To see the other types of publications on this topic, follow the link: Heterocyclic structures.
Dissertations / Theses on the topic 'Heterocyclic structures'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Heterocyclic structures.'
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.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Brookman, Charles Alexander. "The molecular structures of some heterocyclic compounds." Thesis, University of Edinburgh, 1993. http://hdl.handle.net/1842/12791.
Full textAbstract:
The gas-phase molecular structures of 2-chloropyridine, 3-chloropyridine, 4-chloropyridine, chloropyrazine, 1,2,3-triazine, 1,3,5-triazine and 1,2,4,5-tetrazine have been determined by electron differaction, and, in the case of the first two and the fourth, by combining them with microwave spectoscopy data. Of particular interest was the combination of ring distortion effects arising from both the chlorine substituent and the nitrogen heteratom. The results tend to indicate a more complicated system than that of purely substituent effects, an area already well documented. One of the interesting facts to emerge from this study is the possible breakdown of this superposition method of predicting distortions when the ring geometry is highly distorted from the hexagonal . When several heteroatoms are present in the ring, especially if they distort in a mutually constructive manner, such high distortions may result. Predictions are then unreliable for determining the extent to which each ring angle is affected. It was also found that the presence of the nitrogen enhances the power of the chlorine to distort the ring, adding further to the evidence that the distortions might not be merely additive.
2
Somphol, Kittiya Chemistry Faculty of Science UNSW. "Synthesis of new heterocyclic structures based on indoles." Awarded by:University of New South Wales. Chemistry, 2007. http://handle.unsw.edu.au/1959.4/40829.
Full textAbstract:
Novel indolo-macrocycles have been generated from the attempts to synthesise bis-indolo-cyclotriveratrylenes by the condensation of I, I'-diindolyl-3,3'-dimethanols catalysed by p-toluenesulfonic acid. The addition of substituents on indoles led to enhanced solubilities of the macrocycles. Nine- and six-membered ring compounds have been synthesized from the acid-catalysed reaction of I,I'-diindolyl compounds and aryl aldehydes. Some reactions of these compounds and the attempted synthesis of 2,2' diindolylmethanes from the cyclic compounds have also been described. The electrophilic substitution reactions of 3-substituted 4,6-dimethoxyindole 2,6-dimethanols and 3-substituted 4,6-dimethoxyindole-7 and 2-carbaldehydes and I-substituted indoles afforded triindolyl dialdehydes. The wriation of substituents at C-7 of indole-7-aldehydes and at C-2 of indole-2-aldehydes has also been discussed. Reaction of the hydroxymethylindole and 1,2-di(indol-I-ylmethyl)benzene gave a new macrocycle. Substitution reactions of 2,2???-diindolylmethane-7,7'-dimethanol and indole-7- and 2-aldehydes gave tetraindolyl dialdehydes. Sodium borohydride reduction of tri- and tetra-indolyl dialdehydes gave tri- and tetra-indolyl dimethanols respectively. Acid-catalysed reactions of tri- and tetra-indolyl dimethanols afforded only calix[3] and [4]indoles respectively when all substituents at C-3 of indoles were aryl groups. New conditions for indole based imine synthesis have been established Macrocyclic imine formation from mono-, di-, tri and tetra-indolyl dialdehydes has been investigated. Reactions of indole-3, 7-dialdehydes and short chain diamines (1,2-diaminoethane, 1,2-diaminobenzene and 1,6-diaminohexane) gave mixtures while the reactions with long chain diamines (1,10 diaminodecane and 1,12-diaminododecane) gave monoindolyl macrocyclic imines. Reaction of indole-2, 7-dialdehydes and short chain diamines afforded diindolyl macrocyclic imines with head-tail structures, and the 2,7';2',2";7",2'''-Tetraindole-7 ,7"'-dialdehyde underwent cyclisation with triindolyl dialdehydes and 1,6-diaminohexane afforded triindolyl macrocyclic imines. 1,2 diaminoethane while the 2,3 ';1',1 ";3 ",2"'-tetraindole-7,7"'-dialdehydes underwent imine, with its precise structure established by X-ray crystallography. Reaction of of 1,3-di(indol-l-ylmethyl)benzene and 1,2 diaminoethane yielded a new macrocyclic reactions with long chain diamines yielded monoindolyl macrocyclic imines. Reaction ring closure with 1,2 diaminoethane and 1,6-diaminohexane.
