type Complexes". ECS Meeting Abstracts MA2022-02, nr 48 (9.10.2022): 1803. http://dx.doi.org/10.1149/ma2022-02481803mtgabs.
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The feasibility of performing nitrogen electroreduction reaction, or nitrogen fixation, particularly in aqueous solutions, constitutes an attractive prospect to produce ammonia under ambient, or near ambient, conditions. Development of durable, specific and reasonably efficient low-cost catalysts remains a great challenge for electrochemical science and technology. Currently, most of electrochemical approaches to N2-fixation suffers from slow kinetics due to the difficulty of achieving the appropriate adsorption and activation of dinitrogen leading to cleavage of the strong, triple N≡N bond. This symposium will feature presentations on research dealing with the fundamental and applied aspects of nitrogen reduction reactions of relevance various aspects of science and existing technologies. Transition metal phosphides are promising non-noble earth-abundant catalysts with broad electrocatalytic properties, in particular when it comes to electroreduction of such inert reactants as carbon dioxide. Herein, we report the successful electrocatalytic reduction of nitrogen (N2) using different phases of iron phosphide activated at 450 °C. For example, the FeP and Fe2P phases have been found to act as efficient catalysts for the formation of NH3 in alkaline and semineutral media. Detection of in-situ formed product has been achieved by probing the electrooxidation of NH3 to nitrogen (N2) using the additional working electrode modified with Pt nanoparticles. On mechanistic grounds, the iron (Fe0) sites seem to be electrocatalytic active during the reduction of nitrogen The iron sites can also be generated within the porphyrin rings and related coordination structures. Their high electrocatalytic activity was historically demonstrated for the CO2-reduction. The results obtained here indicate the feasibility of horseradish peroxidase (HRP) to act as the biocatalyst, when deposited on the glassy carbon (an inert electrode substrate), capable of inducing electroduction of not only CO2 but also N2. HRP is a metalloenzyme, in which a large alpha-helical protein which binds heme as a redox cofactor. The actual electrocatalytic properties shall be attributed to the existence of heme groups, i.e. complexes of iron ions coordinated to porphyrin units. On mechanistic grounds, the nitrogen molecules seems to be chemisorbed or attracted to the heme centers during the activation step. Indeed, only “adsorbates” of N2 are catalytically reduced. In other words, the HRP-surface-attached N2 molecules, rather than the bulk reactant, are reduced at the electrocatalytic interface. The reduction reaction of nitrogen is a multielectron and multiproton transfer process suffering from high over-potentials and limited selectivity The N2 molecule with triple bond requires special means of activation through strong adsorption at the electrocatalytic interface. Obviously most of electrocatalysts will be more active toward hydrogen evolution than ammonia production. Consequently, ammonia is produced at trace levels, and the reaction efficiency is very low. On the whole, the presence of the α-helix HRP secondary structure (composed of backbone N−H groups that hydrogen-bonded to the backbone C=O groups of the amino acid network) is likely to contribute to the system’s good stability and selectivity (e.g., with respect to the competing hydrogen evolution reaction).
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Hestericová, Martina, Tillmann Heinisch, Markus Lenz i Thomas R. Ward. "Ferritin encapsulation of artificial metalloenzymes: engineering a tertiary coordination sphere for an artificial transfer hydrogenase". Dalton Transactions 47, nr 32 (2018): 10837–41. http://dx.doi.org/10.1039/c8dt02224k.
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Huang, Tiefan, Guan Sheng, Priyanka Manchanda, Abdul H. Emwas, Zhiping Lai, Suzana Pereira Nunes i Klaus-Viktor Peinemann. "Cyclodextrin polymer networks decorated with subnanometer metal nanoparticles for high-performance low-temperature catalysis". Science Advances 5, nr 11 (listopad 2019): eaax6976. http://dx.doi.org/10.1126/sciadv.aax6976.
