Academic literature on the topic 'Carbène NHC'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Carbène NHC.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Carbène NHC":
1
Alauddin, Mohammad, and Mazharul M. Islam. "A computational characterization of N-heterocyclic carbenes for catalytic and nonlinear optical applications." Zeitschrift für Naturforschung B 79, no. 4 (April 1, 2024): 215–23. http://dx.doi.org/10.1515/znb-2023-0092.
Abstract:
Abstract Very recently, N-heterocyclic carbenes (NHCs) have found a wide range of applications in the fields of catalysis and nonlinear optics. Herein, we have employed 1,3-bis-(1(S)-benzyl)-4,5-dihydro-imidazol-based carbene as a reference molecule and substituted one H atom from each CH2 of the benzyl groups in both sides by CH3, NH2, and CF3 to study the thermodynamic and opto-electronic properties of NHCs theoretically. It was observed that the enthalpy (H), Gibb’s free energy (G), specific heat capacity (C v), and entropy (S) increase significantly in the presence of the electron-withdrawing groups compared to the electron-donating groups. The IR active in-plane bending vibrations of the CH (NHC) group are shifted to the higher frequency region for the considered substituted molecules compared to the reference carbene. The analysis of the electronic properties shows that the CH3-substituted carbene is more reactive for catalytic activities compared to other NHCs. The calculated nonlinear optical (NLO) properties reveal that the NH2-substituted NHC has the largest hyperpolarizability value whereas the CH3-substituted NHC has the largest dipole moment and polarizability among all, making them potential candidates for the development of NLO materials.
2
Mokfi, Moloud, Jörg Rust, Christian W. Lehmann, and Fabian Mohr. "Facile N9-Alkylation of Xanthine Derivatives and Their Use as Precursors for N-Heterocyclic Carbene Complexes." Molecules 26, no. 12 (June 17, 2021): 3705. http://dx.doi.org/10.3390/molecules26123705.
Abstract:
The xanthine-derivatives 1,3,7-trimethylxanthine, 1,3-dimethyl-7-benzylxanthine and 1,3-dimethyl-7-(4-chlorobenzyl)xanthine are readily ethylated at N9 using the cheap alkylating agents ethyl tosylate or diethyl sulfate. The resulting xanthinium tosylate or ethyl sulfate salts can be converted into the corresponding PF6- and chloride salts. The reaction of these xanthinium salts with silver(I) oxide results in the formation of different silver(I) carbene-complexes. In the presence of ammonia, ammine complexes [Ag(NHC)(NH3)]PF6 are formed, whilst with Et2NH, the bis(carbene) salts [Ag(NHC)2]PF6 were isolated. Using the xanthinium chloride salts neutral silver(I) carbenes [Ag(NHC)Cl] were prepared. These silver complexes were used in a variety of transmetallation reactions to give the corresponding gold(I), ruthenium(II) as well as rhodium(I) and rhodium(III) complexes. The compounds were characterized by various spectroscopic methods as well as X-ray diffraction.
3
Longevial, Jean-François, Mamadou Lo, Aurélien Lebrun, Danielle Laurencin, Sébastien Clément, and Sébastien Richeter. "Molecular complexes and main-chain organometallic polymers based on Janus bis(carbenes) fused to metalloporphyrins." Dalton Transactions 49, no. 21 (2020): 7005–14. http://dx.doi.org/10.1039/d0dt00594k.
Abstract:
Janus bis(N-heterocyclic carbenes) composed of a porphyrin core with two N-heterocyclic carbene (NHC) heads fused to opposite pyrroles were used as bridging ligands for the preparation of metal complexes.
4
Jutand, Anny, Julien Pytkowicz, Sylvain Roland, and Pierre Mangeney. "Mechanism of the oxidative addition of aryl halides to bis-carbene palladium(0) complexes." Pure and Applied Chemistry 82, no. 7 (May 4, 2010): 1393–402. http://dx.doi.org/10.1351/pac-con-09-09-22.
Abstract:
Bis-N-heterocyclic carbenes Pd0 complexes, Pd0(NHC)2, are efficient catalysts in Heck reactions performed with aryl bromides or chlorides. The Pd0(NHC)2 that are not stable are generated in situ from PdII precursors PdY2(NHC)2 (Y = halides) after a chemical reduction. The latter procedure can be mimicked by an electrochemical reduction. The transient Pd0(NHCBn)2 is generated by electrochemical reduction of PdY2(NHCBn)2, and its reactivity in oxidative addition to aryl bromides and chlorides is characterized by the same electrochemical technique with the determination of the rate constants. Pd0(NHCBn)2 is found to be more reactive than the mixed complex Pd0(NHCBn)(PPh3). Both are the reactive species in an associative mechanism. Comparison with the isolated Pd0(NHCtBu)2 reveals that Pd0(NHCBn)2 is more reactive than Pd0(NHCtBu)2 even if the latter reacts via the mono-carbene Pd0(NHCtBu) in a dissociative mechanism. This suggests that the formation of mono-carbene Pd0(NHC) is not a guarantee for a fast oxidative addition because it is always generated at low concentration in its equilibrium with the related nonreactive bis-carbene Pd0(NHC)2.
5
Nonnenmacher, Michael, Dominik M. Buck, and Doris Kunz. "Experimental and theoretical investigations on the high-electron donor character of pyrido-annelated N-heterocyclic carbenes." Beilstein Journal of Organic Chemistry 12 (August 23, 2016): 1884–96. http://dx.doi.org/10.3762/bjoc.12.178.
Abstract:
Rh(CO)2Cl(NHC) complexes of dipyrido-annelated N-heterocyclic carbenes were prepared. From the C–H coupling constant of the respective imidazolium salts and the N–C–N angle of the N-heterocyclic carbene (NHC), a weaker σ-donor character than that of typical unsaturated NHCs is expected. However, the IR stretching frequencies of their Rh(CO)2Cl complexes suggest an electron-donor character even stronger than that of saturated NHCs. We ascribe this to the extremely weak π-acceptor character of the dipyrido-annelated NHCs caused by the conjugated 14 πe− system that thus allows for an enhanced Rh–CO backbonding. This extremely low π-acceptor ability is also corroborated by the 77Se NMR chemical shift of −55.8 ppm for the respective selenourea, the lowest value ever measured for imidazole derived selenoureas. DFT-calculations of the free carbene confirm the low σ-donor character by the fact that the σ-orbital of the carbene is the HOMO−1 that lies 0.58 eV below the HOMO which is located at the π-system. Natural population analysis reveals the lowest occupation of the pπ-orbital for the saturated carbene carbon atom and the highest for the pyrido-annelated carbene. Going from the free carbene to the Rh(CO)2Cl(NHC) complexes, the increase in occupancy of the complete π-system of the carbene ligand upon coordination is lowest for the pyrido-annelated carbene and highest for the saturated carbene.
6
Qie, Boyu, Ziyi Wang, Jingwei Jiang, Zisheng Zhang, Peter H. Jacobse, Jiaming Lu, Xinheng Li, et al. "Synthesis and characterization of low-dimensional N-heterocyclic carbene lattices." Science 384, no. 6698 (May 24, 2024): 895–901. http://dx.doi.org/10.1126/science.adm9814.
Abstract:
The covalent interaction of N-heterocyclic carbenes (NHCs) with transition metal atoms gives rise to distinctive frontier molecular orbitals (FMOs). These emergent electronic states have spurred the widespread adoption of NHC ligands in chemical catalysis and functional materials. Although formation of carbene-metal complexes in self-assembled monolayers on surfaces has been explored, design and electronic structure characterization of extended low-dimensional NHC-metal lattices remains elusive. Here we demonstrate a modular approach to engineering one-dimensional (1D) metal-organic chains and two-dimensional (2D) Kagome lattices using the FMOs of NHC–Au–NHC junctions to create low-dimensional molecular networks exhibiting intrinsic metallicity. Scanning tunneling spectroscopy and first-principles density functional theory reveal the contribution of C–Au–C π-bonding states to dispersive bands that imbue 1D- and 2D-NHC lattices with exceptionally small work functions.
7
Rey, Yannick P., and Ryan Gilmour. "Modulating NHC catalysis with fluorine." Beilstein Journal of Organic Chemistry 9 (December 6, 2013): 2812–20. http://dx.doi.org/10.3762/bjoc.9.316.
Abstract:
Fluorination often confers a range of advantages in modulating the conformation and reactivity of small molecule organocatalysts. By strategically introducing fluorine substituents, as part of a β-fluoroamine motif, in a triazolium pre-catalyst, it was possible to modulate the behaviour of the corresponding N-heterocyclic carbene (NHC) with minimal steric alterations to the catalyst core. In this study, the effect of hydrogen to fluorine substitution was evaluated as part of a molecular editing study. X-ray crystallographic analyses of a number of derivatives are presented and the conformations are discussed. Upon deprotonation, the fluorinated triazolium salts generate catalytically active N-heterocyclic carbenes, which can then participate in the enantioselective Steglich rearrangement of oxazolyl carbonates to C-carboxyazlactones (e.r. up to 87.0:13.0).