3
Sprick, Reiner Sebastian. "Polytriarylamines containing fused ring and heterocyclic structures prepared using N-heterocyclic carbene complexes of palladium." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/polytriarylamines-containing-fused-ring-and-heterocyclic-structures-prepared-using-nheterocyclic-carbene-complexes-of-palladium(c09188eb-490b-452c-945a-22979f58c76d).html.
Full textAbstract:
For the preparation of semiconducting polymers often ‘standard’ catalytic systems are used without further optimisation. New ligands, such as N-heterocyclic carbenes have shown excellent activity in cross-coupling reactions (e.g. Suzuki-Miyaura reaction, or Hartwig-Buchwald amination). These systems show excellent conversions under mild conditions and even allow the use of aryl chlorides as reagents. Nevertheless, previously no system has been reported for the synthesis of conjugated polymers, e.g. the Suzuki polycondensation or Buchwald-Hartwig type polycondensation using these catalysts. A NHC-Pd based catalytic system was optimised for a polyamination reaction and the catalyst [(IPr)Pd(allyl)Cl] was found to be the most active. Polytriarylamines were synthesised using the optimised catalytic system and tested in organic field-effect transistors. Mobilities found were low which was found to be attributed to the presence of high molecular weight fractions. Molecular weights were controlled using an in situ end-capping approach and polymers tested in the semiconducting layer of OFETs gave similar mobilities tothose reported earlier. Several polytriarylamines, which have not been reported previously, were synthesised using NHC-chemistry and the in situ end-cappingapproach, as well as polytriarylamines that have been reported previously using Pd/phosphine catalysts. One library containing polymers based on biphenyles andbridged biphenyles and another library containing polymers with bridged oligoarenes were synthesised. Suzuki polycondensation was also studied besides the polyamination protocol and low catalyst loadings and reaction temperatures could be realised using a NHC-Pd catalyst. Sulfur containing monomers that could not be polymerised using the polyamination were polymerised successfully. All polymers were fully characterised and studied as the active layer in organic field-effect transistors. The highest mobilities determined for these polymers (~10-2 cm2/Vs) is close to the highest reported for this class of polymer reported to date.
4
Solinas, Gavino <1984>. "N-Heterocyclic carbene complexes of rhodium: structures, dynamics and catalysis." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5637/.
Full textAbstract:
A series of imidazolium salts of the type [BocNHCH2CH2ImR]X (Boc = t-Bu carbamates; Im = imidazole) (R = Me, X = I, 1a; R = Bn, X = Br, 1b; R = Trityl, X = Cl, 1c) and [BnImR’]X (R’ = Me, X = Br, 1d; R’ = Bn, X = Br, 1e; R’ = Trityl, X = Cl, 1g; R’ = tBu, X = Br, 1h) bearing increasingly bulky substituents were synthetized and characterized. Subsequently, these precursors were employed in the synthesis of silver(I)-N-heterocyclic (NHC) complexes as transmetallating reagents for the preparation of rhodium(I) complexes [RhX(NBD)(NHC)] (NHC = 1-(2-NHBoc-ethyl)-3-R-imidazolin-2-ylidene; X = Cl; R = Me, 4a; R = Bn, 4b; R = Trityl, 4c; X = I, R = Me, 5a; NHC = 1-Bn-3-R’-imidazolin-2-ylidene; X = Cl; R’ = Me, 4d, R’ = Bn, 4e, R’ = Trityl, 4g; R’ = tBu, 4h).
VT NMR studies of these complexes revealed a restricted rotation barriers about the metal-carbene bond. While the rotation barriers calculated for the complexes in which R = Me, Bn (4a,b,d,e and 5a) matched the experimental values, this was not true for the complexes 4c,g, bearing a trityl group for which the values are much smaller than the calculated ones. Energy barriers for 4c,g, derived from a line shape simulation, showed a strong dependence on the temperature while for 4h the rotational energy barrier is stopped at room temperature.
The catalytic activity of the new rhodium compounds was investigated in the hydrosilylation of terminal alkynes and in the addition of phenylboronic acid to benzaldehyde.
The imidazolium salts 1d,e were also employed in the synthesis of new iron(II)-NHC complexes.
Finally, during a six-months stay at the University of York a new ligand derived from Norharman was prepared and employed in palladium-mediated cross-coupling.