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The synthesis of support materials with suitable coordination sites and confined structures for the controlled growth of ultrasmall metal nanoparticles is of great importance in heterogeneous catalysis. Here, by rational design of a cross-linked β-cyclodextrin polymer network (CPN), various metal nanoparticles (palladium, silver, platinum, gold, and rhodium) of subnanometer size (<1 nm) and narrow size distribution are formed via a mild and facile procedure. The presence of the metal coordination sites and the network structure are key to the successful synthesis and stabilization of the ultrasmall metal nanoparticles. The as-prepared CPN, loaded with palladium nanoparticles, is used as a heterogeneous catalyst and shows outstanding catalytic performance in the hydrogenation of nitro compounds and Suzuki-Miyaura coupling reaction under mild conditions. The CPN support works synergistically with the metal nanoparticles, achieving high catalytic activity and selectivity. In addition, the catalytic activity of the formed catalyst is controllable.
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Huang, Yanmin, Zhuo Ma, Yunxia Hu, Dongfeng Chai, Yunfeng Qiu, Guanggang Gao i PingAn Hu. "An efficient WSe2/Co0.85Se/graphene hybrid catalyst for electrochemical hydrogen evolution reaction". RSC Advances 6, nr 57 (2016): 51725–31. http://dx.doi.org/10.1039/c6ra08618g.
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Transition metal doped layered transition metal dichalcogenides (TMDs) are regarded as promising hydrogen evolution reaction (HER) candidates due to exposed active sites at both edges and basal planes.
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Shi, Hang, Qi-Kai Kang, Yunzhi Lin i Yuntong Li. "Transition-Metal-Catalyzed Amination of Aryl Fluorides". Synlett 31, nr 12 (14.05.2020): 1135–39. http://dx.doi.org/10.1055/s-0040-1707118.
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Arene activation via transition-metal (TM) η6-coordination has merged as a powerful method to diversify the aromatic C–F bond, which is relatively less reactive due to its high bond energy. However, this strategy in general requires to use largely excess arenes or TM η6-complexes as the substrates. Herein, we highlight our recent work on the catalytic SNAr amination of electron-rich and electron-neutral aryl fluorides that are inert in classical SNAr reactions. This protocol enabled by a Ru/hemilabile ligand catalyst covers a broad scope of substrates without wasting arenes. Mechanistic studies revealed that the nucleophilic substitution proceeded on a Ru η6-arene complex, and the hemilabile ligand significant promoted the arene dissociation.
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Zaremba, Roman, Ute Ch Rodewald, Vasyl’ I. Zaremba i Rainer Pöttgen. "Transition Metal-Indium Substitution in Y3Rh2-type Compounds". Zeitschrift für Naturforschung B 62, nr 11 (1.11.2007): 1397–406. http://dx.doi.org/10.1515/znb-2007-1108.
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New rare earth metal-rich indium compounds RE3T2−xInx (RE = Gd, Tb, Dy, Ho, Er, Tm; T = Rh, Pd, Ir) were synthesized from the elements via high-frequency melting and subsequent annealing in sealed silica ampoules. These intermetallics crystallize with substitution variants of the tetragonal Y3Rh2-type structure, space group I4/mcm, Z = 28. All samples were studied by powder and single crystal X-ray diffraction: a = 1164.2(2), c = 2486.5(5) pm, for Tb3Rh1.25In0.71, a = 1139.4(2), c = 2480.8(5) pm for Er3Rh1.48In0.52, a = 1153.7(2), c = 2465.4(5) pm for Tm3Rh1.25In0.71, a = 1146.4(2), c = 2498.4(5) pm for Tb3Ir1.62In0.33, a = 1154.9(2), c = 2500.1(5) pm for Tb3Ir1.52In0.44, a = 1187.8(2), c = 2559.2(5) pm for Gd3Pd1.27In0.71, and a = 1169.1(2), c = 2530.3(5) pm for Ho3Pd1.27In0.71. The indium atoms show different site occupancies on the transition metal positions, and for most crystals small defects occur for one transition metal site. Gd3Rh1.30In0.64 (a = 1166.3(2), c = 2512.0(5) pm) and Dy3Rh1.31In0.64 reveal complete rhodium-indium ordering. These two indides