8
Ojha, Minita, Shweta Choudhary, and Raj K. Bansal. "3-Benzylbenzothiazolylidene Carbene Catalyzed Isomerization of Dimethyl Maleate to Dimethyl Fumarate: Experimental and Theoretical Results." Current Organocatalysis 7, no. 2 (July 2, 2020): 108–17. http://dx.doi.org/10.2174/2213337206666191018111354.
Abstract:
Background: N-Heterocyclic Carbenes (NHCs) have emerged as ubiquitous species having applications in a broad range of fields, including organocatalysis and organometallic chemistry. Since Arduengo and co-workers first isolated a bottlable NHC, namely imidazol-2-ylidene derivative, these nucleophilic species have attained a prominent place in synthetic organic chemistry. The NHC-induced non-asymmetric catalysis has turned out to be a really fruitful area of research in recent years. Methods and Results: The quantitative aspects of the experimental and theoretical investigation of isomerization of dimethyl maleate to dimethyl fumarate catalyzed by an N-heterocyclic carbene (NHC), namely 3-benzylbenzothiazolylidene are being reported for the first time. Dimethyl maleate on treating with 3-benzylbenzothiazolylidene carbene (10 mol%), generated in situ from the reaction of 3- benzylbenzothiazolium bromide with triethylamine in diethyl ether at room temperature under nitrogen atmosphere isomerizes quantitatively to dimethyl fumarate. Theoretical investigation of a model reaction scheme at the wB97XD/6-31+G(d) level reveals that initial attack of the carbene, which is the ratedetermining step, is followed by rotation about the C-C bond in preference to a higher activation free energy path involving proton abstraction. The species so formed splits off the carbene to yield dimethyl fumarate. Eyring equation has been used to rationalize the effect of temperature on the isomerization rate. Conclusions and Perspective: 3-Benzylbenzothiazolylidene carbene catalyzes the isomerization of dimethyl maleate to its trans-isomer. This carbene can be used in other catalytic reactions, such as acyloin condensation and Stetter reaction.
9
Zhu, Tingshun, Ke Xu, and Ziyuan Wang. "N-Heterocyclic Carbene-Organocatalyzed Arene Formation: Application in Atroposelective Synthesis of Polysubstituted Benzenes." Synlett 31, no. 10 (February 3, 2020): 925–32. http://dx.doi.org/10.1055/s-0039-1690814.
Abstract:
In recent decades, organocatalysis by N-heterocyclic carbenes (NHCs) has emerged as a versatile and powerful method in organic synthesis. As a result of the power of NHC organocatalysis to produce cyclic compounds, polysubstituted benzenes, which are among the most important cyclic compounds in organic chemistry, can be synthesized efficiently and selectively. This article briefly summarizes the history of NHC organocatalysis, including recent developments in benzene-formation methods, and highlights our recent work in atroposelective arene formation by carbene-catalyzed formal [4+2] cycloadditions. We expect that more NHC-catalyzed methods for the synthesis of asymmetric arenes will be developed in the near future, providing shortcuts to syntheses of sophisticated chiral functional molecules with polysubstituted benzene nuclei.
10
Tang, Xiang-Ting, Fan Yang, Ting-Ting Zhang, Yi-Fan Liu, Si-Yu Liu, Tong-Fu Su, Dong-Can Lv, and Wen-Bo Shen. "Recent Progress in N-Heterocyclic Carbene Gold-Catalyzed Reactions of Alkynes Involving Oxidation/Amination/Cycloaddition." Catalysts 10, no. 3 (March 20, 2020): 350. http://dx.doi.org/10.3390/catal10030350.
Abstract:
Recent rapid development in homogeneous gold catalysis affords an alternative and particularly thriving strategy for the generation of gold carbenes through gold-catalyzed oxidation/amination/cycloaddition of alkynes, while it avoids the employment of hazardous and potentially explosive diazo compounds as starting materials for carbene generation. In addition to facile and secure operation, gold carbenes generated in this strategy display good chemoselectivity distinct from other metal carbenes produced from the related diazo approach. N-heterocyclic carbene (NHC) gold is a special metal complex that can be used as ancillary ligands, which provides enhanced stability and can also act as an efficient chiral directing group. In this review, we will present an overview of these recent advances in alkyne oxidation/amination/cycloaddition by highlighting their specificity and applicability, aiming to facilitate progress in this very exciting area of research.
Dissertations / Theses on the topic "Carbène NHC":
1
Haumesser, Julien. "Synthèse et caractérisation d'assemblages multi-porphyriniques à espaceurs NHC." Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-01017421.
Abstract:
L'objectif de cette thèse a été de mettre au point l'introduction d'azoles en meso d'une porphyrine par couplage d'Ullmann; Divers azoles ont pu être introduit par cette méthode avec de bons rendements, par formation d'une liaison carbone-azote. il a même été possible avec certains azotes de réaliser des doubles couplages d'Ullmann, conduisant ainsi à des 5.15-diazolyle-porphyrines. De plus, ces même conditions réactionnelles ont été utilisées pour introduire un ou deux dérivés donneurs d'électrons (carbazole, phénoxazine, phénothiazine). L'introduction d'imidazole, de triazole et de benzimidazole en meso a permis, après alkylation, d'obtenir des précurseurs de carbènes N-hétérocycles (NHC). La coordination de deux équivalents de NHC sur un sel de palladium conduit à un dimère de porphyrines via coordination exocyclique. La géométrie de coordination trans-anti autour du palladium a été confirmée par l'obtention de la structure radiocristallographique de deux complexes. Les études par électrochimie de ces complexes ont révélé une communication interporphyrinique à l'état fondamental, mise en évidence par une succession de quatre vagues monoélectroniques en oxydation.
2
Kong, Lingyu. "De ligands NHCs prochiraux à des complexes métal-NHC énantiopurs : nouvelles perspectives pour la catalyse asymétrique." Electronic Thesis or Diss., Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0502.
Abstract:
Les carbènes N-hétérocycliques (NHC) sont connus pour être de bons ligands des métaux de transition (TM). Dans ce manuscrit, le premier chapitre est consacré une présentation non exhaustive des différentes approches qui ont été utilisées dans la littérature pour le design de NHCs chiraux efficaces en catalyse enantiosélective. Au début du deuxième chapitre, le nouveau concept est présenté. Celui-ci repose sur la formation d’un axe de chiralité qui est créé lors de la coordination du ligand NHC à un métal de transition. Ce chapitre est consacré à la synthèse de complexes possédant une symétrie C1. Différents sels d’imidazolium, précurseurs des NHCs, ont été synthétisés et utilisé pour former des complexes palladium. Ils ont été sous forme énantiopure par HPLC chirale à l’échelle préparative. Ces complexes ont fait l’objet d’études concernant leurs propriétés chiroptiques et leurs barrières de rotation avant d’être testé en catalyse. Le concept a été ensuite étendu pour la synthèse de complexes d’or et de cuivre. Ces derniers se sont avérés être intéressants car non seulement ils ont permis d’obtenir de bons excès énantiomériques en catalyse mais leurs utilisations comme agent de transfert de ligands NHC a permis de proposer un mécanisme pour le procédé de transmétallation. Le troisième chapitre fait état des travaux qui ont été réalisés sur la préparation de complexes chiraux NHC-TM possédant une symétrie C2. Différents sels d’imidazolium symétriques ont été synthétisés et utilisés pour former des complexes de palladium. Les versions homochirales de ces complexes se sont avérées être d’excellents catalyseurs chiraux pour la réaction l’α-arylation d’amides (jusqu’à 98% ee)N-heterocyclic carbenes (NHC) are recognized to be excellent ligands towards transition metals ™. In this manuscript, the first chapter is dedicated to a non-exhaustive presentation of the various approaches of the literature which have been used to design chiral NHCs efficient in enantioselective catalysis. As a prelude of the second chapter, the new concept lies on the formation of an axis of chirality during the coordination between the NHC ligand and the transition metal. This chapter is dedicated to the synthesis of complexes with a C1 symmetry. Various imidazolium salts, have been synthesized and then used to generate palladium complexes. These complexes have been obtained in a enantiopurically form thanks to a chiral HLPC resolution at a preparative scale. These homochiral complexes were firstly subjected to studies aiming the investigation of their chiroptic properties and the determination of their rotation barriers values. The concept was then successfully extended to the synthesis of gold- and copper-based complexes. Homochiral copper-NHC complexes were found of particular importance since their applications in catalysis allowed to reach good enantioinductions and as NHC transfer reagents brought some experimental proofs on the transmetalation process. The third chapter disclosed the works that have been done on the preparation of heterochiral NHC-TM complexes possessing a C2 symmetry. Various symmetric imidazolium salts have been synthesized and then used to form the corresponding palladium-based complexes. Homochiral complexes were found displaying good activities for α-arylation of amides and excellent enantioselectivities (up to 98% ee)
3
Passays, Johan. "Nouveaux ligands mixtes de type phosphore / carbène N-hétérocyclique : synthèse et applications en catalyse asymétrique." Thesis, Rouen, INSA, 2011. http://www.theses.fr/2011ISAM0008.
