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Статті в журналах з теми "NHC Ligand"
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Rais, Eduard, Ulrich Flörke та René Wilhelm. "Crystal structures of diiodidobis[(1S,5S)-4-mesityl-1,2,8,8-tetramethyl-2,4-diazabicyclo[3.2.1]octan-3-ylidene-κC3]palladium(IV) and dichlorido[(1S,5S)-4-mesityl-1,2,8,8-tetramethyl-2,4-diazabicyclo[3.2.1]octan-3-ylidene-κC3](triphenylphosphane-κP)palladium(IV)". Acta Crystallographica Section E Crystallographic Communications 71, № 8 (11 липня 2015): 919–22. http://dx.doi.org/10.1107/s2056989015013055.
Повний текст джерелаАнотація:
The molecular structures of the chiral title compounds, [Pd(C19H28N2)2I2], (I), and [Pd(C19H28N2)Cl2(C18H15P)], (II), show a distorted square-planar coordination around the PdIIatoms with two halogenide (Hal) ligands each and two N-heterocyclic carbene (NHC) ligands in (I) or one NHC and one triphenylphosphane ligand in (II). The deviations of the PdIIatoms from theL2Hal2best plane (L= NHC or triphenylphosphane ligand) are 0.206 (1) Å for (I) and 0.052 (1) Å for (II). The crystal packings exhibit intermolecular C—H...Hal hydrogen bonds.
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Diesel, Johannes, and Nicolai Cramer. "Modular Chiral N-Heterocyclic Carbene Ligands for the Nickel-Catalyzed Enantioselective C–H Functionalization of Heterocycles." CHIMIA International Journal for Chemistry 74, no. 4 (April 29, 2020): 278–84. http://dx.doi.org/10.2533/chimia.2020.278.
Повний текст джерелаАнотація:
N-Heterocyclic carbenes (NHCs) are the ligands of choice in a large variety of transformations entailing different transition metals. However, the number and variety of chiral NHCs suitable as stereo-controlling ligands in asymmetric catalysis remains limited. Herein we highlight the introduction of a modular NHC ligand family, consisting of a chiral version of the widely used IPr ligand. These chiral NHC ligands were applied in the nickel-catalyzed enantioselective C–H functionalization of N-heterocycles. Nickel-NHC catalysis unlocked the stereoselective C–H annulation of 2- and 4-pyridones, delivering fused bicyclic compounds found in many biologically active compounds. Applying a bulky, yet flexible ligand scaffold enabled the highly enantioselective C–H functionalization of pyridones under mild conditions. The introduction of a bulky chiral SIPr analogue enabled the nickel-catalyzed enantioselective C–H functionalization of indoles, yielding valuable tetrahydropyridoindoles. Additionally, pyrrolopyridines, pyrrolopyrimidines and pyrroles were efficiently functionalized, delivering chiral annulated azoles.
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Iannuzzi, Theresa E., Yafei Gao, Tessa M. Baker, Liang Deng, and Michael L. Neidig. "Magnetic circular dichroism and density functional theory studies of electronic structure and bonding in cobalt(ii)–N-heterocyclic carbene complexes." Dalton Transactions 46, no. 39 (2017): 13290–99. http://dx.doi.org/10.1039/c7dt01748k.
Повний текст джерелаАнотація:
The combination of simple cobalt salts and N-heterocyclic carbene (NHC) ligands has been highly effective in C–H functionalization, hydroarylation and cross-coupling catalysis, though displaying a strong dependence on the identity of the NHC ligand.
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Dröge, Thomas, and Frank Glorius. "NHC - Ligand der Ideen." Nachrichten aus der Chemie 58, no. 2 (February 2010): 112–17. http://dx.doi.org/10.1002/nadc.201069673.
Повний текст джерела
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Suresh, Lakshmi, Ralte Lalrempuia, Jonas B. Ekeli, Francis Gillis-D’Hamers, Karl W. Törnroos, Vidar R. Jensen, and Erwan Le Roux. "Unsaturated and Benzannulated N-Heterocyclic Carbene Complexes of Titanium and Hafnium: Impact on Catalysts Structure and Performance in Copolymerization of Cyclohexene Oxide with CO2." Molecules 25, no. 19 (September 23, 2020): 4364. http://dx.doi.org/10.3390/molecules25194364.
Повний текст джерелаАнотація:
Tridentate, bis-phenolate N-heterocyclic carbenes (NHCs) are among the ligands giving the most selective and active group 4-based catalysts for the copolymerization of cyclohexene oxide (CHO) with CO2. In particular, ligands based on imidazolidin-2-ylidene (saturated NHC) moieties have given catalysts which exclusively form polycarbonate in moderate-to-high yields even under low CO2 pressure and at low copolymerization temperatures. Here, to evaluate the influence of the NHC moiety on the molecular structure of the catalyst and its performance in copolymerization, we extend this chemistry by synthesizing and characterizing titanium complexes bearing tridentate bis-phenolate imidazol-2-ylidene (unsaturated NHC) and benzimidazol-2-ylidene (benzannulated NHC) ligands. The electronic properties of the ligands and the nature of their bonds to titanium are studied using density functional theory (DFT) and natural bond orbital (NBO) analysis. The metal–NHC bond distances and bond strengths are governed by ligand-to-metal σ- and π-donation, whereas back-donation directly from the metal to the NHC ligand seems to be less important. The NHC π-acceptor orbitals are still involved in bonding, as they interact with THF and isopropoxide oxygen lone-pair donor orbitals. The new complexes are, when combined with [PPN]Cl co-catalyst, selective in polycarbonate formation. The highest activity, albeit lower than that of the previously reported Ti catalysts based on saturated NHC, was obtained with the benzannulated NHC-Ti catalyst. Attempts to synthesize unsaturated and benzannulated NHC analogues based on Hf invariably led, as in earlier work with Zr, to a mixture of products that include zwitterionic and homoleptic complexes. However, the benzannulated NHC-Hf complexes were obtained as the major products, allowing for isolation. Although these complexes selectively form polycarbonate, their catalytic performance is inferior to that of analogues based on saturated NHC.
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Mattoussi, Hedi, Liang Du, Neda Arabzadeh Nosratabad, and Zhicheng Jin. "(Keynote) N-Heterocyclic Carbene-coated Gold Nanoparticles and Luminescent Quantum Dots." ECS Meeting Abstracts MA2022-02, no. 20 (October 9, 2022): 904. http://dx.doi.org/10.1149/ma2022-0220904mtgabs.