crystallize with the translationengleiche subgroup I4/m. The rare earth atoms in these RE3T2−xInx indides have coordination numbers between 13 and 15. A striking structural motif is the tetrahedral indium coordination in the first coordination sphere of the RE5 position (305 pm Gd-In in Gd3Rh1.30In0.64). The transition metal atoms show trigonal prismatic or square anti-prismatic rare earth coordination. In all compounds investigated, the indium atoms substitute these metals only at the square prismatic sites and at one site of coordination number 10. The crystal chemical consequences of the different ordered and statistical transition metal-indium substitutions are discussed
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Sellmann, Dieter, Michael Geck, Falk Knoch, Gerhard Ritter i Joachim Dengler. "Transition-metal complexes with sulfur ligands. 57. Stabilization of high-valent iron(IV) centers and vacant coordination sites by sulfur .pi.-donation: syntheses, x-ray structures, and properties of [Fe("S2")2(PMe3)n] (n = 1, 2) and (NMe4)[Fe("S2")2(PMe3)2].cntdot.CH3OH ("S2"2- = 1,2-benzenedithiolate(2-))". Journal of the American Chemical Society 113, nr 10 (maj 1991): 3819–28. http://dx.doi.org/10.1021/ja00010a026.
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Wei, Shice, Fan Zhang, Zhenying Chen, Junjie Ding, Bai Xue i Chenbao Lu. "Porous carbons embedded with nitrogen-coordinated cobalt as an exceptional electrochemical catalyst for high-performance Zn–air batteries". New Journal of Chemistry 44, nr 29 (2020): 12850–56. http://dx.doi.org/10.1039/d0nj02933e.
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Huxley, Michael T., Campbell J. Coghlan, Witold M. Bloch, Alexandre Burgun, Christian J. Doonan i Christopher J. Sumby. "X-ray crystallographic insights into post-synthetic metalation products in a metal–organic framework". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 375, nr 2084 (13.01.2017): 20160028. http://dx.doi.org/10.1098/rsta.2016.0028.
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Post-synthetic modification of metal–organic frameworks (MOFs) facilitates a strategic transformation of potentially inert frameworks into functionalized materials, tailoring them for specific applications. In particular, the post-synthetic incorporation of transition-metal complexes within MOFs, a process known as ‘metalation’, is a particularly promising avenue towards functionalizing MOFs. Herein, we describe the post-synthetic metalation of a microporous MOF with various transition-metal nitrates. The parent framework, 1 , contains free-nitrogen donor chelation sites, which readily coordinate metal complexes in a single-crystal to single-crystal transformation which, remarkably, can be readily monitored by X-ray crystallography. The presence of an open void surrounding the chelation site in 1 prompted us to investigate the effect of the MOF pore environment on included metal complexes, particularly examining whether void space would induce changes in the coordination sphere of chelated complexes reminiscent of those found in the solution state. To test this hypothesis, we systematically metalated 1 with first-row transition-metal nitrates and elucidated the coordination environment of the respective transition-metal complexes using X-ray crystallography. Comparison of the coordination sphere parameters of coordinated transition-metal complexes in 1 against equivalent solid- and solution-state species suggests that the void space in 1 does not markedly influence the coordination sphere of chelated species but we show notably different post-synthetic metalation outcomes when different solvents are used. This article is part of the themed issue ‘Coordination polymers and metal–organic frameworks: materials by design’.
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Kim, Hyo-Sub, Su-Gyung Lee, Young-Ho Kim, Dong-Hee Lee, Jin-Bae Lee i Chu-Sik Park. "Improvement of Lifetime Using Transition Metal-Incorporated SAPO-34 Catalysts in Conversion of Dimethyl Ether to Light Olefins". Journal of Nanomaterials 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/679758.