Abstract:
Une méthode simple et efficace a été développée pour la préparation de ligands bifonctionnels associant les motifs phosphine ou phosphite d'une part, et carbène Nhétérocyclique(NHC) ou imidazolium d'autre part. Dans un premier temps, une série de ligands diphénylphosphine-carbène chiraux portant un centre stéréogène en a de la phosphinea été développée à partir b-hydroxyesters. Une famille de ligands a ainsi été développée afin d'évaluer l'influence de l'encombrement stérique de différents groupements alkyles en a de la phosphine et de la nature des groupements aromatiques portés sur l'imidazole sur leur activité catalytique. L’étude s’est ensuite étendue à la synthèse de ligands de type dialkylphosphine carbène et phosphite-carbène. Ces différents ligands ont été complexés avec des métaux tels que l’iridium ou le rhodium de manière à en étudier l’activité en hydrogénation asymétriqueA straightforward method for the preparation of new bidentate ligands containing aphosphine or a phosphite and a carbene function was developed. Different phosphorus-imidazolium compounds were prepared according to this method. First, diphenylphosphine-NHC ligands featuring a stereogenic center a to the phosphine were synthesized from b-hydroxyesters. This strategy was then extended to the preparation of phosphite-imidazoliumand dialkylphosphine-imidazolium compounds. Complexation of these phosphorus-NHCligands with different metals like Ir or Rh was performed in order to study there catalytic properties in asymmetric hydrogenation
4
Tang, Shun. "Cycloisomérisations catalysées par les sels du gallium et les complexes NHC-Gallium(III)." Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112271.
Abstract:
Afin de développer des méthodes alternatives à l'activation de systèmes Pi en catalyse homogène par des métaux nobles coûteux et toxiques, nous nous sommes focalisés sur des complexes métalliques et plus particulièrement ceux de la colonne du group XIII. Cette thèse approche une contribution à ce champ d'études, et nous nous sommes particulièrement concentrés sur la chimie de gallium.Trois principaux aspects ont été étudiés dans ce manuscrit: la réactivité des halogénures de gallium(III), des complexes bien définis de gallium (III) portant carbènes N- hétérocycliques (NHCs), et leur activation de systèmes en catalyse.La thèse est divisée en trois chapitres. Le premier chapitre donne un aperçu des travaux effectués dans le domaine de la synthèse organique faisant intervenir des composés de gallium (III) , en se concentrant sur leur utilisation en tant qu’ acides de Lewis et .Dans le deuxième chapitre, nous avons tenté d'exploiter le potentiel catalytique de GaCl3 dans une nouvelle réaction de cycloisomérisation/Friedel-Crafts en tandem. Une section dédiée à l'étude sur l’hydratation d’alcyne catalysée par GaCl3 est également fournie.Le troisième chapitre commence par une description de la synthèse d'une série de complexes de gallium (III) portant diverses NHCs comme ligands pour surmonter les limites des halogénures de gallium(III) en catalyse. Ensuite, des études de méthodologie sur le processus de tandem impliquant arenynes-1,6 avec les gallium(III) complexes neutres et cationiques ont été décrits. Une évaluation cinétique pour des catalyseurs, des divers substrats et l'influence de contreanions sont discutés. En outre, les efforts dans la version asymétrique de cette tandem transformation et des autres cyclisations sont également présentés.Le dernier chapitre reprend les résultats les plus importants obtenus dans la thèse. Et les orientations futures de la recherche sur l'utilisation des complexes NHC- gallium (III) sont discutéesRecently, in order to develop alternative activation methods for Pi-systems in homogeneous catalysis instead of employing expensive and toxic noble metal catalysts, first row transition metals and main group metal complexes have attracted great attention. This thesis is a contribution to it, and we focus on gallium chemistry. There are three main aspects dominating this thesis: gallium(III) halides, well-defined gallium(III) complexes bearing N-heterocyclic carbenes (NHCs), and -systems activation in catalysis.The thesis is divided into three chapters. Chapter I provides an overview of the field of organic synthesis involving gallium(III) compounds, focusing on their use as - or -Lewis acids.In Chapter II, we expose our attempts to exploit the catalytic potential of gallium(III) chloride in a novel tandem cycloisomerization/Friedel-Crafts reaction. A section dedicated to the study on GaCl3-catalyzed alkyne hydration is also provided.Chapter III begins with a description of the synthesis of a series of gallium(III) complexes bearing various NHCs as ligands in order to overcome the limitations of gallium(III) halides in catalysis. Next, methodology studies on the tandem process involving 1,6-arenynes with the neutral and cationic gallium(III) complexes are described. The evaluation of scission kinetics for catalysts, substrates variation and influence of counteranions are discussed. In addition, efforts towards the asymmetric version of this tandem transformation and some other cyclizations are also presented.The concluding chapter reiterates the most important results obtained in the body chapters of the thesis. To conclude, the future directions for the research on the use of the NHC-gallium(III) complexes are discussed
5
Gojon, Sophie. "Carbènes N-hétérocycliques : nouvelle méthode de synthèse et activité catalytique pour la réticulation de silicone." Toulouse 3, 2011. http://www.theses.fr/2011TOU30321.
Abstract:
Ce travail concerne l'étude de carbènes de type N-hétérocyclique (NHCs) sous deux aspects : synthèse et réactivitéThe main objective of this thesis is to study the synthesis of N-heterocyclic (NHCs) and their catalytic activity toward silicone elastomer formation
6
Darari, Mohamed. "Synthèse et caractérisation de nouveaux complexes Fe-NHC applicables en cellule solaire DSSC." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0318.
Abstract:
Ces travaux de thèse se situent dans un domaine au cœur des préoccupations actuelles qui est le développement de nouveaux complexes photoactifs utilisant des métaux abondants pour remplacer les métaux nobles dans les dispositifs à énergie renouvelable. De nouvelles familles de complexes précurseurs ou sensibilisateurs potentiels pour les cellules DSSC (Dye-sensitized solar cells) à base de fer et de ligands tridentates pyridyl-carbènes (FeNHC) ont été préparées et caractérisées. L’objectif, à côté de l’aspect applicatif pour l’énergie, est d’accroître les connaissances dans l’étude des relations structure-propriétés dans les complexes homoleptiques Fe-NHC portant des ligands pyridyl-bisimidazolylidènes par modification du noyau central, du groupe de greffage et de la géométrie de coordination. Après mise au point de la synthèse, les complexes ont fait l’objet de différentes caractérisations photophysiques, électrochimiques et théoriques. Un nouveau record de durée de vie des états excités MLCT a été obtenu avec des complexes à noyau pyrazine (32 ps). L’optimisation géométrique, c’est-à-dire le design de ligands permettant d’obtenir une géométrie de coordination octaédrique idéale pour induire un champ de ligand fort a été étudiée. Nous avons obtenu les complexes recherchés (structure attestée par diffraction RX) en accroissant la distance entre le cœur pyridine et les carbènes latéraux. Cette modification induit un décalage bathochrome, mais la conjugaison électronique ainsi que la rigidité du complexe restent à optimiser. Nous avons aussi développé une nouvelle voie de synthèse permettant d’introduire des groupes d’accroche Π-étendus dans le but de limiter la recombinaison de charge après injection dans le semi-conducteur TiO2. Enfin, Le rendement des cellules DSSC a été optimisé par l’incorporation d’un nouvel additif MgI2 dans la composition de l’électrolyte permettant d’atteindre une efficacité de 0.5% inédite pour un complexe de fer. Au final ces travaux de thèse mettent à la disposition de la communauté des outils synthétiques pour la conception de complexes FeII-NHC à durée de vie prolongée à l'état excité, et représentent une étape supplémentaire dans la compréhension des processus photophysiques opérés au sein de ces complexesThis thesis is part of a current concern and high interest research field, which is the development of new photoactive complexes using abundant metals to replace noble metals in renewable energy devices. Novel families of potential sensitizers for DSSC (Dye-sensitized solar cells) based on iron and tridentate pyridyl-carbene ligands (FeNHC) have been prepared and characterized. The aim, besides the application aspect for energy, is to increase the understanding of the structure-property relationships in Fe-NHC homoleptic complexes carrying pyridyl-bisimidazolylidene ligands by modification of the central core, anchoring group and coordination geometry. Once synthesized, the complexes were submitted to various photophysical, electrochemical and theoretical characterizations. A new MLCT excited state lifetime record was obtained with a pyrazine-based complexes (32 ps). The geometric optimization, which means the design of ligands to obtain an ideal octahedral coordination geometry to induce a strong ligand field was studied. X-ray diffraction measurements attested that the desired complexes were obtained by increasing the distance between the pyridine core and the lateral carbenes. This modification induces a bathochromic shift, but the electronic conjugation as well as the rigidity of the complexes remain to be optimized further. We have also developed a novel synthetic route for introducing Π-extended anchoring groups in order to limit the charge recombination after the injection into the TiO2 semiconductor. The efficiency of the DSSC cells was optimized by the incorporation of a new MgI2 additive in the electrolyte composition which led to an unprecedented efficiency of 0.5% for an iron complex. Finally, this thesis offers new synthetic tools for the design of FeII-NHC complexes with extended excited state lifetimes and represents a further step in the understanding of the photophysical processes operated within this type of iron complexes
7
Savchuk, Mariia. "Complexes atropisomériques d'or-NHC : design, synthèse et applications dans des réactions de cycloisomérisation asymétriques." Electronic Thesis or Diss., Aix-Marseille, 2022. http://www.theses.fr/2022AIXM0571.