Повний текст джерелаАнотація:
N-heterocyclic carbenes (NHCs) have generated much interest for use as versatile metal-coordinating groups, since they were first synthesized by Arduengo and coworkers in 1991. NHC molecules can be considered as L-type ligands, because they share their non-bonding electron pairs with the σ-accepting orbital of transition metals, and this endows them with strong coordination interactions. NHC-appended molecules have recently been actively exploited as potentially effective ligands for the surface passivation of various colloidal nanomaterials. We investigate the coordination interactions between a few representative colloidal nanocrystals, including gold nanoparticles (AuNPs) and luminescent quantum dots (QDs), and a NHC-based polymer ligand. The latter presents multiple NHC groups and several short poly (ethylene glycol) (PEG) chains as solubilizing blocks. We find that our NHC-decorated ligands rapidly coordinate onto both sets of nanocrystals, which we attribute to their soft Lewis base nature. These ideally match the soft Lewis acid character of transition metal colloid surfaces, promoting strong coordination bonding through soft‐soft interaction. We combine NMR spectroscopy, fluorescence spectroscopy, high-resolution transmission electron microscopy supplemented with dynamic light scattering to characterize the nature of the binding interactions. Furthermore, the long-term stability of the NHC-stabilized nanocolloids have been tested after phase transfer to water, a highly challenging chemical venue for such groups, due to the moisture sensitive nature of NHC molecules. Data show that our NHC-polymer-stabilized AuNPs and QDs exhibit long-term colloidal stability in buffer media while preserving their optical and fluorescing properties, with no sign of degradation or aggregation build up for at least one year of storage. We will discuss the ligand design and synthesis, characterization of the polymer-stabilized nanocrystals under various conditions, with a particular focus on the beneficial effects of ligand multi-coordination interactions onto the nanocolloid surfaces.
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Mostafa, Mohamed A. B. "Review Study of Chiral N-Heterocyclic Carbene (NHC) Ligands in Stereoselective Metal-Catalyzed Reduction Reactions." Scientific Journal for Faculty of Science-Sirte University 2, no. 1 (April 17, 2022): 116–25. http://dx.doi.org/10.37375/sjfssu.v2i1.210.
Повний текст джерелаАнотація:
Stereoselective metal-catalyzed reactions using N-heterocyclic carbene (NHC) ligands have shown significant recent advances, due to the ability of NHC ligands as strong σ-donor species to coordinate with a wide variety of transition metals. Therefore, the design of new ligands and the subsequent strategies for their synthesis enables new applications of their metal complexes in catalysis to be investigated. This study focuses on the applications of different classes of Ir-, Pd- , Au- and Rh-NHC ligand complexes as promising catalysts in the asymmetric hydrogenation, hydrosilylation and transfer hydrogenation reactions.
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Chan, Chung Ying, and Peter J. Barnard. "Rhenium complexes of bidentate, bis-bidentate and tridentate N-heterocyclic carbene ligands." Dalton Transactions 44, no. 44 (2015): 19126–40. http://dx.doi.org/10.1039/c5dt03295d.
Повний текст джерелаАнотація:
Rhenium(i) tricarbonyl complexes of a range of bidentate, bis-bidentate and tridentate NHC ligands have been prepared. These NHC ligands are of interest for possible applications in the development of Tc-99m or Re-186/188 radiopharmaceuticals and the stability of two complexes were evaluated in ligand challenge experiments using the metal binding amino acids l-histidine or l-cysteine.
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Tacke, Matthias, Oyinlola Dada, Cillian O'Beirne, Xiangming Zhu, and Helge Müller-Bunz. "The non-isomorphous crystal structures of NHC—Au—Cl and NHC—Au—Br (NHC is 1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene)." Acta Crystallographica Section C Structural Chemistry 72, no. 11 (October 5, 2016): 857–60. http://dx.doi.org/10.1107/s2053229616015205.
Повний текст джерелаАнотація:
Gold monochloride and monobromide can be transformed into monomeric complexes by ligands such as CO, PPh3or Me2S, and such ligand-stabilized gold monochloride compounds have been investigated as catalysts, luminescent materials and anticancer drugs, especially when coordinated to a lipophilic benzyl-substituted N-heterocyclic carbene (NHC) ligand. The triclinic structures of NHC–Au–Cl {chlorido(1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene)gold, [AuCl(C29H24N2)]} and NHC—Au—Br {bromido(1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene)gold, [AuBr(C29H24N2)]}, determined by X-ray crystallography at 100 K, have one and four molecules, respectively, in their asymmetric units. The chloride compound shows an almost linear C—Au—Cl fragment [179.76 (8)°], with an Au—C distance of 1.976 (3) Å and an Au—Cl distance of 2.3013 (6) Å, while the bromide compound shows surprisingly large geometry deviations, from 1.969 (12) to 2.016 (10) Å for the Au—C distance and from 2.4279 (14) to 2.4796 (12) Å for the Au—Br distance, in the four independent molecules.
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Keita, Hamidou. "Supramolecular Immobilization of Adamantyl and Carboxylate Modified N-Heterocyclic Carbene Ligand on Cucurbituril Substrates." Molecules 27, no. 5 (March 3, 2022): 1662. http://dx.doi.org/10.3390/molecules27051662.
Повний текст джерелаАнотація:
Herein, the design, synthesis, supramolecular interactions and structural analysis of a novel bidentate carboxylate chelating N-heterocylic carbene (NHC) ligand is presented. The NHC structure was modified to strategically incorporate adamantyl moiety for the formation of a supramolecular complex with host molecules such as cucurbiturils. The adamantyl modified NHC ligand could potentially be used in recoverable homogeneous catalysts when Immobilized on a solid support via host–guest chemistry. As a versatile precursor, NHC ligand (8) was synthesized and characterized by 1H-NMR, 13C-NMR, FTIR, single crystal x-ray crystallography and elemental analysis. A proof-of-principle non-covalent immobilization of the NHC ligand (8) with a Cucurbit[7]uril (CB7) host was demonstrated using 1H-NMR titration.
Дисертації з теми "NHC Ligand"
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Geraghty, Paul Bythell. "Studies towards the synthesis of fused N-Heterocyclic carbene precursors." Thesis, University of Canterbury. Chemistry, 2013. http://hdl.handle.net/10092/8197.