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Transition metal (Mn, Fe, or Ni) incorporated SAPO-34 (MeAPSO-34) nanocatalysts were synthesized using a hydrothermal method to improve the catalytic lifetime in the conversion of dimethyl ether to light olefins (DTO). The structures of the synthesized catalysts were characterized using several methods including XRD, SEM, BET,29Si-MAS NMR, and NH3-TPD techniques. Although the structure of the MeAPSO-34 catalysts was similar to that of the SAPO-34 catalyst, the amount of weak acid sites in all MeAPSO-34 catalysts was markedly increased and accompanied by differences in crystallinity and structural arrangement. The amount of weak acid sites decreased in the following order: NiAPSO-34 > FeAPSO-34 > MnAPSO-34 > SAPO-34 catalyst. The MeAPSO-34 catalysts, when used in the DTO reaction, maintained DME conversion above 90% for a longer time than the SAPO-34 catalyst, while also maintaining the total selectivity above 95% for light olefins. In addition, the NiAPSO-34 catalyst showed the longest catalytic lifetime; the lifetime was extended approximately 2-fold relative to the SAPO-34 catalyst. Therefore, the increase in the catalytic lifetime is related to the amount of weak acidic sites, and these sites are increased in number by incorporating transition metals into the SAPO-34 catalyst.
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Klahn, Marcus, i Torsten Beweries. "Organometallic water splitting – from coordination chemistry to catalysis". Reviews in Inorganic Chemistry 34, nr 3 (1.10.2014): 177–98. http://dx.doi.org/10.1515/revic-2013-0019.
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AbstractThis review gives an overview on the recent developments in the field of coordination chemistry of water at transition metal centres, which could give implications for a better understanding of the elementary steps of light-driven overall water splitting. Additionally, selected examples for homogeneous catalyst systems that are capable of producing hydrogen and/or oxygen from water are presented, focussing on the mechanistic aspects of water reduction and water oxidation.
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Zygiel, Emily M., i Elizabeth M. Nolan. "Transition Metal Sequestration by the Host-Defense Protein Calprotectin". Annual Review of Biochemistry 87, nr 1 (20.06.2018): 621–43. http://dx.doi.org/10.1146/annurev-biochem-062917-012312.
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In response to microbial infection, the human host deploys metal-sequestering host-defense proteins, which reduce nutrient availability and thereby inhibit microbial growth and virulence. Calprotectin (CP) is an abundant antimicrobial protein released from neutrophils and epithelial cells at sites of infection. CP sequesters divalent first-row transition metal ions to limit the availability of essential metal nutrients in the extracellular space. While functional and clinical studies of CP have been pursued for decades, advances in our understanding of its biological coordination chemistry, which is central to its role in the host–microbe interaction, have been made in more recent years. In this review, we focus on the coordination chemistry of CP and highlight studies of its metal-binding properties and contributions to the metal-withholding innate immune response. Taken together, these recent studies inform our current model of how CP participates in metal homeostasis and immunity, and they provide a foundation for further investigations of a remarkable metal-chelating protein at the host–microbe interface and beyond.
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Suo, Hongyi, Zisheng Zhang, Rui Qu, Yanan Gu i Yusheng Qin. "Tunable Late-Transition-Metal-Catalyzed Polymerization for Controlled Polymer Synthesis". Catalysts 13, nr 4 (29.03.2023): 670. http://dx.doi.org/10.3390/catal13040670.
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As a powerful protocol for the preparation of common polymers, such as polyolefins, polyesters, and polycarbonates, late-transition-metal-catalyzed polymerization can be carried out by controlling the reaction conditions or developing dynamic catalytic systems that use external stimuli to influence the performance of the active sites, resulting in well-defined polymeric materials. In particularly, under the latter conditions, ‘one catalyst’ can provide more than one kind of polymer with a controlled sequence from the monomer mixture, making full use of the prepared catalyst. In this review, tunable modes, including reaction conditions, redox, light or electrochemical properties, Lewis acids, and alkali metal cations, of late-transition-metal-complex (especially iron, cobalt, and nickel)-catalyzed polymerization were collected and thoroughly discussed.