Abstract:
Le premier chapitre de ce manuscrit est consacré à l’étude des différents designs de NHCs chiraux décrits dans la littérature et leurs applications en tant que ligand dans les transformations énantiosélectives catalysées par l’or. Un nouveau concept de complexes atroipsomériques métal de transition-NHC a été conçu et développé dans notre groupe. Son application pour préparer des complexes de métaux de transition chiraux portant un ligand NHC de symétrie C1 contenant un NHC saturé a été étudiée au cours de mes travaux de doctorat et sera présentée dans le deuxième chapitre. Divers complexes chiraux ont été obtenus, séparés par HPLC chirale à l’échelle préparative et leurs stabilités configurationnelles ont été étudiées en profondeur. Le complexe contenant de l’or(I) a été testé pour la cycloisomérisation d’1,6-énynes, donnant une énantiosélectivité prometteuse (70% ee). Dans le troisième chapitre de ce manuscrit, le concept de complexes atroipsomériques métal de transition-NHC a été étendu à des ligands NHCs de symétrie C2 et appliqué des transformations asymétriques catalysées par de l’or(I). Les 1,6-énynes possédant un lien malonate de diisopropyle se sont avérés être d’excellents substrats pour des réactions de cycloisomérisation et les produits d’alcoxycyclisation qui en ont résultées ont été isolés avec d’excellentes énantiopuretés (7 exemples avec des rendements de 51 à 92% et des excès énantiomériques compris entre 56 et 99%). La cycloisomérisation lorsqu’elle est réalisée sans nucléophile externe a également conduit à d’excellents résultats (6 exemples avec des rendements allant de 72 à 99%, et des excès énantiomériques dans la gamme 86-93% ee)The first chapter of this manuscript is dedicated to survey the design of chiral NHC and their applications as ligand in gold-catalyzed enantioselective transformations. This presentation clearly showed the importance of new ligand designs, because only poor enantioselectivities have been reached up to date. A new concept of atroipsomeric transition metal-NHC complexes has been devised and developed in our group. Its application to prepare chiral transition metal complexes bearing C1-symmetric NHC ligand containing a satured backbone was investigated during my Ph.D. work and will be presented in the second chapter. Various chiral complexes were obtained, separated by chiral HPLC at preparative scale and their configurational stabilities were investigated in depth. The gold (I) containing complex was tried in the 1,6-enyne cycloisomerization, giving a promissing enantioselectivity (70% ee). In the third chapter of this manuscript, the concept of atroipsomeric transition metal-NHC complexes was extended to C2-symmetric NHC ligands and applied to the asymmetric Au(I)-catalyzed transformations. Diisopropyl malonate-tethered 1,6-enynes were identified as excellent substrates for cycloisomerization reactions and resulting alkoxycyclization products were isolated with excellent enantiopurities (7 examples with 51-92% yield, 56-99% ee). The cyclization without external nucleophiles led also to excellent results a (6 examples with 72-99% yield, 86-93% ee)
8
Hussein, Hiba. "Synthèses de nouveaux ligands carbènes à structures N-hétérocycliques et macro-N-Bis-hétérocycliques symétriques et dissymétriques. Études de leurs propriétés photophysiques, biologiques et de coordination." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0014.
Abstract:
L'objectif de ce travail de thèse consiste à préparer de nouvelles molécules photosensibles de type carbènes N-hétérocycliques, ligands ou complexes, dessinées pour répondre aux critères des photosensibilisateurs (PS) (molécules pures, hydrosolubles, biocompatibles, non toxiques, d'efficacité d'absorbance maximale, possédant de bonnes propriétés photophysiques) applicables dans le domaine des matériaux ou/et dans le domaine biomédical tel qu'en photothérapie. L'ambition étant d'optimiser les propriétés spectroscopiques des photosensibilisateurs et d'obtenir une bonne photoactivité. Ce travail de thèse décrit dans un premier chapitre un état de l'art non exhaustif concernant les macrocycles hétérocycliques, les carbènes N-hétérocycliques (NHC) et les macrocycles de type NHC ainsi qu'un rappel des propriétés attendues des molécules photosensibles. Dans un deuxième chapitre, il détaille les synthèses de ligands originaux N-hétérocycliques et N-bis-hétérocycliques bis-imidazolium de structures ouvertes ou macrocycliques fermées ainsi que leurs caractérisations physico-chimiques (infrarouge, RMN, spectroscopie de masse). Des structures cristallographiques de certains de ces macrocycles ont été obtenues par diffraction des rayons X. Dans un troisième et dernier chapitre, sont détaillés les différents essais de formation des carbènes et l'étude de leurs propriétés de complexation vis-à-vis des métaux de transition. Des calculs théoriques Gaussian viennent en appui de celle-ci. Une étude par fluorescence et par production d'oxygène singulet ainsi qu'une évaluation des propriétés biologiques des macrocycles et ligands flexibles présentés précédemment, montrent des propriétés photophysiques et biologiques prometteuses. De plus, une étude préliminaire intéressante de l'échange proton/deutérium des protons carbèniques des macrocycles bis-imidazolium est décriteThe objective of this thesis is to prepare new photosensitive molecules of N-heterocyclic carbenes, ligands or complexes, designed to meet the criteria of photosensitizers (PS) (pure, water-soluble, biocompatible, non-toxic molecules, with maximum absorbance efficiency, possessing good photophysical properties) applicable in the field of materials and/or in the biomedical field such as phototherapy. The ambition is to optimise the spectroscopic properties of the photosensitisers and to obtain a good photoactivity. This thesis describes in a first chapter a non-exhaustive state of the art concerning heterocyclic macrocycles, N-heterocyclic carbenes (NHC) and NHC macrocycles as well as a reminder of the expected properties of photosensitive molecules. In a second chapter, it details the syntheses of original N-heterocyclic and N-bis-heterocyclic bis-imidazolium ligands of open or closed macrocyclic structures as well as their physicochemical characterizations (infrared, NMR, mass spectroscopy). Crystallographic structures of some of these macrocycles were obtained by X-ray diffraction. In a third and final chapter, the various tests for the formation of carbenes and the study of their complexation properties towards transition metals are detailed. Theoretical Gaussian calculations are used to support this study. A fluorescence and singlet oxygen production study as well as an evaluation of the biological properties of the previously presented flexible macrocycles and ligands show promising photophysical and biological properties. In addition, an interesting preliminary study of the proton/deuterium exchange of carbon protons of bis-imidazolium macrocycles is described.Keywords: NHC, macrocyclic ligands, bipyridine, bithiazole, imidazolium, photosensitiser, photoactivity, anti-bacterial properties
9
Schnee, Gilles. "Synthèse et réactivité de nouveaux complexes des métaux du groupe 13 portés par des ligands carbènes N-hétérocycliques." Thesis, Strasbourg, 2012. http://www.theses.fr/2012STRAF053/document.