Повний текст джерелаАнотація:
This thesis describes the preparation of a various NHC ligands with five and six-membered rings, different fused aromatic cores and the subsequent synthetic development of their complexation of with Ag, Ru and Pd. The investigation and preparation of these compunds was with the intention of exploring their chemical and physical properties. The synthesis of the NHC ligands proved to be difficult, but analysis and characterisation of the side products from the reactions helped to establish successful synthetic methodologies. In both the five and six-membered research conducted a common attribute was established of a pyrid-2-yl substituent at the 1 position or both the 1 and 3 positions, thus providing new NHC ligands to investigate.
The organic syntheis of the research focused on two NHC ligand functionalites, five and six membered rings. The six memerbered rings focused on 1H-perimidine as the core unit and the design of both bidentate and tridentate NHC ligands to mimic the structural binding relationship of 2,2’- bipyridine (bpy) and 2,2’:6’2”-terpyridine (tpy) with various metal salts. The synthesis of the bpy analogues was achieved in good overall yields with minimal synthetic challenges. However, the tpy analogue was unable to be realised due to time constraints and problems associated with its synthesis. The five membered NHC ligands synthesised were to investigate the physical effects of systematically increasing the size of its aromatic core. The main focus of the research was on the phenanthrene imidazole NHC ligands. This was investigated due to the minimal research that has been conducted on this core unit and NHC-complexes. Synthesis of the two-bidentate NHC ligands with an imidazole head group and fused phenanthrene backbone were completed, but this was with a picolyl substituent at the 1 position rather than the pyrid-2-yl substituent. This failure to isolate this product was attributed to steric influences. Pyrene-fused-imidazole NHC ligands were also investigated and pyrene offers a NHC core that hasn’t been investigated previously. However, synthesis and isolation of the NHC ligands proved to be difficult and was associated with the poor solubility of the NHC ligands.
The organometallic NHC synthesis was studied extensively with the main focus on establishing appropriate conditions to give a NHC complex. The main metal investigated was ruthenium as subsequent NHC complexes were expected to have potentially interesting properties such as luminescence. The synthesis of a perimidine and phenanthrene NHC ruthenium complexes have not been isolated before, thus giving new NHC complexes. Many different synthetic routes were attempted to synthesise a perimidine NHC ruthenium complex. However, this proved difficult due to associated higher reactivity of the carbene carbon of perimidine with a new side product as a result of this research. The phenanthrene NHC complex synthesis suffered due to time constraints but potential methodology for their synthesis is stated.
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Medici, Fabrizio. "Interactions entre les Spirosilane de Martin et Base de Lewis coordination, frustration et nouveau ligand anionique." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLET029.
Повний текст джерелаАнотація:
Ce travail de thèse est consacré à l’étude de la réactivité du spirosilane de Martin, une molécule présentant des propriétés intéressantes notamment en présence de bases de Lewis, qui a trouvé des applications diverses comme la détection d’ions fluorures. En ce qui nous concerne, nous avons choisi d’étudier l’interaction de ce dérivé du silicium avec des bases de Lewis neutres fortes tels que les Carbènes N-Hétérocycliques (NHC) qui ont été beaucoup utilisés pour stabiliser les espèces de basse valence des éléments du bloc p. Alors que les NHC sont connus pour former avec les chlorosilanes des adduits pentacoordinés stables, aucun exemple avec des silanes non halogénés n’avaient été décrits avant notre étude. Nous avons montré qu’en fonction de l’encombrement stérique des NHC étudiés, ils forment avec le spirosilane de Martin des adduits de Lewis normaux et anormaux stables. Les propriétés « Paires de Lewis Frustrées » (FLP) du spirosilane avec des NHC encombrés ont été examinées ainsi que l’accès à des nouveaux ligands NHC anioniques portant un motif siliconateThis thesis work is focused on the reactivity of Martin’s Spirosilane, a molecule that displays some interesting properties in particular with different Lewis base, founding some interesting application such us fluoride sensor. In our study, we have chosen N-Heterocyclic Carbene (NHC) because they are well known for stabilising low-valence states of p-block elements or for disclosing new reactivities. Besides, NHC are known to form relatively stable adducts with tetravalent halosilanes and also to stabilise silicon(0) species through potassium graphite reductions, but, to the best of our knowledge, no pentacoordinated NHC-adducts with a non-halogenated silane partner has been synthesised to date.The first part of my PhD was focused on the update of Martin’s spirosilane synthesis due to some problem of reproducibility with the known procedure. Once obtained the product, it was begun the investigation of the interaction with different NHC carbene that afforded the corresponding adducts that were fully characterised. The different adducts were then studied as potential Frustrated Lewis Pair and as precursors of anionic-type ligands for the metal's coordination
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Tronnier, Alexander, Ute Heinemeyer, Stefan Metz, Gerhard Wagenblast, Ingo Muenster, and Thomas Strassner. "Heteroleptic platinum(II) NHC complexes with a C^C* cyclometalated ligand – synthesis, structure and photophysics." Royal Society of Chemistry, 2015. https://tud.qucosa.de/id/qucosa%3A36262.
Повний текст джерелаАнотація:
Platinum(II) complexes [(NHC)Pt(L)] with various β-diketonate based auxiliary ligands (L: 3-meacac = 3-methylacetylacetonato, dpm = dipivaloylmethanato, dbm = dibenzoylmethanato, mesacac = dimesitoylmethanato, duratron = bis(2,3,5,6-tetramethylbenzoyl)methanato) and a C^C* cyclometalated N-heterocyclic carbene ligand (NHC: dpbic = 1,3-iphenylbenzo[d]imidazol-2-ylidene, dpnac = 1,3-diphenylnaphtho[2,3-d]imidazol-2-ylidene or bnbic = 1-phenyl-3-benzylbenzo[d]imidazol-2-ylidene) were found to show different aggregation and photophysical properties depending on the auxiliary ligand. Eight complexes were prepared from a silver(I)–NHC intermediate by transmetalation, cyclometalation and subsequent treatment with potassium-tert-butanolate and β-diketone. They were fully characterized by standard techniques including ¹⁹⁵Pt NMR. Five complexes were additionally characterized by 2D NMR spectroscopy (COSY, HSQC, HMBC and NOESY). Solid-state structures of five complexes could be obtained and show the tendency of the square-planar compounds to form pairs with different Pt–Pt distances depending on the bulkiness of the substituents at the auxiliary ligand. The result of the photophysical measurements in amorphous PMMA films reveals quantum yields of up to 85% with an emission maximum in the blue region and comparatively short decay lifetimes (3.6 µs). Density functional theory (DFT/TD-DFT) calculations were performed to elucidate the emission process and revealed a predominant ³ILCT/³MLCT character. Organic light-emitting devices (OLEDs) comprising one of the complexes achieved 12.6% EQE, 11.9 lm W⁻¹ luminous efficacy and 25.2 cd A⁻¹ current efficiency with a blue emission maximum at 300 cd m⁻². The influence of an additional hole-transporter in the emissive layer was investigated and found to improve the device lifetime by a factor of seven.