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Shen, Mengxia, Hao Yang, Qingqing Liu, Qianyu Wang, Jun Liu, Jiale Qi, Xinyu Xu, Jiahua Zhu, Lilong Zhang i Yonghao Ni. "Competitive Coordination-Oriented Monodispersed Cobalt Sites on a N-Rich Porous Carbon Microsphere Catalyst for High-Performance Zn−Air Batteries". Nanomaterials 13, nr 8 (10.04.2023): 1330. http://dx.doi.org/10.3390/nano13081330.
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Metal/nitrogen-doped carbon single-atom catalysts (M−N−C SACs) show excellent catalytic performance with a maximum atom utilization and customizable tunable electronic structure. However, precisely modulating the M−Nx coordination in M−N−C SACs remains a grand challenge. Here, we used a N-rich nucleobase coordination self-assembly strategy to precisely regulate the dispersion of metal atoms by controlling the metal ratio. Meanwhile, the elimination of Zn during pyrolysis produced porous carbon microspheres with a specific surface area of up to 1151 m2 g−1, allowing maximum exposure of Co−N4 sites and facilitating charge transport in the oxygen reduction reaction (ORR) process. Thereby, the monodispersed cobalt sites (Co−N4) in N-rich (18.49 at%) porous carbon microspheres (CoSA/N−PCMS) displayed excellent ORR activity under alkaline conditions. Simultaneously, the Zn−air battery (ZAB) assembled with CoSA/N−PCMS outperformed Pt/C+RuO2-based ZABs in terms of power density and capacity, proving that they have good prospects for practical application.
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Din, Naseem Ud, Duy Le i Talat S. Rahman. "Computational screening of chemically active metal center in coordinated dipyridyl tetrazine network". Journal of Physics: Condensed Matter 35, nr 15 (17.02.2023): 154001. http://dx.doi.org/10.1088/1361-648x/acb8f3.
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Abstract Creation, stabilization, characterization, and control of single transition metal (TM) atoms may lead to significant advancement of the next-generation catalyst. Metal organic network (MON) in which single TM atoms are coordinated and separated by organic ligands is a promising class of material that may serve as a single atom catalyst. Our density functional theory-based calculations of MONs in which dipyridyl tetrazine (DPTZ) ligands coordinate with a TM atom to form linear chains leads to two types of geometries of the chains. Those with V, Cr, Mo, Fe, Co, Pt, or Pd atoms at the coordination center are planar while those with Au, Ag, Cu, or Ni are non-planar. The formation energies of the chains are high (∼2.0–7.9 eV), suggesting that these MON can be stabilized. Moreover, the calculated adsorption energies of CO and O2 on the metal atom at center of the chains with the planar configuration lie in the range 1.0–3.0 eV for V, Cr, Mo, Fe, and Co at the coordination center, paving the way for future studies of CO oxidation on TM-DPTZ chains with the above five atoms at the coordination center.
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Sellmann, Dieter, Michael Geck, Falk Knoch, Gerhard Ritter i Joachim Dengler. "Transition-metal complexes with sulfur ligands. 57. Stabilization of high-valent iron(IV) centers and vacant coordination sites by sulfur .pi.-donation: syntheses, x-ray structures, and properties of [Fe("S2")2(PMe3)n] (n = 1, 2) and (NMe4)[Fe("S2")2-(PMe3)2].cntdot.CH3OH ("S2"2- = 1,2-benzenedithiolate (2-)). [Erratum to document cited in CA114(22):220083s]". Journal of the American Chemical Society 114, nr 7 (marzec 1992): 2769. http://dx.doi.org/10.1021/ja00033a091.
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Bayach, Imene, Sehrish Sarfaraz, Nadeem S. Sheikh, Kawther Alamer, Nadiah Almutlaq i Khurshid Ayub. "Hydrogen Dissociation Reaction on First-Row Transition Metal Doped Nanobelts". Materials 16, nr 7 (31.03.2023): 2792. http://dx.doi.org/10.3390/ma16072792.