Abstract:
Au début de ces travaux, peu d’études avaient été faites sur la complexation des carbènes N-hétérocycliques avec des métaux oxophiles, électropositifs et à hauts degrés d’oxydation tel que les métaux du groupe 13. L’optimisation de voies de synthèse a permis d’étendre le nombre de complexes de types NHC-MIII (M = aluminium, gallium et indium), ainsi qu’à des complexes cationiques. L’association de ces précurseurs avec des NHCs plus encombrés a permis l’observation de réactivités sans précédent (complexes anormaux, paires de Lewis frustrées, dicarbènes N-hétérocycliques). Dans un second temps, la réactivité inhabituelle des ligands NHCs a permis l’isolation d’analogue au réactif de Tebbe, très actifs en méthylénation de dérivés carbonylesAt the beginning of this work, few studies had been performed on the complexation of N-heterocyclic carbenes with oxophilic metals, in high oxidation states such as group 13 metals. The synthetic routes optimization has extended the number of complexes-type NHC-MIII (M = aluminum, gallium and indium), and the corresponding cationic complexes. The combination of these precursors with sterically congested NHCs allowed the observation of unprecedented reactivities (abnormal complexes, Frustrated Lewis Pairs, N-heterocyclic dicarbenes). In a second step, the unusual reactivity of NHC ligands has allowed the isolation of analogues of the Tebbe’s reagent, formed to be very active in the methylenation of carbonyl compounds
10
Garrison, Jered C. "Silver N-Heterocyclic Carbenes." University of Akron / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=akron1124128998.
Books on the topic "Carbène NHC":
1
Estates, NHS, ed. Carbon/energy management in healthcare: Best practice advice for the NHS in England on meeting the mandatory carbon/energy targets, March 2000-March 2010. London: Stationery Office, 2004.
2
United States. National Aeronautics and Space Administration., ed. Analysis of minerals containing dissolved taraces of the fluid phase components "water" and "carbon dioxide": Final report submitted to the NASA Ames Research Center for NASA cooperative agreement NCC 2-446. Mountain View, CA: SETI Institute, 1991.
3
Jaramillo, Marcela, and Valentina Saavedra. NDC Invest: Supporting Transformational Climate Policy and Finance. Inter-American Development Bank, 2021. http://dx.doi.org/10.18235/0003340.
Abstract:
The Inter-governmental Panel on Climate Change (IPCC) indicates that meeting the Paris Agreement's goal of limiting the global temperature rise from pre-industrial levels to between 1.5 and 2 degrees Celsius requires reaching net-zero emissions of carbon dioxide (CO2) between 2050 and 2070, as well as deep reductions in the emissions of other greenhouse gases by around mid-century (GHGs) (IPCC, 2018). At the same time countries need to build resilience to face the changes that cannot be avoided. NDC Invest was created as the one-stop-shop of the IDB Group providing technical and financial support for countries in Latin American and Caribbean (LAC) in their efforts to achieve the climate objectives under the Paris Agreement, seeking to transition to a net zero, resilient and sustainable development pathways that improve quality of life and prosperity in LAC. Through our research and experience supporting countries and piloting solutions we have developed a toolbox for support. This paper describes three NDC Invest products to support Governments to tackle challenges and scale up action towards a climate aligned and sustainable development path: i) the design of Long-Term Strategies (LTS) for net-zero emissions and resilience; ii) design of ambitious Nationally Determined Contributions (NDCs), aligned to LTS; and iii) design of investment plans and finance strategies. Our three products are not a fix recipe, but rather a toolbox to provide flexible and relevant solutions tailored to country needs and context, and different stages of design and implementation of their climate targets.
4
Great Britain: Department of Health: Estates and Facilities Division. Statistics on energy performance and carbon and CO2 Emissions: NHS England, 1999/00 to 2004/05. Stationery Office, The, 2006.
5
Strand, Jon. Climate Finance, Carbon Market Mechanisms and Finance “Blending” as Instruments to Support NDC Achievement under the Paris Agreement. World Bank, Washington, DC, 2019. http://dx.doi.org/10.1596/1813-9450-8914.
6
Eland, John H. D., and Raimund Feifel. Molecules with four, five or seven atoms. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198788980.003.0005.
Abstract:
Double photoionisation spectra of NH3, C2H2, HCHO, C2N2, PCl3, CH4, the methyl halides CH3F, CH3Cl, CH3I, the methylene halides CH2Cl2, CH2Br2, CH2I2, the carbon tetrahalides CF4, CCl4, CBr4, germanium tetrahalides GeCl4, GeBr4, and SF6 are presented with analysis to identify the electronic states of the doubly charged ions. The effects of indirect double ionisation pathways are discussed. There are relatively few important molecules with just four atoms, but most of the ones included here are present and sometimes abundant in planetary and astrophysical environments. The range of five-atom molecules includes methane and all its simple derivatives. Where possible closely related molecules are grouped together in this chapter, as much of the discussion of their electronic structure is the same for all members of a group. This chapter also includes SF6 as a closely related molecule, even though its atom count goes beyond those of some molecules in later chapters.
7
Marques, Marcia, ed. Estudos Avançados em Engenharia Civil. Bookerfield Editora, 2022. http://dx.doi.org/10.53268/bkf21111100.
Abstract:
No Brasil a Engenharia Civil se utiliza de ciência aplicada na execução de ações indispensáveis prestadas à sociedade. Além da grande área das Engenharias, sua abrangência multidisciplinar frequentemente colabora com as demais áreas do conhecimento com soluções em benefício da sociedade. Este livro reúne capítulos que trazem importantes avanços relacionados a estruturas, construção civil, eletrotécnica, hidráulica ambiental e geotecnia. Visando uma melhor organização, os capítulos estão agrupados nas seções: Ciência Onshore e Ciência Offshore. A seção de Ciência Onshore é composta por cinco capítulos. Pelo primeiro capítulo é avaliada a resistência e a rigidez de diafragmas horizontais, construídos em Sistemas Leves de Madeira. Foram ensaiados protótipos em escala real com diferentes arranjos construtivos concluindo-se que o emprego de dispositivos enrijecedores permite o aumento da resistência e rigidez dos diafragmas. O segundo capítulo aborda construções em madeira sob a ótica de sistemas com estruturas leves, apresentando análise computacional através de modelagem pelo método de elementos finitos. As análises demonstraram que a flecha real e a calculada para as vigas individuais, que compõem o diafragma de piso, apresentam reduções que variam de 18 a 30% quando comparadas com valores calculados para vigas isoladas. No contexto dos sistemas construtivo e estrutural da Construção Civil, observa-se uma inevitável e progressiva tendência de substituição dos sistemas convencionais por sistemas industrializados. Por meio do terceiro capítulo é apresentada uma revisão bibliográfica sobre conceitos de construção industrializada, abordando o atual cenário técnico no Brasil, e confrontando algumas das principais tecnologias industrializadas presentes hoje no segmento da Construção Civil. O quarto capítulo trata da engenharia aplicada ao ambiente offshore e apresenta uma análise de fadiga estrutural de conexões entre um reforçador longitudinal do costado e uma antepara transversal de uma unidade flutuante de produção, armazenamento e transferência (FPSO) convertida a partir de um navio petroleiro, sendo possível estimar a vida remanescente do FPSO. Por meio do capítulo cinco são apresentados detalhes de um reforço estrutural utilizando polímero reforçado com fibra de carbono (PRFC) em uma plataforma offshore de concreto armado. Apesar de adotada uma técnica consolidada, pouco se sabe sobre o desempenho do reforço ao longo do tempo quando exposto ao ambiente marinho. Pelo capítulo é apresentado um panorama geral da estrutura após 17 anos da execução do reforço que comprovou o bom desempenho da técnica empregada. A seção de Ciência Offshore é composta por quatro capítulos. Pelo capítulo seis é abordada a utilização de sistemas solares fotovoltaicos conectados à rede (SFVCR), enquanto apresenta uma proposta de metodologia para avaliar o potencial fotovoltaico para a Região Metropolitana de Curitiba. Foi realizado ainda, um levantamento do montante de gases de efeito estufa que são deixados de emitir. O capítulo contribui para a implantação de políticas públicas de incentivo para esta fonte energética. Geopolímeros são materiais alternativos ao cimento Portland, apresentando alta resistência mecânica e durabilidade química e térmica. Pelo capítulo sete são avaliadas as propriedades mecânicas de argamassas geopoliméricas contendo adição de Nanotubos de Carbono (NTC) assim como o método de incorporação do nanocompósito a argamassa. Os resultados mostram que os NTC quando bem distribuídos na matriz promovem um aumento de resistência à compressão e flexão das amostras. O capítulo oito trata do fetch, importante elemento na quantificação de fenômenos gerados pelo vento em reservatórios de Usinas Hidrelétricas. A abordagem apresentada amplia a compreensão do fetch através de um conceito bidimensional via processamento computacional, permitindo a geração de mapas e a determinação segura dos valores máximos para cada direção e a localização dos maiores comprimentos para o reservatório de Tucuruí, este importante reservatório no Brasil. Na quantificação dos fenômenos hidrodinâmicos em lagos e reservatórios é frequente a necessidade de conhecer o alcance das perturbações alcançadas pelas ondas ao se propagarem. Este fenômeno está relacionado à ressuspensão de sedimentos, desestratificação térmica, e erosão das margens, afetando o ecossistema aquático, as cadeias produtivas aquícolas e a vida útil de componentes mecânicos das UHE’s. Por meio do capítulo nono é apresentado o conceito de profundidade de mistura aplicado ao reservatório da hidrelétrica de Lajeado, Tocantins. É realizado o mapeamento das profundidades máximas perturbadas pelas ondas de vento ao se propagarem, contribuindo para uma melhor compreensão da estratificação térmica e da ressuspensão de sedimentos no reservatório desta importante usina hidrelétrica.