5
Zapf, Christoph W. "Novel guanidinylating reagents and heterocyclic structures for peptidomimetic drug design /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2003. http://wwwlib.umi.com/cr/ucsd/fullcit?p3091332.
Full text
6
Oughtred, R. E. "The crystal and molecular structures of some heterocyclic thioamides and related metal complexes." Thesis, University of Newcastle Upon Tyne, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370179.
Full text
7
Brucka, Marta Anna. "N-Heterocyclic carbene complexes of silver, rhodium and iron: structures, dynamics and catalysis." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/3873/.
Full textAbstract:
The research performed in the framework of this Master Thesis has been directly inspired by the recent work of an organometallic research group led by Professor Maria Cristina Cassani on a topic related to the structures, dynamics and catalytic activity of N-heterocyclic carbene-amide rhodium(I) complexes1. A series of [BocNHCH2CH2ImR]X (R = Me, X = I, 1a’; R = Bz, X = Br, 1b’; R = trityl, X = Cl, 1c’) amide-functionalized imidazolium salts bearing increasingly bulky N-alkyl substituents were synthetized and characterized. Subsequently, these organic precursors were employed in the synthesis of silver(I) complexes as intermediate compounds on a way to rhodium(I) complexes [Rh(NBD)X(NHC)] (NHC = 1-(2-NHBoc-ethyl)-3-R-imidazolin-2-ylidene; X = Cl, R = Me (3a’), R = Bz (3b’), R = trityl (3c’); X = I, R = Me (4a’)).
VT NMR studies of these complexes revealed a restricted rotation barriers about the metal-carbene bond. However, while the rotation barriers calculated for the complexes in which R = Me, Bz (3a’,b’ and 4a) matched the experimental values, this was not true in the trityl case 3c’, where the experimental value was very similar to that obtained for compound 3b’ and much smaller with respect to the calculated one. In addition, the energy barrier derived for 3c’ from line shape simulation showed a strong dependence on the temperature, while the barriers measured for 3a’,b’ did not show this effect. In view of these results and in order to establish the reasons for the previously found inconsistency between calculated and experimental thermodynamic data, the first objective of this master thesis was the preparation of a series of rhodium(I) complexes [Rh(NBD)X(NHC)] (NHC = 1-benzyl-3-R-imidazolin-2-ylidene; X = Cl, R = Me, Bz, trityl, tBu), containing the benzyl substituent as a chiral probe, followed by full characterization. The second objective of this work was to investigate the catalytic activity of the new rhodium compounds in the hydrosilylation of terminal alkynes for comparison purposes with the reported complexes.
Another purpose of this work was to employ the prepared N-heterocyclic ligands in the synthesis of iron(II)-NHC complexes.
8
Carvalho, Luísa da Conceição Costa Rainho de. "Development of novel benzimidazole- based COX Inhibitors new synthetic strategies and screening of heterocyclic structures." Doctoral thesis, Faculdade de Ciencias e Tecnologia, 2014. http://hdl.handle.net/10362/13142.
Full text
9
Resch, Stefan Günter. "Dinuclear Copper and Nickel Complexes of New Multidentate N-heterocyclic Carbene Ligands: Structures, Dynamics and Reactivity." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://hdl.handle.net/21.11130/00-1735-0000-0005-12D5-6.
Full text
10
Resch, Stefan Günter [Verfasser]. "Dinuclear Copper and Nickel Complexes of New Multidentate N-heterocyclic Carbene Ligands: Structures, Dynamics and Reactivity / Stefan Günter Resch." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2019. http://d-nb.info/1224100247/34.
Full text
11
Tate, Brandon Kyle. "Frontiers in the organometallic chemistry of silver: Accessing new structures and reactivity through sterically demanding, electron-rich N-heterocyclic carbene ligands." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54451.
Full textAbstract:
The synthesis and characterization of novel complexes of silver supported by sterically demanding, highly electrophilic N-heterocyclic carbene (NHC) ancillary ligands, is described. Stable hydride, fluoride, alkoxide, alkyl, aryl, and alkynyl complexes are characterized by NMR spectroscopy and X-ray diffraction crystallography, and their reactivity is investigated. The interaction of silver centers in dinuclear complexes is probed by 109Ag NMR spectroscopy. Relevance to renewable fuel technology is demonstrated through the mediation of fundamental chemical transformations, including the heterolysis of hydrogen, the transfer of hydride to carbon dioxide, and the formation of carbon-carbon bonds. Kinetic studies shed light on the mechanism of hydrogen activation by hard-soft mismatched complexes of silver, and a formal catalytic cycle for the hydrogenation of carbon dioxide to formate derivatives is reported.