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Zigzag molecular nanobelts have recently captured the interest of scientists because of their appealing aesthetic structures, intriguing chemical reactivities, and tantalizing features. In the current study, first-row transition metals supported on an H6-N3-belt[6]arene nanobelt are investigated for the electrocatalytic properties of these complexes for the hydrogen dissociation reaction (HDR). The interaction of the doped transition metal atom with the nanobelt is evaluated through interaction energy analysis, which reveals the significant thermodynamic stability of TM-doped nanobelt complexes. Electronic properties such as frontier molecular orbitals and natural bond orbitals analyses are also computed, to estimate the electronic perturbation upon doping. The highest reduction in the HOMO–LUMO energy gap compared to the bare nanobelt is seen in the case of the Zn@NB catalyst (4.76 eV). Furthermore, for the HDR reaction, the Sc@NB catalyst displays the best catalytic activity among the studied catalysts, with a hydrogen dissociation barrier of 0.13 eV, whereas the second-best catalytic activity is observed for the Zn@NB catalyst (0.36 eV). It is further found that multiple active sites, i.e., the presence of the metal atom and nitrogen atom moiety, help to facilitate the dissociation of the hydrogen molecule. These key findings of this study enhance the understanding of the relative stability, electronic features, and catalytic bindings of various TM@NB catalysts.
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Nasch, Tono, Wolfgang Jeitschko i Ute Ch Rodewald. "Ternary Rare Earth Transition Metal Zinc Compounds RT2Zn20 with T = Fe, Ru, Co, Rh, and Ni". Zeitschrift für Naturforschung B 52, nr 9 (1.09.1997): 1023–30. http://dx.doi.org/10.1515/znb-1997-0901.
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Forty eight new compounds RT2Zn20 were prepared by annealing cold-pressed pellets of the elemental components in an argon atmosphere. They crystallize with the cubic CeCr2Al20 type structure (Fd3̅̅m , Z = 8), which was refined from single-crystal diffractometer data of TbFeiZn20 (a = 1411.1(1) pm ), YRu2Zn20 (a = 1422.6(1) pm ), DyRu2Zn20 (a = 1422.1(1) pm), GdCo2Zn20 (a = 1406.0(1) pm ), DyRh2Zn20 (a = 1418.2(1) pm ), and TmNi2Zn20 (a= 1401.6(1) pm) to conventional residuals varying betw een R = 0.011 and R - 0.024. The com pounds have a tendency for tw inning, thus m im icking hexagonal sym metry, with the cubic [111] axis as the axis w ith the pseudohexagonal symmetry. M inor inconsistencies in the cell volum es of these com pounds indicate slight deviations from the ideal com position. N evertheless, the five atom ic sites of this structure w ere found to be fully occupied w ithin the error lim its w ith the exception of one zinc site of TmNi2Zn20. The coordination for the site of the rare earth atom s is a Frank-K asper polyhedron with coordination num ber (CN) 16. The transition metal atom s occupy a site w ith icosahedral zinc coordination (CN 12). Two of the three zinc sites are in pentagonal prism atic coordination of zinc atom s, capped by rare earth and/or transition metal atom s (CN 12), w hile the third zinc site has 12 zinc neighbors form ing a hexagonal prism , w hich is capped by tw o rare earth atom s (CN 14).
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Reeves, Matthew G., Peter A. Wood i Simon Parsons. "Automated oxidation-state assignment for metal sites in coordination complexes in the Cambridge Structural Database". Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 75, nr 6 (14.11.2019): 1096–105. http://dx.doi.org/10.1107/s2052520619013040.
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The Cambridge Structural Database (CSD) currently contains over 400 000 transition-metal-containing entries, however many entries still lack curated oxidation-state assignments. Surveying and editing the remaining entries would be far too resource- and time-intensive to be carried out manually. Here, a highly reliable automated workflow for oxidation-state assignment in transition-metal coordination complexes via CSD Python API (application programming interface) scripts is presented. The strengths and limitations of the bond-valence sum (BVS) method are discussed and the use of complementary methods for improved assignment confidence is explored. In total, four complementary techniques have been implemented in this study. The resulting workflow overcomes the limitations of the BVS approach, widening the applicability of an automated procedure to more CSD entries. Assignments are successful for 99% of the cases where a high consensus between different methodologies is observed. Out of a total number of 54 999 unique metal atoms in a test dataset, the procedure yielded the correct oxidation state in 47 072 (86%) of cases.