Book chapters on the topic "Carbène NHC":
1
Louie, Janis. "Ni-NHC Mediated Catalysis." In N-Heterocyclic Carbenes in Synthesis, 163–82. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2006. http://dx.doi.org/10.1002/9783527609451.ch7.
2
Lazreg, Faïma, and Catherine S. J. Cazin. "NHC-Copper Complexes and their Applications." In N-Heterocyclic Carbenes, 199–242. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2014. http://dx.doi.org/10.1002/9783527671229.ch08.
3
Chauhan, Pankaj, Suruchi Mahajan, Xiang-Yu Chen, and Dieter Enders. "Domino Processes in NHC Catalysis." In N-Heterocyclic Carbenes in Organocatalysis, 133–56. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2019. http://dx.doi.org/10.1002/9783527809042.ch5.
4
Jin, Zhichao, Xingkuan Chen, and Yonggui R. Chi. "Recent Activation Modes in NHC Organocatalysis." In N-Heterocyclic Carbenes in Organocatalysis, 187–212. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2019. http://dx.doi.org/10.1002/9783527809042.ch7.
5
Nagao, Kazunori, and Hirohisa Ohmiya. "N‑Heterocyclic Carbene (NHC)/Metal Cooperative Catalysis." In Asymmetric Organocatalysis Combined with Metal Catalysis, 83–97. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-43851-7_4.
6
Chen, Xiangyu. "NHC-Catalyzed Annulations of Nitroalkenes." In New Strategies for N-Heterocyclic Carbenes Catalyzed Annulations, 29–61. Singapore: Springer Singapore, 2016. http://dx.doi.org/10.1007/978-981-10-2899-1_2.
7
Lazreg, Faïma, and Catherine S. J. Cazin. "Medical Applications of NHC-Gold and -Copper Complexes." In N-Heterocyclic Carbenes, 173–98. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2014. http://dx.doi.org/10.1002/9783527671229.ch07.
8
Wurm, Thomas, Abdullah Mohamed Asiri, and A. Stephen K. Hashmi. "NHC-Au(I) Complexes: Synthesis, Activation, and Application." In N-Heterocyclic Carbenes, 243–70. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2014. http://dx.doi.org/10.1002/9783527671229.ch09.
9
Díez-González, Silvia, and Steven P. Nolan. "Palladium-catalyzed Reactions Using NHC Ligands." In N-Heterocyclic Carbenes in Transition Metal Catalysis, 47–82. Berlin, Heidelberg: Springer Berlin Heidelberg, 2006. http://dx.doi.org/10.1007/978-3-540-36930-1_3.
10
Chen, Xiangyu. "NHC-Catalyzed Enantioselective Annulations of Enals." In New Strategies for N-Heterocyclic Carbenes Catalyzed Annulations, 63–85. Singapore: Springer Singapore, 2016. http://dx.doi.org/10.1007/978-981-10-2899-1_3.
Conference papers on the topic "Carbène NHC":
1
Ou, Juan, Ruomiao Yang, Yuchao Yan, Zhentao Liu, and Jinlong Liu. "Investigation of the Effect of Ammonia Addition on the Two-Stage Ignition Process of Dimethyl Ether Based on Chemical Kinetic Analysis." In ASME 2023 ICE Forward Conference. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/icef2023-110108.
Abstract:
Abstract Ammonia (NH3) has garnered considerable attention in recent years as a promising carbon-free hydrogen carrier fuel for internal combustion engines. However, directly using pure ammonia in compression-ignition engines poses challenges. To facilitate NH3 ignition, high-activity fuels are often employed to ignite the premixed NH3/air mixture and initiate combustion. This study specifically focuses on the ignition process of binary mixtures of NH3 and dimethyl ether (DME), considering that DME is a carbon-neutral high-activity fuel. By conducting zero-dimensional reaction kinetics analysis, we compare the ignition processes of DME and NH3/DME mixtures. The results reveal that the addition of NH3 has minimal impact on the control mechanism of DME’s two-stage ignition process. DME still heavily relies on the proliferation of OH radicals in the low-temperature oxidation pathway, releasing heat during the reaction progression. As the temperature increases, the low-temperature oxidation branching pathways are gradually replaced by chain propagation pathways, resulting in a decrease in overall reaction activity. The reactivity and temperature rise rate of the reaction system is then controlled by the H2O2 loop mechanism prior to the thermal ignition. However, the presence of ammonia noticeably extends the ignition delay period of DME. Ammonia competes with OH radicals, essential for DME oxidation, thereby inhibiting DME ignition. Additionally, as the ignition reaction advances, the involvement of NH3 kinetics increases. For instance, nitrogen-containing species generated from NH3 oxidation, such as NO, NO2, and NH2, react with CH3OCH2 to form CH3OCHO, reducing the flux through the low-temperature oxidation pathway of DME. While ammonia reaction pathways also generate OH radicals, this comes at the expense of HO2 radicals and H radicals, ultimately leading to H2O2 production. Overall, these findings clearly demonstrate the substantial impact of ammonia addition on the ignition process of DME, emphasizing the necessity for further fundamental research to enhance our understanding of NH3/DME binary fuel ignition. Such insights are pivotal for improving the design and operation strategies of NH3/DME dual-fuel engines, thereby improving engine efficiency and reliability.
2
Isa, Siti S. Mat, Muhammad M. Ramli, M. F. Jamlos, N. A. M. Ahmad Hambali, M. Mohamad Isa, S. R. Kasjoo, N. Ahmad, N. I. M. Nor, and N. Khalid. "Multi-walled carbon nanotubes plastic NH3 gas sensor." In 11TH ASIAN CONFERENCE ON CHEMICAL SENSORS: (ACCS2015). Author(s), 2017. http://dx.doi.org/10.1063/1.4975263.
3
Faudzi, Najwa Mohd, Ahmad Rashidy Razali, Asrulnizam Abd Manaf, Nurul Huda Abd Rahman, Ahmad Azlan Aziz, Amiruddin Ibrahim, and Aiza Mahyuni Mozi. "Characterization of Carbon-based NFC Tag Antenna Design." In 2022 IEEE International RF and Microwave Conference (RFM). IEEE, 2022. http://dx.doi.org/10.1109/rfm56185.2022.10065256.
4
Pugh, D., A. Valera-Medina, P. Bowen, A. Giles, B. Goktepe, J. Runyon, S. Morris, S. Hewlett, and R. Marsh. "Emissions Performance of Staged Premixed and Diffusion Combustor Concepts for an NH3/Air Flame With and Without Reactant Humidification." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14953.
Abstract:
Abstract Renewably generated ammonia offers a form of carbon-free chemical energy storage to meet the differences between uncertain renewable supply and fluctuating demand, and has the potential to support future energy requirements as a power-to-X concept. The storage and transportation characteristics of NH3 are favorable compared with H2, however there are significant combustion research challenges to enhance fuel reactivity whilst reducing harmful emissions production. The purpose of the presented work was to evaluate different fuel delivery concepts for a representative GT combustor. An experimental and numerical comparison was made between swirl-stabilized premixed and diffusion NH3-air flames at elevated inlet temperature (473 K). The exhaust NOx and unburned NH3 emissions generated from each concept were quantified to optimize operational combustor performance. High-speed OH* and NH2* chemiluminescence was employed to characterize the change in flame topology with variation in fuel-air equivalence ratio, and the resultant influence on measured emission concentrations. Chemiluminescence intensities were shown to elucidate changes in sampled exhaust emissions, enabling detailed analysis of intermediate chemistry. A comparison was made between experimental data and chemical kinetic simulations with a reactor network model, demonstrating the sensitivity of NOx emissions to premixed fuel-air equivalence ratio. A comparison was also made between exclusive primary airflow, and the staged introduction of secondary air, to quantify the change in NOx production between each configuration and improve fuel burnout. Secondary air loadings were incrementally increased through the combustor, and the change in exhaust emissions mapped. In addition, reactant humidification was employed as a secondary process for NOx reduction, having shown favorable performance with NH3/H2 mixtures to limit thermochemical NO production. The efficacy of humidification was compared for both premixed and diffusion configurations.