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Boschetti, Riccardo. "Synthesis of novel N-heterocyclic carbene precursors for new chiral complexes." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16665/.
Повний текст джерелаАнотація:
Lo scopo del seguente lavoro di tesi è la sintesi e lo studio di nuovi leganti chirali N-eterociclici ad anello espanso derivanti dal diacido canforico. Lo sviluppo di nuovi leganti chirali nasce dalla possibilità di utilizzo in catalisi enantioselettiva. Questa tipologia di leganti sono facilmente sintetizzati dal diacido canforico utilizzando diverse vie di sintesi. La via di sintesi utilizzata permette di ottenere facilmente una funzionalizzazione asimmetrica. Il legante è stato studiato nella sintesi di un nuovo complesso chirale di Pd(II) utilizzando diverse condizioni di reazione. Inoltre, sono state studiate numerose vie di sintesi per nuovi leganti utilizzando i precursori dei leganti e due diversi epossidi. The aim of my training period has been the synthesis of new chiral N-heterocyclic carbene precursors starting from camphoric acid. The development of new chiral ligands starts from their possible use in new catalytic systems for enantioselective transformations. These kinds of ligands are easily synthetized from camphoric acid following different strategies. The synthetic pathway used makes simple the asymmetric functionalization. The ligand was employed in the synthesis of a new complex of Pd(II) in different conditions. In addition, numerous synthetic pathways have been investigated for new ligands using their precursors and two different epoxides.
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Srivastava, Ravi. "Design of a bifunctional alkoxy-NHC ligand for assembling tantalum-rhodium heterobimetallic molecular and silica-supported complexes." Thesis, Lyon, 2020. https://n2t.net/ark:/47881/m6rv0n2x.
Повний текст джерелаАнотація:
Les complexes de métaux de transitions hétérobimétalliques “Early-Late“ (ELHB) offrent des perspectives uniques pour les réactions d’activation de petites molécules grâce à la bifonctionnalité des atomes métalliques mis en jeu. Une des stratégies identifiées afin de diriger et de stabiliser ces assemblages hétérobimétalliques “Early-Late” est de tirer parti de ligands pontants bifonctionnels se caractérisant par la présence de deux fonctions coordinnantes distinctes : une fonction dite “dure”, capable de former des liaisons fortes avec des métaux précoces électrophiles ; et une fonction dite “molle”, exhibant une forte affinité pour les métaux tardifs riches en électrons. Dans la plupart des exemples de ligands bifonctionnels reportés dans la littérature à ce jour, le site donneur pour les métaux tardifs est de type phosphine. Les Carbènes N-Hétérocycliques (NHCs) sont devenus un substitut aux ligands phosphines grâce à leur synthèse relativement aisée ainsi qu’à leur propension à former des complexes métalliques stables et robustes comparés aux phosphines. De plus, une gamme étendue de NHCs fonctionnalisés peut être obtenue par l’introduction d’une grande diversité de groupements fonctionnels sur le squelette du NHC. De manière surprenante, très peu de complexes ELHB supportés par des ligands NHC bifonctionnels ont été reportés dans la littérature jusqu’à présent. Par conséquent, l’objectif de ce travail de thèse est de reporter la synthèse de complexes ELHB à base de Tantale-Rhodium comportant des ligands NHC bifonctionnels. Une méthode efficace, extensive, simple et polyvalente d’un ligand NHC asymétrique présentant un bras hydroxyde a été développée. La structure exacte de ce ligand libre a été examinée : les analyses ont relevées que ce ligand adopte une forme neutre carbène-hydroxyde contenant une liaison hydrogène atypique Ccarbène-HO. Cette plateforme moléculaire a été utilisée avec succès pour la synthèse presque inouïe de complexes Ta-NHC, ainsi qu’une série de complexes Rh-NHC monométalliques. Le potentiel de ces dérivés pour la préparation d’assemblages hétérobimétalliques Ta/Rh a été exploré, soit par i) la réaction de protonolyse entre le groupement hydroxyle libre contenu dans le complexe monométallique de rhodium et le groupement alkyle des précurseurs de tantale, ou par ii) l’incorporation de Rh dans le complexe Ta-NHC via une transmétallation du carbène depuis le tantale vers le rhodium. Des résultats mitigés ont été obtenus dans le cas des dérivés de tantale- alkylidènes, probablement dus à la forte réactivité de cette entité chimique. Cependant, des édifices ELHB bien définis, à base de Ta/Rh et supportés par un NHC ont été obtenus dans le cas des dérivés de Tantale-imido ou siloxy-alkyle. Cela valorise l’utilité de ce motif alcoxy-carbène à promouvoir l’assemblage de ces deux métaux via la coordination préférentielle du ligand “mou” carbénique sur le Rh tandis que le groupement coordinant hydroxyle “dur” est sélectif vis-à-vis du tantale. Les informations obtenues à partir de la réactivité en solution avec des silanols moléculaires ont été utilisées pour développer des exemples rares de complexes ELHB tantale-rhodium supportés sur silice. Finalement, en tant que perspective exploratoire d’une réaction potentielle d’intérêt, une étude computationnelle de l’activation de diazote et sa conversion en ammoniac a été réalisée en utilisant le complexe bimétallique homogène. Les premières étapes du cycle catalytique impliquent le transfert d’hydrures depuis le rhodium vers la liaison η2-N2─tantale, ses étapes sont énergétiquement favorables c’est-à-dire que les états de transition ainsi que les minima locaux d’énergie sont en deçà de 30 kcal∙mol-1. Ces travaux ouvrent des perspectives intéressantes pour l’activation de petites molécules par des espèces ELHB. De futurs travaux se concentreront sur la mise en œuvre de l’activation de N2 au laboratoire en utilisant des complexes supportés sur siliceEarly-Late heterobimetallic (ELHB) transition metal complexes offer unique perspectives in small molecules activation reactions due to the bifunctionality of the metal atoms involved. One identified strategy in order to direct and stabilize ELHB assemblies is to take profit of bifunctional bridging ligands featuring two distinct coordination motifs: one hard, able to form strong bonds with electrophilic early metal centers and one soft nucleophilic site featuring a strong affinity for electron rich late metal centers. In most examples of bifunctional ligands reported to date in the literature, the late-metal donor is a phosphine-derived moiety. N-Heterocyclic carbenes (NHCs) have evolved as a substitute to phosphine ligands due to their relatively easy synthesis and ability to form stable and strong metal complexes when compared to phosphines. Moreover, a versatile range of functionalized NHCs could be synthesized by incorporating wide variety of functional groups in the NHC backbone. Surprisingly, very few ELHB complexes