12
Wang, Xinjiao [Verfasser], and Karsten [Akademischer Betreuer] Meyer. "Nickel Complexes of N-Heterocyclic Carbene Ligands for Catalytic Application in Pre-Organized and Ordered Structures / Xinjiao Wang. Betreuer: Karsten Meyer." Erlangen : Universitätsbibliothek der Universität Erlangen-Nürnberg, 2012. http://d-nb.info/1023597519/34.
Full text
13
Saxer, Samantha. "Synthèse de structures macromoléculaires aromatiques et hétérocycliques originales par voies non conventionnelles." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI038.
Full textAbstract:
Le travail réalisé dans cette thèse concerne la synthèse de nouvelles structures macromoléculaires aromatiques et hétérocycliques. La synthèse de ces polymères a été envisagée par des procédés de polycondensation non conventionnels. A la différence des réactions classiques utilisées en polycondensation, des réactions de condensation « multi-composants » faisant intervenir trois ou quatre fonctions réactives ont été considérées. Les réactions de Debus-Radziszewski, Hantzsch, et Chichibabin, permettant la formation directe de structures aromatiques et ou hétérocycliques ont été plus particulièrement choisies. Ces polymérisations ont été réalisées à la fois par voie thermique classique et sous irradiation micro-ondes. Trois types de familles de polymères ont été synthétisés avec succès (PIM/PTAI, PPP, P-CNTP). Les résultats obtenus montrent que l’irradiation micro-ondes est bénéfique pour la synthèse de certaines structures, mais cet effet n’est pas systématique. En revanche, la technique d’irradiation sous micro-ondes s’impose comme outil très performant pour le développement de nouvelles structures macromoléculaires de par la réduction significative des temps de polymérisation. L’ensemble de ce travail souligne l’intérêt de la polycondensation par réaction multi-composant et ouvre de nouvelles perspectives pour le développement de nouveaux matériaux polymères aromatiques / hétérocycliquesIn this thesis, the synthesis of new aromatic and heterocyclic macromolecular structures is reported. These polymers have been synthetized by unconventional polycondensation processes. Unlike classic reactions used in polycondensation, "multicomponent" condensation involving three or four reactive functions were here described. More particularly, the reactions of Debus-Radziszewski, Hantzsch, and Chichibabin, allowing the direct formation of aromatic and heterocyclic structures have been chosen. These polymerizations were carried out both by conventional thermal method and under microwave irradiation. Three types of polymer families have been synthesized successfully (PIM / PTAI, PPP, P-CNTP). The results show that microwave irradiation is beneficial for the synthesis of some structures, but this effect is not systematic. On the other hand, microwave irradiation is a powerful tool to develop new macromolecular structures by significantly reducing the time of polymerization. This work underlines the interest of polycondensation by multicomponent reaction and opens perspectives for the development of new aromatic / heterocyclic polymeric materials
14
Oksuz, Nevin. "Quantum-chemical Study Of Geometrical And Electronic Structures Of Aromatic Five-membered Heterocyclic Oligomers In The Ground And Lowest Singlet Excited States." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605397/index.pdf.
Full textAbstract:
The nature of the ground state and the first (lowest) singlet excited state geometrical conformations and electronic transitions in the aromatic five-membered heterocyclic oligomers &ndasholigothiophenes (nT), oligofurans (nF), and oligopyrroles (nP)- containing up to six monomer units (total of 18 molecules) were explored using several computational methodologies. Geometry optimizations were carried out at Austin Model 1 (AM1), Restricted Hartree-Fock (RHF/6-31G*), and Density Functional Theory (DFT, B3LYP/6-31G*) levels for the ground-state conformations of these structurally well-defined heterocyclic oligomers. The Configuration Interaction Singles (CIS) method with the 6-31G* basis set was chosen in computation of the optimal geometry of the lowest singlet excited state. Lowest singlet excitation S1ß
S0 energies were calculated using the Zerner&rsquo
s Intermediate Neglect of Differential Overlap for Spectroscopy (ZINDO/S), CIS (CIS/6-31G*), and Time-Dependent DFT (TDDFT/6-31G* and TDDFT/6-31+G*) methods. In computation of the emission S1à
S0 energies, we have employed all methods above except ZINDO/S. In investigation of geometries of the ground and lowest singlet excited state, we compared the bond length alternation (BLA) parameters, Dri in the conjugated backbone of the oligomers. Saturation of the geometrical parameters at the center of oligomers was observed after a certain chain length. Among all methodologies used in computation of excitation (S1ß
S0) and emission (S1à
S0) energies, TDDFT results showed the best agreement with experimental data. Fits of computed and experimental excitation energies to an exponential function using the least squares method enabled us to predict Effective Conjugation Length (ECL) values. We obtained the ECLs of 17 (17), 16 (15), and 14 (13) monomer units for polythiophene (PTh), polyfuran (PFu), and polypyrrole (PPr), which have very good agreement with the results obtained from the fits of experimental data (the values in parentheses).