5
Rai, A. K., R. S. Bhattacharya, M. Massey, O. L. Eryilmaz, and A. Erdemir. "Evaluation of Near Frictionless Carbon Coatings Using Four-Ball Wear Tester." In World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-63867.
Abstract:
Near frictionless carbon (NFC) coatings were deposited in a large-area filtered cathodic arc system by plasma-enhanced chemical vapor deposition. An NFC coating with carbon-enriched TiC bond layers was deposited on half inch diameter steel (M50) balls. The four-ball wear test was used to evaluate the performance of the NFC coating. The endurance limit of the NFC coating was determined by starting the wear test at a relatively low load and increasing the load by a fixed amount after a given time interval to a final load at which the friction force reached a certain level. The four-ball wear test was conducted in fully flooded, starved, and dry lubrication conditions. MIL-PRF-23699 oil was the lubricant. Test results indicated a much higher endurance limit for the NFC-coated balls compared to that of uncoated balls.
6
Dandeliya, Sushmita, and Anurag Srivastava. "Carbon Nanotube Based NH3 Gas Sensor: Ab-Initio Study." In 2015 IEEE International Symposium on Nanoelectronic and Information Systems (iNIS). IEEE, 2015. http://dx.doi.org/10.1109/inis.2015.54.
7
Zhang, Songlin, Ayou Hao, Nam Nguyen, Abiodun Oluwalowo, Juhil Mahendra Ahir Ahir, Zhe Liu, Yourri Dessureault, Jin Gyu Park, and Richard Liang. "Pyrolyzed Polydopamine (py-pda) Functionalized Carbon Nanotubes and their Carbon/Carbon Composite with Improved Mechanical and Electrical Properties." In SAMPE 2019 - Charlotte, NC. SAMPE, 2019. http://dx.doi.org/10.33599/nasampe/s.19.1510.
8
Mohammadpour, Ehsan, and Mokhtar Awang. "A finite element model for predicting the tensile behavior of carbon naotube." In 2011 National Postgraduate Conference (NPC). IEEE, 2011. http://dx.doi.org/10.1109/natpc.2011.6136394.
9
Hasnahena, S. T., Biswarup Satpati, and Madhusudan Roy. "Enhanced sensing of NH3 gas by decorated multiwalled carbon nanotube." In DAE SOLID STATE PHYSICS SYMPOSIUM 2015. Author(s), 2016. http://dx.doi.org/10.1063/1.4947749.
10
Endot, Nor Azam, and Ye Lwin. "Characterization of novel solvothermolysed dolomite for carbon dioxide separation from synthetic gas mixture." In 2011 National Postgraduate Conference (NPC). IEEE, 2011. http://dx.doi.org/10.1109/natpc.2011.6136277.
Reports on the topic "Carbène NHC":
1
Fazekas, Andreas, and Scarleth Nuñez Castillo. NDC Invest Annual Overview 2020. Inter-American Development Bank, July 2021. http://dx.doi.org/10.18235/0003430.
Abstract:
NDC INVEST is an IDB Group platform offering financial solutions and technical support to help build national goals and transform them into attainable plans that generate prosperous, resilient, and carbon neutral economies. Throughout the years closely supporting LAC countries, NDC INVEST has gained valuable experience and knowledge in designing and implementing concrete actions that lead to long-term climate resilience and net-zero emissions by 2050. In 2020, NDC INVEST confirmed its key role in successfully translating national climate commitments into physical and beneficial economic plans and transformational development projects. 331 initiatives have been supported in IDB Group regional member states through the IDB sovereign window, IDB Invest and IDB Lab. This publication highlights the successful work of NDC Invest in i.) developing relevant knowledge and building national capacities for long-term strategies (LTS), ii.) supporting countries in creating ambitious climate goals and NDCs, and iii.) implementing LTS and NDCs through financial strategies and investment plans.
2
Chepeliev, Maksym. Development of the Air Pollution Database for the GTAP 10A Data Base. GTAP Research Memoranda, June 2020. http://dx.doi.org/10.21642/gtap.rm33.
Abstract:
The purpose of this note is to document data sources and steps used to develop the air pollution database for the GTAP Data Base Version 10A. Emissions for nine substances are reported in the database: black carbon (BC), carbon monoxide (CO), ammonia (NH3), non-methane volatile organic compounds (NMVOC), nitrogen oxides (NOx), organic carbon (OC), particulate matter 10 (PM10), particulate matter 2.5 (PM2.5) and sulfur dioxide (SO2). The dataset covers four reference years – 2004, 2007, 2011 and 2014. EDGAR Version 5.0 database is used as the main data source. To assist with emissions redistribution across consumption-based sources, IIASA GAINS-based model and IPCC-derived emission factors are applied. Each emission flow is associated with one of the four sets of emission drivers: output by industries, endowment by industries, input use by industries and household consumption. In addition, emissions from land use activities (biomass burning) are estimated by land cover types. These emissions are reported separately without association with emission drivers.
3
Gasim, Anwar, Lester C. Hunt, and Jeyhun Mikayilov. Baseline Forecasts of Carbon Dioxide Emissions for Saudi Arabia Using the Structural Time Series Model and Autometrics. King Abdullah Petroleum Studies and Research Center, May 2023. http://dx.doi.org/10.30573/ks--2022-dp19.
Abstract:
To tackle the threat of climate change, countries worldwide have signed the Paris Agreement. This agreement aims to limit the global average temperature increase to below 2 degrees Celsius and potentially below 1.5 degrees Celsius above pre-industrial levels (UNFCCC 2015). Parties to the Paris Agreement are required to submit domestic climate plans detailing their mitigation measures, known as nationally determined contributions (NDCs). These plans detail countries’ ambitions and efforts to combat and respond to climate change. NDCs are communicated at five-year intervals, and each successive NDC must represent an increase in ambition over the previous one.
4
Chepeliev, Maksym, Israel Osorio Rodarte, and Dominique van der Mensbrugghe. Distributional Impacts of Carbon Pricing Policies under Paris Agreement: Inter and Intra-Regional Perspectives. GTAP Working Paper, February 2021. http://dx.doi.org/10.21642/gtap.wp88.
Abstract:
While bringing multiple benefits for the environment, achievement of the stringent global greenhouse gas emissions reduction target, like the one outlined in the Paris Climate Agreement, is associated with significant implementation costs and could impact different dimensions of human well-being, including welfare, poverty and distributional aspects. In this paper, we analyze the poverty and distributional impacts of different carbon pricing mechanisms consistent with reaching the Paris Agreement targets. We link a global recursive dynamic computable general equilibrium model ENVISAGE with the GIDD microsimulation model and explore three levels of mitigation effort and five carbon pricing options (trade coalitions). Results suggest that while there is a higher incidence of poverty in all scenarios, mainly driven by lower economic growth, Nationally Determined Contribution (NDC) policies result in progressive income distribution at the global level. Such progressivity is caused not only by lower relative prices of food versus non-food commodities, but also by a general decline in skill wage premia.
5
Blair, Neal. A benthic carbon budget for the Continental Slope off Cape Hatteras, NC. Office of Scientific and Technical Information (OSTI), December 1999. http://dx.doi.org/10.2172/765626.
6
Kalman, Joseph, and Maryam Haddad. Wastewater-derived Ammonia for a Green Transportation Fuel. Mineta Transportation Institute, July 2022. http://dx.doi.org/10.31979/mti.2021.2041.
Abstract:
The energy-water nexus (i.e., availability of potable water and clean energy) is among the most important problems currently facing society. Ammonia is a carbon-free fuel that has the potential to reduce the carbon footprint in combustion related vehicles. However, ammonia production processes typically have their own carbon footprint and do not necessarily come from sustainable sources. This research examines wastewater filtration processes to harvest ammonia for transportation processes. The research team studied mock wastewater solutions and was able to achieve ammonia concentrations above 80%(nanofiltration) and 90% (reverse osmosis). The research team also investigated the influence of transmembrane pressure and flow rates. No degradation to the membrane integrity was observed during the process. This research used constant pressure combustion simulations to calculate the ignition delay times for NH3-air flames with expected impurities from the wastewater treatment processes. The influence of impurities, such as H2O, CO, CO2, and HCl, were studied under a range of thermodynamic conditions expected in compression ignition engines. The team observed carbon monoxide and water vapor to slightly decrease (at most 5%) ignition delay time, whereas HCl, in general, increased the ignition delay. The changes to the combustion chemistry and its influence of the reaction mechanism on the results are discussed. The experimental wastewater treatment study determined that reverse osmosis produced higher purity ammonia. The findings of the combustion work suggest that ignition delays will be similar to pure ammonia if HCl is filtered from the final product.