supported by bifunctional NHC ligands have been reported to date. Hence, the aim of this PhD work is to report the synthesis of tantalum-rhodium ELHB complexes utilizing the bifunctional NHC ligands. The efficient, scalable, simple and versatile synthesis of a new unsymmetrical hydroxyl-tethered NHC has been developed. The exact structure of the free ligand platform has been investigated in detail: the analyses reveal that this ligand adopts a neutral hydroxyl-carbene form that features an unusual OH-carbene hydrogen-bonding interaction. This ligand platform was successfully used to yield rare examples of Ta-NHC complexes, as well as a series of Rh-NHC monometallic species. The potential of these derivatives for the preparation of Ta/Rh heterobimetallic assemblies was then explored through either i) the protonolysis reaction between the free hydroxyl pendant group in the monometallic Rh complex and the alkyl moiety from tantalum precursors or ii) the incorporation of Rh into Ta-NHC complexes through carbene transmetallation from Ta to Rh. Mitigated results were obtained in the case of tantalum alkylidene derivatives, likely due to the high reactivity of this chemical motif. However, well-defined NHC-based Ta/Rh heterobimetallic entities were obtained in the case of Ta-imido or Ta-siloxy alkyl derivatives. This showcases the utility of this bifunctional alcoxy-carbene motif to promote the assembly of the two metals, due to the preferred coordination of the “soft” carbene ligand moiety to Rh while the “hard” alkoxy ligand group is selective to Ta. The insight obtained from the reactivity in solution with molecular silanols was utilized to develop rare examples of silica-supported tantalum-rhodium ELHB complexes. Finally, as a prospective exploration of a potential reaction of interest; computational study for nitrogen activation to NH3 was carried out using the homogeneous bimetallic complex. The first few steps of the catalytic cycle involve the transfer of hydride from the rhodium center to the tantalum bound ƞ2-N2 and are energetically favorable i.e., the transition states and the local minima energies are below 30 kcal.mol-1. This work opens attractive perspectives for small molecules activation by ELHB species, and future work will focus on the implementation of the N2 activation in laboratory using the silica-supported complexes
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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.
Повний текст джерелаАнотація:
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
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Berro, Patrick. "Exploring Photocatalytic and Electrocatalytic Reduction of CO2 with Re(I) and Zn(II) Complexes and Attempts to Employ a Novel Carbene Ligand to this Endeavor." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/41625.
Повний текст джерелаАнотація:
With the blend of addressing issues of sustainable energy with the environmental worries regarding emission of greenhouse gases, there is a motivation to target the efficient chemical reduction of CO2. Re(I) integrated photosensitizers and catalysts, synthesized from commercially available ligands, are introduced with the selective CO2 reduction of formic acid, making for a unique class of Re(I) catalysts typically selective for CO as a reduction product. Furthermore, synthesized Zn(II) phosphino aminopyridine complexes are structurally and computationally characterized as well as observed to function as unprecedented electrocatalysts for the reduction of CO2 to formic acid and CO. Lastly, with the importance and popularity of N-heterocyclic carbenes (NHCs) as a class of ligands in the field of organometallic catalysis, six-membered perimidine based carbenes are further explored. Synthesis of a chelating pyridyl-perimidine NHC in addition to potential transition metal catalysts are also attempted.
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Meng, Di. "Caffeine-derived-iron catalyzed carbonyl-ene and Diels-Alder reactions and development of an NHC-diol ligand family." Doctoral thesis, Université Laval, 2018. http://hdl.handle.net/20.500.11794/30271.
Повний текст джерелаАнотація:
Cette thèse de doctorat met en évidence l'utilisation de catalyseurs de fer qui présentent de nombreux avantages par rapport aux autres métaux de transition. En effet, le fer est moins coûteux, respectueux de l’environnement et présente des activités catalytiques intéressantes. Du fait de ces caractéristiques, la catalyse au fer a connu un réel essor ces 15 dernières années. Cette thèse présente la réaction de type carbonyl-ène intermoléculaire catalysée par des sels de fer(II) et de fer(III), utiles pour leur rôle d’acides de Lewis, en employant plusieurs alcènes avec le 3,3,3-trifluoropyruvate d'éthyle. Les sels de FeII, notamment FeCl2, Fe(OAc)2, Fe(NTf)2, Fe(ClO4)2·6H2O, Fe(BF4)2·6H2O et Fe(OTf)2, ont été utilisés pour catalyser cette transformation. Un système efficace utilisant le Fe(BF4)2 anhydre a été développé pour catalyser la réaction carbonyl-ène intermoléculaire de multiples alcènes avec le 3,3,3-trifluoropyruvate d’éthyle, et aussi la réaction carbonyl-ène intramoléculaire du (S)-citronellal. Des rendements entre 36-87% en produits-ène, soit des alcools homoallyliques et de produits de cyclisation du citronellal ont été obtenus par l’utilisation de différents alcènes disubstitués. Les carbènes N-hétérocycliques (NHC) sont reconnus comme des ligands prometteurs en catalyse avec des métaux de transition. Trois sels de xanthinium dérivés de la caféine ont été utilisés comme précurseurs NHC pour développer des complexes fer-ligand NHC pour les réactions carbonyl-ène intra- et intermoléculaires. Les conditions optimales ont été étudiées, notamment le choix du sel de fer, du solvant, de la charge catalytique et du contreanion. Fe(OTf)2 est apparu comme le meilleur catalyseur lorsque complexé au ligand NHC dérivé du sel de xanthinium caféine méthylé. Avec [NHC-Fe]2+(SbF6)22− comme catalyseur, des rendements de 22% à 99% en alcools homoallyliques ont été obtenus pour la réaction carbonyl-ène en employant divers énophiles et le trifluoropyruvate d’éthyle. De plus, NHC-FeIIICl2[SbF6] s’est avéré être un catalyseur efficace et sélectif pour la transformation du citronellal en produit désiré, l’isopulégol. L’aspect recyclable du sel de xanthinium dérivé de la caféine lié au Fe(OTf)2 a été évalué dans la réaction de Diels-Alder en employant des solvants verts, comme le diméthyl carbonate. Le catalyseur a pu être recyclé cinq fois et des rendements identiques ont été obtenus. Différents substrats ont été testés dont des composés dicarbonylés bidendates, cétones, aldéhydes et esters. Les ligands NHC alkoxylés ont été développés comme famille émergente de ligands dans les réactions d’addition conjuguées énantiosélectives. Enfin, de nouveaux ligands NHC-diol ont été synthétisés et testés dans la réaction