15
Nguyen, Thi Ai Nhung, Thi Phuong Loan Huynh, and Van Tat Pham. "Quantum chemical investigation for structures and bonding analysis of molybdenum tetracarbonyl complexes with N-heterocyclic carbene and analogues: helpful information for plant biology research." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-190465.
Full textAbstract:
Quantum chemical calculations at the gradient-corrected (BP86) density-functional calculations with various basis sets (SVP, TZVPP) have been carried out for Mo(CO)4 complexes of Nheterocyclic carbene and analogues-NHEMe (called tetrylenes) with E = C, Si, Ge, Sn, Pb. The equilibrium structures of complexes [Mo(CO)4-NHEMe] (Mo4-NHEMe) exhibit an interesting trend which the lightest adduct Mo4-NHCMe has a trigonal bipyramidal coordination mode where the ligand NHCMe occupies an equatorial position. In contrast, the heavier species from Mo4-NHSiMe to Mo4-NHPbMe possess a square pyramidal structure where the ligands from NHSiMe to NHPbMe occupy a basal position. The slighter complexes Mo4-NHEMe possess end-on-bonded NHEMe ligands when E = C, Si, Ge with the bending angles, α, are 180° whereas the heavier adducts Mo4-NHSnMe and Mo4-NHPbMe exhibit strongly side-on-bonded ligands which the bending angle, α become more acute. The trend of the bond dissociations energies-De [kcal/mol] (BDEs) for the Mo-E bonds is Mo4-NHCMe > Mo4-NHSiMe > Mo4-NHGeMe > Mo4-NHSnMe > Mo4-NHPbMe. Bonding analysis shows that the Mo-E bonds have a significant contribution from (CO)4Mo ← NHEMe π-donation. This is because the energy levels of the π-type donor orbitals of Mo4-NHCMe − Mo4-NHPbMe are higher lying than the σ-type donor orbitals. The NHEMe ligands in Mo4- NHEMe are strong electron donors. This review intends to provide a comprehensive data for plant biology research in the futureTính toán hóa lượng tử sử dụng lý thuyết phiếm hàm mật độ kết hợp điều chỉnh gradient (BP86) từ các bộ hàm cơ sở khác nhau (SVP, TZVPP) được thực hiện cho việc tính toán lý thuyết của phức giữa Mo(CO)4 và phối tử N-heterocyclic carbene và các phức tương tự NHEMe (gọi là tetrylenes) với E = C, Si, Ge, Sn, Pb. Cấu trúc của phức [Mo(CO)4-NHEMe] (Mo4-NHEMe) thể hiện sự khác biệt khá thú vị từ Mo4-NHCMe đến Mo4-NHPbMe, phức Mo4-NHCMe có cấu trúc phối trí lưỡng tháp tam giác trong đó phối tử NHCMe chiếm ở vị trí xích đạo. Ngược lại, những phức có phân tử khối lớn hơn từ Mo4-NHSiMe đến Mo4-NHPbMe lại có cấu trúc tháp vuông và các phối tử từ NHSiMe đến NHPbMe chiếm vị trí cạnh (basal – cạnh hướng về bốn đỉnh của đáy vuông). Các cấu trúc của phức Mo4-NHEMe cho thấy các phối tử NHEMe với E = C-Ge tạo với phân tử Mo(CO)4 một góc thẳng α =180.0°, ngược lại, các phức nặng hơn Mo4-NHEMe thì phối tử NHEMe với E = Sn, Pb liên kết với phân tử Mo(CO)4 tạo góc cong và góc cong, α, càng trở nên nhọn hơn khi nguyên tử khối của E càng lớn. Năng lượng phân ly liên kết của liên kết Mo- E giảm dần: Mo4-NHCMe > Mo4-NHSiMe > Mo4-NHGeMe > Mo4-NHSnMe > Mo4-NHPbMe. Phân tích liên kết Mo-E cho thấy có sự đóng góp đáng kể của sự cho liên kết π (CO)4Mo ← NHEMe. Điều này có thể do mức năng lượng của orbital π-cho của Mo4-NHCMe − Mo4-NHPbMe nằm cao hơn orbital σ-cho. Từ kết quả tính toán có thể kết luận rằng phối tử NHEMe trong phức Mo4- NHEMe là chất cho điện tử mạnh. Kết quả nghiên cứu lý thuyết về hệ phức Mo4-NHEMe lần đầu tiên cung cấp một cơ sở dữ liệu hoàn chỉnh cho các nghiên cứu về sinh học thực vật trong tương lai