7
Kalman, Joseph, and Maryam Haddad. Wastewater-derived Ammonia for a Green Transportation Fuel. Mineta Transportation Institute, July 2022. http://dx.doi.org/10.31979/mti.2022.2041.
Abstract:
The energy-water nexus (i.e., availability of potable water and clean energy) is among the most important problems currently facing society. Ammonia is a carbon-free fuel that has the potential to reduce the carbon footprint in combustion related vehicles. However, ammonia production processes typically have their own carbon footprint and do not necessarily come from sustainable sources. This research examines wastewater filtration processes to harvest ammonia for transportation processes. The research team studied mock wastewater solutions and was able to achieve ammonia concentrations above 80%(nanofiltration) and 90% (reverse osmosis). The research team also investigated the influence of transmembrane pressure and flow rates. No degradation to the membrane integrity was observed during the process. This research used constant pressure combustion simulations to calculate the ignition delay times for NH3-air flames with expected impurities from the wastewater treatment processes. The influence of impurities, such as H2O, CO, CO2, and HCl, were studied under a range of thermodynamic conditions expected in compression ignition engines. The team observed carbon monoxide and water vapor to slightly decrease (at most 5%) ignition delay time, whereas HCl, in general, increased the ignition delay. The changes to the combustion chemistry and its influence of the reaction mechanism on the results are discussed. The experimental wastewater treatment study determined that reverse osmosis produced higher purity ammonia. The findings of the combustion work suggest that ignition delays will be similar to pure ammonia if HCl is filtered from the final product.
8
Nicholson, Claire, Jonathan Wastling, Peter Gregory, and Paul Nunn. FSA Science Council Working Group 6 Food Safety and Net Zero Carbon July 2022 Interim Report. Food Standards Agency, July 2022. http://dx.doi.org/10.46756/sac.fsa.vxz377.
Abstract:
The UK has a legal commitment to reach net zero carbon (NZC) emissions by 2050. This is a topic that has recently been building momentum, with clean growth being one of the four Grand Challenges set out by the UK Government. The ways we grow, process and transport food are major contributors to climate change, accounting for more than a quarter of all greenhouse gas emissions. Reducing this will require substantial changes in agriculture, manufacturing, and transport. Consequently, the Science Council and FSA Chief Scientific Adviser (CSA) agreed that a deeper understanding of the potential implications of achieving net zero on food systems, together with identification of areas of uncertainty, would be of considerable value to FSA in pre-empting future policy and evidence needs in this area. In early discussions to scope the work required, Defra indicated to the FSA Science Council Secretariat that there are many new developments and changes to activity in primary production aimed at achieving net zero. The Science Council agreed, therefore, to concentrate its first investigations on changes expected in primary food production. Primary production is the production of chemical energy in organic forms by living organisms. The main source of this energy is sunlight. For the purposes of this review, primary food production includes the growing and harvesting of plants as food for humans or feed for animals, and the rearing and slaughter of animals including livestock, fish and a wide variety of aquatic and marine organisms. A Science Council Working Group 6 (WG6) began work in summer 2021, led by Science Council members Mrs Claire Nicholson (WG6 Chair) and Prof Jonathan Wastling (WG6 Deputy Chair). The brief for WG6 is to investigate the potential food safety implications arising from changes to primary food production practices and technologies that reduce carbon emissions in the next 10 years. The work programme (described in this report) covers 4 phases, with phases 1 and 2 now complete. The work so far has drawn diverse, wide-ranging, sometimes slightly conflicting, views and opinions from across academia, the FSA, Defra, industry bodies and individual food producers. This interim report summarises: The work undertaken to date (phases 1 and 2) What has been learnt including changes to practice already underway or imminent Issues arising from the changes that the FSA should be aware of Further work planned by WG6 to understand the nature of the risks in more depth (phases 3 and 4) The Science Council aims to complete its investigations by the end of 2022 and present its findings to the FSA Board as soon as possible afterwards.
9
Gummow. L51908 AC Grounding Effects on Cathodic Protection Performance in Pipeline Stations.pdf. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), December 2001. http://dx.doi.org/10.55274/r0010269.
Abstract:
Most AC powered equipment at pipeline stations and at motorized valve sites isrequired, by code, to be electrically grounded to one or more ground electrodes. These grounding systems are normally electrically bonded to the AC power distribution grid, which can be quite extensive. Piping, either intentionally or inadvertently, is often connected to the AC electrical grounding grid in pipeline stations. Grounding grid conductors are usually bare and composed of copper or tinned copper, and ground rod materials can consist of a wide variety of metals such as copper-clad steel, carbon steel, stainless steel, galvanized steel, and galvanic anode alloys of zinc and magnesium. The interconnection of these grounding materials to the piping can increase the current requirements of the cathodic protection system, distort the current distribution pattern and complicate the accurate measurement of the pipe potentials. Benefit: The primary objective of this research project was to assess the impact of various types of grounding materials on the performance and testing of cathodic protection systems. The two major issues in this regard were the effects on current requirements and the accuracy of pipe-to-soil potential measurements. In addition, some related issues investigated as follows:the electrical resistance of each groundrod-to-earth was to be measured to determine whether or not there were any changes in the resistance-to-earth as a result cathodic polarization;the potential of galvanized steel was to be measured with increasing zinc consumption to determine if there is a well defined relationship between potential and zinc consumption; the National Electrical Code (NEC) was to be reviewed with respect to the insertion of AC coupling/DC isolating devices in series between the piping and the electrical grounding network. The results of this investigation were intended toprovide information to design more effective cathodic protection facilities for piping in pipeline stations having electrical grounding systems, anddetermine whether or not the resistance of the electrical grounding system increases as a result of receiving cathodic protection, andrecommend pipe-to-soil potential survey techniques to maximize measurement accuracy in the presence of an AC grounding grid, andevaluate the use of DC isolators/AC couplers to interconnect the piping to either the secondary or primary AC grounding system.
10
Phuong, Vu Tan, Nguyen Van Truong, and Do Trong Hoan. Commune-level institutional arrangements and monitoring framework for integrated tree-based landscape management. World Agroforestry, 2021. http://dx.doi.org/10.5716/wp21024.pdf.
Abstract:
Governance is a difficult task in the context of achieving landscape multifunctionality owing to the multiplicity of stakeholders, institutions, scale and ecosystem services: the ‘many-multiple’ (Cockburn et al 2018). Governing and managing the physical landscape and the actors in the landscape requires intensive knowledge and good planning systems. Land-use planning is a powerful instrument in landscape governance because it directly guides how actors will intervene in the physical landscape (land use) to gain commonly desired value. It is essential for sustaining rural landscapes and improving the livelihoods of rural communities (Bourgoin and Castella 2011, Bourgoin et al 2012, Rydin 1998), ensuring landscape multifunctionality (Nelson et al 2009, Reyers et al 2012) and enhancing efficiency in carbon sequestration, in particular (Bourgoin et al 2013, Cathcart et al 2007). It is also considered critical to the successful implementation of land-based climate mitigation, such as under Nationally Determined Contributions (NDCs), because the Land Use, Land-Use Change and Forestry (LULUCF) sector is included in the mitigation contributions of nearly 90 percent of countries in Sub-Saharan and Southern Asia countries and in the Latin American and Caribbean regions (FAO 2016). Viet Nam has been implementing its NDC, which includes forestry and land-based mitigation options under the LULUCF sector. The contribution of the sector to committed national emission reduction is significant and cost-effective compared with other sectors. In addition to achieving emission reduction targets, implementation of forestry and land-based mitigation options has the highest benefits for social-economic development and achieving the Sustainable Development Goals (MONRE 2020). Challenges, however, lie in the way national priorities and targets are translated into sub-national delivery plans and the way sub-national actors are brought together in orchestration (Hsu et al 2019) in a context where the legal framework for climate-change mitigation is elaborated at national rather than sub-national levels and coordination between government bodies and among stakeholders is generally ineffective (UNDP 2018). In many developing countries, conventional ‘top–down’, centralized land-use planning approaches have been widely practised, with very little success, a result of a lack of flexibility in adapting local peculiarities (Amler et al 1999, Ducourtieux et al 2005, Kauzeni et al 1993). In forest–agriculture mosaic landscapes, the fundamental question is how land-use planning can best conserve forest and agricultural land, both as sources of economic income and environmental services (O’Farrell and Anderson 2010). This paper provides guidance on monitoring integrated tree-based landscape management at commune level, based on the current legal framework related to natural resource management (land and forest) and the requirements of national green-growth development and assessment of land uses in two communes in Dien Bien and Son La provinces. The concept of integrated tree based landscape management in Viet Nam is still new and should be further developed for wider application across levels.