carbonyl-ène. Ces derniers sont prometteurs en catalyse asymétrique et notamment en catalyse utilisant des métaux de transition.Iron has many advantages compared to other transition metals in homogeneous catalysis, such as relatively cheap price, eco-friendly, good catalytic activities. Hence, these features boosted the development of iron catalysis since 15 years ago. In this thesis, various iron salts including FeII and FeIII were examined as Lewis acid catalysts in the intermolecular carbonyl-ene reaction of various alkenes and ethyl 3,3,3-trifluoropyruvate. FeII salts, such as FeCl2, Fe(OAc)2, Fe(NTf)2, Fe(ClO4)·6H2O, Fe(BF4)2·6H2O, Fe(OTf)2, were found to be effective in catalyzing the reaction. An anhydrous Fe(BF4)2 catalytic system was developed for both of an intermolecular carbonyl-ene reaction of various alkenes and ethyl 3,3,3-trifluoropyruvate and an intramolecular carbonyl-ene reaction of (S)-citronellal. The ene-products, i.e. homoallylic alcohols, were afforded in 36-87% yields giving a scope of various with 1,1-disubstituted alkenes and the cyclization of citronellal. N-heterocyclic carbenes (NHC) are recognized as promising ligands in transition metals catalysis. Three caffeine-derived xanthinium salts were used as NHC precursors to transition metals iron for developing an NHC-iron catalyst in the intermolecular carbonyl-ene reaction and the intramolecular carbonyl-ene reaction of citronellal. Optimized conditions were developed from the screening of iron salts, solvents, catalyst loading and counter anions. Fe(OTf)2 was found to efficiently catalyze the reaction while complexed with NHC ligand derived from methylated caffeine xanthinium salt. Caffeine-derived-[NHC-Fe]2+(SbF6)22− catalyzed carbonyl-ene reaction of various enophiles with ethyl trifluoropyruvate afforded 22-99% yields in homoallylic alcohols. NHC-FeCl2[SbF6] was efficiently and selectively used as a catalyst to convert citronellal into the desired isopulegol. Caffeine-derived xanthinium salt was designed with Fe(OTf)2 as a recyclable catalyst for Diels-Alder reaction in dimethyl carbonate used as a green solvent. Several other green solvents were examined to further study the application of green solvents in organic synthesis. The catalyst, derived from a caffeine-derived xanthinium salt and Fe(OTf)2, was recycled up to five times, while maintaining the same level of yields for the Diels-Alder reaction and recyclability. A relative large scope of substrates including bidentate dicarbonyl compounds, ketones, aldehydes, and esters were tested. Alkoxyl-NHC ligands were developed as a rising family of ligands in enantioselective conjugate addition. A series of new NHC-diol ligands were designed and tested in the carbonyl-ene reaction. These newly developed ligands are promising systems in asymmetric catalysis and transition metal catalysis.
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Maaliki, Carine. "Nouveaux ligands phospho-carbonés : synthèse et chimie de coordination." Toulouse 3, 2012. http://thesesups.ups-tlse.fr/1721/.
Повний текст джерелаАнотація:
La thématique de recherche développée au cours de ce doctorat concerne l'élaboration de nouveaux ligands à caractère donneur extrême en vue d'applications en catalyse. La première partie de ces travaux consiste à la synthèse de ligands phosphorés pauvres en électrons, plus particulièrement des imidazoliophosphines qui représentent des phosphines cationiques où la charge positive portée par un noyau imidazolium est conjuguée avec l'atome de phosphore. De ce fait, deux stratégies de synthèse ont été mises en place : (a) modifier les substituants de la partie phosphorée ou (b) introduire une deuxième charge cationique. Ces deux méthodes ont conduit à la préparation de trois types de ligands pauvres : les amidiniophosphonites, les di-amidiniophosphines et les hydroxy-phosphines cationiques. La limite de la coordination de ces nouveaux ligands pauvres en électrons a aussi été mise en évidence en série rhodium (I). A l'opposé, la seconde partie présente la synthèse de ligands riches en électrons de type ylures de phosphonium et plus précisément, des bis-ylures de diphosphonium. La préparation à partir des motifs 1,2- ou 1,3-diphénylphosphinobenzène et la coordination de ces espèces ont été étudiées. De nouveaux ylures de phosphoniums chiraux ont été également envisagés à partir de leurs précurseurs phosphoniums. La troisième partie s'intéresse à la synthèse de ligands hybrides riches-pauvres par leurs extrémités " électroniquement " opposées et présentant les caractéristiques des deux premières catégories de ligands développés. Des ligands bidentes à extrémités mixtes du type NHC - amidiniophosphine ont ainsi été préparés dans l'optique d'applications catalytiques mais aussi photo-physiques (transfert de charge). Ces nouveaux ligands à caractère donneur extrême, pauvres en électrons pour les amidiniophosphines, et riches en électrons pour les ylures de phosphonium, ouvrent ainsi de nouvelles perspectives en catalyseThe project developed during this PhD thesis aims at the elaboration of novel ligands with extreme donor character for applications in catalysis. The first part of this work, reports on the synthesis of electron-poor phosphorus ligands especially imidazoliophosphines. The positive charge of the imidazolium moiety of these ligands is conjugated with the phosphorus atom. Thereby, two synthesis methods were developed; while the first consists on the modification of the substituents at the phosphorus atom, the second aims to introduce an additional cationic charge. Both methods have yielded three types of electron-poor ligands, namely the amidiniophosphonites, the di-amidiniophosphines and the cationic hydroxyphosphines. The limits of the coordination of these ligands have been evidenced by the preparation of a series of rhodium (I) complexes. By marked contrast, the second part of this project, concerns the synthesis of electron-rich phosphonium ylide ligands, more particularly the diphosphonium bis-ylides. These ligands were elaborated from the 1,2- or 1,3-diphenylphosphinobenzene bridge, prior to complexation. Preparation of chiral phosphonium ylides were also considered. Finally, the third part of this work focuses on the elaboration of hybrid "rich-poor" ligands having a carbene (NHC) and an amidiniophosphine coordinating extremities. These hybrid bidente ligands were developed for catalytic but also for photo-physic (charge transfer) applications. These new ligands with extreme donating character, electron-poor for the amidiniophosphines, and electron-rich for phosphonium ylides, open interesting perspectives in catalysis
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Miles, Meredith. "The Great Potential of Redox Active Ligands: Applications in Cancer Research and Redox Active Catalysis." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1546621531283595.