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Sivo, Valeria, Gianluca D’Abrosca, Luigi Russo, Rosa Iacovino, Paolo Vincenzo Pedone, Roberto Fattorusso, Carla Isernia i Gaetano Malgieri. "Co(II) Coordination in Prokaryotic Zinc Finger Domains as Revealed by UV-Vis Spectroscopy". Bioinorganic Chemistry and Applications 2017 (2017): 1–7. http://dx.doi.org/10.1155/2017/1527247.
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Co(II) electronic configuration allows its use as a spectroscopic probe in UV-Vis experiments to characterize the metal coordination sphere that is an essential component of the functional structure of zinc-binding proteins and to evaluate the metal ion affinities of these proteins. Here, exploiting the capability of the prokaryotic zinc finger to use different combinations of residues to properly coordinate the structural metal ion, we provide the UV-Vis characterization of Co(II) addition to Ros87 and its mutant Ros87_C27D which bears an unusual CysAspHis2 coordination sphere. Zinc finger sites containing only one cysteine have been infrequently characterized. We show for the CysAspHis2 coordination an intense d-d transition band, blue-shifted with respect to the Cys2His2 sphere. These data complemented by NMR and CD data demonstrate that the tetrahedral geometry of the metal site is retained also in the case of a single-cysteine coordination sphere.
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Ding, Zhizhong, Yongchun Dong i Bing Li. "Preparation of a Modified PTFE Fibrous Photo-Fenton Catalyst and Its Optimization towards the Degradation of Organic Dye". International Journal of Photoenergy 2012 (2012): 1–8. http://dx.doi.org/10.1155/2012/121239.
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Polytetrafluoroethylene (PTFE) fiber was grafted with acrylic acid to impart the carboxyl groups onto the fiber surface, which were used to coordinate with both transition metal ions Fe(III) and Cu(II) and a rare metal ion Ce(III) to prepare the metal grafted PTFE fiber complexes as the novel heterogeneous Fenton catalysts for the degradation of the azo dye in water under visible irradiation. Some factors affecting the preparation process, such as nature and concentration of metal ions in the coordination solution, grafting degree of PTFE and reaction temperature were optimized with respect to the content and strength of metal fixation on the fiber and dye degradation efficiency. The results indicated that increasing metal ion concentrations in solution and grafting degree of PTFE fiber as well as higher coordination temperature led to a significant increase in metal content, especially Fe(III) and Cu(II) content of the complexes. Fe(III) ions fixed on the fiber showed the better catalytic performance than Cu(II) and Ce(III) ions fixed when three different complexes with similar metal content being employed, respectively. Moreover, Increasing Fe content or incorporation of Cu(II) ions could significantly improve the catalytic activity of the complexes.
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Deng, Huiyun, Handou Zheng, Heng Gao, Lixia Pei i Haiyang Gao. "Late Transition Metal Catalysts with Chelating Amines for Olefin Polymerization". Catalysts 12, nr 9 (24.08.2022): 936. http://dx.doi.org/10.3390/catal12090936.
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Polyolefins are the most consumed polymeric materials extensively used in our daily life and are usually generated by coordination polymerization in the polyolefin industry. Olefin polymerization catalysts containing transition metal–organic compound combinations are undoubtedly crucial for the development of the polyolefin industry. The nitrogen donor atom has attracted considerable interest and is widely used in combination with the transition metal for the fine-tuning of the chemical environment around the metal center. In addition to widely reported olefin polymerization catalysts with imine and amide donors (sp2 hybrid N), late transition metal catalysts with chelating amine donors (sp3 hybrid N) for olefin polymerization have never been reviewed. In this review paper, we focus on late transition metal (Ni, Pd, Fe, and Co) catalysts with chelating amines for olefin polymerization. A variety of late transition metal catalysts bearing different neutral amine donors are surveyed for olefin polymerization, including amine–imine, amine–pyridine, α-diamine, and [N, N, N] tridentate ligands with amine donors. The relationship between catalyst structure and catalytic performance is also encompassed. This review aims to promote the design of late transition metal catalysts with unique chelating amine donors for the development of high-performance polyolefin materials.