Повний текст джерелаЧастини книг з теми "NHC Ligand"
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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.
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Hofmann, Peter, and Marcel Brill. "NHCP Ligands for Catalysis." In Molecular Catalysts, 207–34. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2014. http://dx.doi.org/10.1002/9783527673278.ch10.
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Ghana, Priyabrata. "Access to the First NHC-Stabilized Disilavinylidene". У Synthesis, Characterization and Reactivity of Ylidyne and μ-Ylido Complexes Supported by Scorpionato Ligands, 179–91. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-02625-7_10.
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Stradiotto, Mark, and Rylan J. Lundgren. "Application of Sterically Demanding Phosphine Ligands in Palladium-Catalyzed Cross-Coupling leading to C(sp2)─E Bond Formation (E = NH2, OH, and F)." In Ligand Design in Metal Chemistry, 104–33. Chichester, UK: John Wiley & Sons, Ltd, 2016. http://dx.doi.org/10.1002/9781118839621.ch5.
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Kato, Tsuyoshi, Eddy Maerten, and Antoine Baceiredo. "Non-NHCs Stable Singlet Carbene Ligands." In Topics in Organometallic Chemistry, 131–47. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-04722-0_5.
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Hahn, F. Ekkehardt. "Complexes with Protic N-Heterocyclic Carbene (NR,NH-NHC) Ligands." In Advances in Organometallic Chemistry and Catalysis, 111–32. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118742952.ch9.
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Frenking, G., S. Dapprich, T. Meisterknecht, and J. Uddin. "Structure and Bonding of M(CO)3(H2O), M(CO)5(NH3), and M(CO)5(PH3) (M = Cr, Mo, W)1." In Metal-Ligand Interactions in Chemistry, Physics and Biology, 73–89. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-011-4245-8_4.
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Slaughter, LeGrande M. "Catalysis with Acyclic Aminocarbene Ligands: Alternatives to NHCs with Distinct Steric and Electronic Properties." In N-Heterocyclic Carbenes, 499–524. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2014. http://dx.doi.org/10.1002/9783527671229.ch16.
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Manning, M., A. S. Kolodziejczyk, A. M. Kolodziejczyk, S. Stoev, W. A. Klis, N. C. Wo, and W. H. Sawyer. "Highly potent and selective Tyr-NH2 9-containing linear V1 antagonists and D-Tyr2-containing linear V2 agonists: Potential radioiodinated ligands for vasopressin receptors." In Peptides 1990, 665–67. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3034-9_276.
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Narayana, Yatheesh, Sandhya N.C., H. E. Dinesh, Sridhar B. Thimmaiah, Kanchugarakoppal S. Rangappa, and Kempegowda Mantelingu. "N-Heterocyclic Carbene Mediated Organocatalysis Reactions." In Carbene. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.100642.
Повний текст джерелаАнотація:
Arduengo et al., isolated the first ‘bottleable’ carbene, the first N-heterocyclic carbene (NHC) 1,3-di(adamantyl)imidazol-2-ylidene resulted to an explosion of experimental and theoretical studies of novel NHCs being synthesized and analyzed have huge practical significance. These compounds emerged as successful ligands for coordinating transition metals, the complexes with NHC show diverse applications in the field of catalysis and organic transformation, NHC as ligand to main group elements and their properties and applications. Here this chapter provides the concise overview of N-heterocycle carbene as an organocatalyst that provides different organic transformation on to a carbonyl group. The majority of the NHC catalyzed reactions are employed in the phenomenon of reversing the electrophilic character of carbonyl carbon to nucleophilic carbon (umpolung activity) on coordination suggests benzoin, Stetter and hydroacylation reactions. Also, non-umpolung activity of bis-electrophile α,β-unsaturated acylazoliums reaction with suitable bis-nucleophiles in the organic synthesis have been studied.
Тези доповідей конференцій з теми "NHC Ligand"
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Franich, Andjela, Ivana Vasić, Snežana Rajković, Aleksandar Arsenijević, Marija Milovanović, Nebojša Arsenijević, Jelena Milovanović, and Marija Živković. "CYTOTOXICITY OF CATIONIC DINUCLEAR PLATINUM(II) COMPLEXES IN AN EXPERIMENTAL MODEL OF MOUSE COLON CANCER." In 1st INTERNATIONAL Conference on Chemo and BioInformatics. Institute for Information Technologies, University of Kragujevac, 2021. http://dx.doi.org/10.46793/iccbi21.293f.
Повний текст джерелаАнотація:
The series of nine dinuclear platinum(II) complexes, [{Pt(L)Cl}2(μ-X)]2+ (where L is two NH3 or bidentantly coordinated diamine ligand – ethylenediamine, en; (±)-1,2-propylenediamine, 1,2-pn; isobutylenediamine, ibn; trans-(±)-1,2-diaminocyclohexane, dach; 1,3-propylenediamine, 1,3-pd; 2,2- dimethyl-1,3-propylenediamine, 2,2-diMe-1,3-pd; (±)-1,3-pentanediamine,1,3-pnd, and X is a bridging pyrazine (pz) or pyridazine (pydz) ligand) have been synthesized and characterized. The antitumor potential of these complexes against CT26 cells were determined by in vitro and in vivo assays. A murine model of heterotopic colon cancer tumor was induced in immunocompetent BALB/c mice for investigating antitumor potential of the Pt(II) complexes in vivo. It was found that complexes Pt1, Pt2 and Pt7 shows significant in vitro cytotoxic activity against mouse colon carcinoma CT26 cells, while all these complexes show moderate apoptotic effect. Complexes Pt1 and Pt7 arrested CT26 cells in G2/M phase of cell cycle, while complexes Pt5 and Pt6 exerted the highest antiproliferative effect which was evaluated by detection of Ki67 expressing cells. Complexes Pt1 and Pt2 performed significant in vivo antitumor effects reducing the growth of primary tumor and the incidence of lung and liver metastases without causing the significant hepato- and nephro- toxicity.
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Balhorn, Monique Cosman, and Rod Balhorn. "Abstract 1171: Therapeutic applications of the selective high affinity ligand SH7139 may extend beyond NHL to many other types of solid tumors." In Proceedings: AACR Annual Meeting 2017; April 1-5, 2017; Washington, DC. American Association for Cancer Research, 2017. http://dx.doi.org/10.1158/1538-7445.am2017-1171.
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Petrović, Biljana. "TRANSITION METAL ION COMPLEXES AS POTENTIAL ANTITUMOR AGENTS." In 1st INTERNATIONAL Conference on Chemo and BioInformatics. Institute for Information Technologies, University of Kragujevac,, 2021. http://dx.doi.org/10.46793/iccbi21.009p.
Повний текст джерелаАнотація:
Discovery of the antitumor activity of platinum complex, cisplatin, cis-Pt(NH3)2Cl2, and later carboplatin and oxaliplatin, led to the intensive investigation of the potential antitumor activity of the huge number of platinum complexes. Furthermore, it is well-known that platinum complexes express toxicity, numerous side effects and resistance, so the scientists make a lot of efforts to synthetize, beside Pt(II) and Pt(IV), other non-platinum compounds with potential antitumor activity, such as Pd(II), Ru(II/III) and Au(III) complexes. The goal of this study is to summarize the results of the investigation of the interactions between some mononuclear, homo- and hetero-polynuclear Pt(II), Pd(II), Ru(II/III) and Au(III) complexes with different sulfur- and nitrogen-donor biologically relevant nucleophiles. Among mononuclear complexes, the compounds with aromatic terpy (tepyridine) or bpma (bis-(2- pyridylmethyl)amine) and aliphatic dien (diethylentriamine) nitrogen-containing inert ligands were studied. Different homo- and hetero-polynuclear complexes with pz (pyrazine) or 4,4’-bipy (4,4’- bipyridine) as bridging and mostly en (ethylenediamine), bipy (2,2’-bipyridine) and dach (trans-1,2- diaminocyclohexane) as inert ligands were studied as well. The research was focused on the connection between the structure and the mechanisms of interactions with different biomolecules, such as L- cysteine (L-Cys), L-methionine (L-Met), tripeptide glutathione (GSH), guanosine-5’-monophosphate (5’-GMP), DNA and bovine serum albumin (BSA). Some of these complexes were selected for in vitro studies of the cytotoxicity on different tumor cell lines. Observed results contribute a lot as a guidance for the future design and determination of the structure-activity relationship (SAR) of different transition metal ion complexes.
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Huang, Tur-Fu, H. Lukasiewicz, C. J. Holt, and S. Niewiarowski. "CHARACTERIZATION OF FIBRINOGEN RECEPTORS ASSOCIATED WITH GLTCCPROIEIN IIb/IIIa (GPIIb/GPIIIa) COMPLEX BY TRIGRAMIN, A UNIQUE LOW MOLECULAR WEIGHT PEPTIDE PROBE." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643523.
Повний текст джерелаАнотація:
Trigramin (Mr weight 10 kDa), an acidic, cysteine rich peptide purified into homogeneity from Trimeresurus gramineus snake venom contained a single protein chain with EAGE at the NH2 terminal end. It inhibited platelet aggregation induced by various agents without affecting release reaction. It blocked competitively the binding of 125I-fibrincgen to AEP stimulated and chymotrypsin treated platelets (Ki= 2 × 10−8). 125-I trigramin bound to intact and to AEP stimulated platelets in a saturable manner (approx. 16,000 sites per platelet). However, AEP increased 5 fold, the binding affinity of trigramin to platelets (to Kd = 4 × 10−8M) suggesting that AEP is changing the conformation of receptors associated with GPIIb/GPIIIa complex. The binding of trigramin to thran-basthenic platelets was markedly reduced. The binding to normal platelets was significantly inhibited by EDTA and by monoclonal antibodies directed against GPIIb/GPIIIa complex but not by the antibodies directed against GPIIb or GPIIIa molecules. The binding of 125I-trigramin to AEP-stimulated platelets was inhibited by RGES (IC50 = 125 μM) and by YHHLGGAKOAGDV (C-terminal fragment of fibrinogen gamma chain, IC50 = 250 μM) suggesting that these or similar peptide sequences are required for interactions of various ligands with GPIIb/GPIIIa complex
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Nascimento, Diogo Monteiro do, Moisés Euclides da Silva Júnior, José Endreo Baracho da Costa, Itamar Rodrigues de Lira, and Oscar Olimpio de Araújo Filho. "FABRICAÇÃO DE COMPÓSITOS DA LIGA ALUMÍNIO AA7075 REFORÇADOS COM CARBONETO DE NIÓBIO (NBC) PROCESSADOS VIA METALURGIA DO PÓ." In 74º Congresso Anual da ABM. São Paulo: Editora Blucher, 2019. http://dx.doi.org/10.5151/2594-5327-33284.
Повний текст джерелаЗвіти організацій з теми "NHC Ligand"
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Pizarro, Rodrigo, Raúl Delgado, Huáscar Eguino, and Carlos Pimenta. Marco conceptual para la clasificación del gasto público en cambio climático en América Latina y el Caribe. Banco Interamericano de Desarrollo, September 2022. http://dx.doi.org/10.18235/0004449.
Повний текст джерелаАнотація:
Para alinear el gasto público con las estrategias nacionales de cambio climático y con los compromisos de mitigación asumidos en referencia a las contribuciones determinadas a nivel nacional (NDC, por sus siglas en inglés), los países de América Latina y el Caribe (ALC) necesitan identificar periódicamente los gastos presupuestarios relacionados con el clima, sean de incidencia positiva o negativa. En función del hecho de que todavía no existe una metodología consensuada a nivel internacional para identificar estos gastos, el objetivo de esta publicación es proponer un marco conceptual y orientaciones metodológicas para los países de ALC, que permitan la identificación, clasificación y evaluación del gasto público verde relacionado con el cambio climático, de forma integrada con los sistemas estadísticos vigentes. La metodología planteada es coherente con el Sistema de Cuentas Ambientales de Naciones Unidas (Naciones Unidas, 2008) y con la clasificación de funciones de gobierno presente en el Marco de Estadísticas de Finanzas Públicas (FMI, 2014), ambos reconocidos estándares estadísticos internacionales. La metodología apunta a usar una matriz de clasificación funcional de doble entrada, que atiende el propósito principal y secundario del gasto ligado al clima, y emplea un enfoque analítico de cuentas satélite. No se trata de un modelo único sino de definiciones metodológicas para que los países construyan sus propios sistemas de clasificación funcional presupuestaria relacionada con el cambio climático, efectúen un seguimiento permanente y sostenible de este tipo de gasto verde, y puedan así evaluar sus resultados e impactos, retroalimentando el proceso de formulación presupuestaria relacionado con el clima.