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Hayward, Michael A. "Synthesis and Magnetism of Extended Solids Containing Transition-Metal Cations in Square-Planar, MO4 Coordination Sites". Inorganic Chemistry 58, nr 18 (28.05.2019): 11961–70. http://dx.doi.org/10.1021/acs.inorgchem.9b00960.
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Wang, Yuehua, Shuang Li, Rui Xu, Junpeng Chen, Yifan Hao, Ke Li, Yan Li, Yingmei Li i Jing Wang. "Dual Metal Site Fe Single Atom Catalyst with Improved Stability in Acidic Conditions". Catalysts 13, nr 2 (16.02.2023): 418. http://dx.doi.org/10.3390/catal13020418.
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Dual atom catalysts (DACs) not only retain uniform active sites and high atomic utilization efficiency as the single atom catalysts, but the two adjacent metal sites also cooperate and play a synergistic role to achieve additional benefits. However, the relationships connecting their dual-site synergistic effects on catalytic performance are not well rationalized due to limited pairs available from experiments. Herein, Fe/M dual sites supported by nitrogen doped carbon (Fe/M-N-C whereby M from 3 d–5 d electron containing transition metals) have been screened as an oxygen reduction reaction (ORR) catalyst. The results show that the absorption strength of ORR intermediates on four nitrogen coordinated metals is weaker than the three coordinated metals, which promotes favourable ORR activities. As a result, we recommended FeIr, FeRh, FeRu and FeOs as promising ORR catalysts. Ab initio molecular dynamic (AIMD) simulations suggest Fe/M-N-C (M = Ir, Rh, Ru and Os) catalysts with encouraging structural stability at room temperature. Furthermore, it is found that the nitrogen atoms in-between metals are vulnerable sites for proton attacking, yet the protonation process demands high energy, even under O2 atmosphere, which underlines good tolerance under acidic conditions. This work provides a broad understanding of Fe based catalyst and a new direction for catalytic design.
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Biggs, George S., Oskar James Klein, Sally R. Boss i Paul D. Barker. "Unlocking the Full Evolutionary Potential of Artificial Metalloenzymes Through Direct Metal-Protein Coordination : A review of recent advances for catalyst development". Johnson Matthey Technology Review 64, nr 4 (1.10.2020): 407–18. http://dx.doi.org/10.1595/205651320x15928204097766.
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Generation of artificial metalloenzymes (ArMs) has gained much inspiration from the general understanding of natural metalloenzymes. Over the last decade, a multitude of methods generating transition metal-protein hybrids have been developed and many of these new-to-nature constructs catalyse reactions previously reserved for the realm of synthetic chemistry. This perspective will focus on ArMs incorporating 4d and 5d transition metals. It aims to summarise the significant advances made to date and asks whether there are chemical strategies, used in nature to optimise metal catalysts, that have yet to be fully recognised in the synthetic enzyme world, particularly whether artificial enzymes produced to date fully take advantage of the structural and energetic context provided by the protein. Further, the argument is put forward that, based on precedence, in the majority of naturally evolved metalloenzymes the direct coordination bonding between the metal and the protein scaffold is integral to catalysis. Therefore, the protein can attenuate metal activity by positioning ligand atoms in the form of amino acids, as well as making non-covalent contributions to catalysis, through intermolecular interactions that pre-organise substrates and stabilise transition states. This highlights the often neglected but crucial element of natural systems that is the energetic contribution towards activating metal centres through protein fold energy. Finally, general principles needed for a different approach to the formation of ArMs are set out, utilising direct coordination inspired by the activation of an organometallic cofactor upon protein binding. This methodology, observed in nature, delivers true interdependence between metal and protein. When combined with the ability to efficiently evolve enzymes, new problems in catalysis could be addressed in a faster and more specific manner than with simpler small molecule catalysts.