16
Nguyen, Thi Ai Nhung, Thi Phuong Loan Huynh, and Van Tat Pham. "Quantum chemical investigation for structures and bonding analysis of molybdenum tetracarbonyl complexes with N-heterocyclic carbene and analogues: helpful information for plant biology research: Research article." Technische Universität Dresden, 2014. https://tud.qucosa.de/id/qucosa%3A29085.
Full textAbstract:
Quantum chemical calculations at the gradient-corrected (BP86) density-functional calculations with various basis sets (SVP, TZVPP) have been carried out for Mo(CO)4 complexes of Nheterocyclic carbene and analogues-NHEMe (called tetrylenes) with E = C, Si, Ge, Sn, Pb. The equilibrium structures of complexes [Mo(CO)4-NHEMe] (Mo4-NHEMe) exhibit an interesting trend which the lightest adduct Mo4-NHCMe has a trigonal bipyramidal coordination mode where the ligand NHCMe occupies an equatorial position. In contrast, the heavier species from Mo4-NHSiMe to Mo4-NHPbMe possess a square pyramidal structure where the ligands from NHSiMe to NHPbMe occupy a basal position. The slighter complexes Mo4-NHEMe possess end-on-bonded NHEMe ligands when E = C, Si, Ge with the bending angles, α, are 180° whereas the heavier adducts Mo4-NHSnMe and Mo4-NHPbMe exhibit strongly side-on-bonded ligands which the bending angle, α become more acute. The trend of the bond dissociations energies-De [kcal/mol] (BDEs) for the Mo-E bonds is Mo4-NHCMe > Mo4-NHSiMe > Mo4-NHGeMe > Mo4-NHSnMe > Mo4-NHPbMe. Bonding analysis shows that the Mo-E bonds have a significant contribution from (CO)4Mo ← NHEMe π-donation. This is because the energy levels of the π-type donor orbitals of Mo4-NHCMe − Mo4-NHPbMe are higher lying than the σ-type donor orbitals. The NHEMe ligands in Mo4- NHEMe are strong electron donors. This review intends to provide a comprehensive data for plant biology research in the future.Tính toán hóa lượng tử sử dụng lý thuyết phiếm hàm mật độ kết hợp điều chỉnh gradient (BP86) từ các bộ hàm cơ sở khác nhau (SVP, TZVPP) được thực hiện cho việc tính toán lý thuyết của phức giữa Mo(CO)4 và phối tử N-heterocyclic carbene và các phức tương tự NHEMe (gọi là tetrylenes) với E = C, Si, Ge, Sn, Pb. Cấu trúc của phức [Mo(CO)4-NHEMe] (Mo4-NHEMe) thể hiện sự khác biệt khá thú vị từ Mo4-NHCMe đến Mo4-NHPbMe, phức Mo4-NHCMe có cấu trúc phối trí lưỡng tháp tam giác trong đó phối tử NHCMe chiếm ở vị trí xích đạo. Ngược lại, những phức có phân tử khối lớn hơn từ Mo4-NHSiMe đến Mo4-NHPbMe lại có cấu trúc tháp vuông và các phối tử từ NHSiMe đến NHPbMe chiếm vị trí cạnh (basal – cạnh hướng về bốn đỉnh của đáy vuông). Các cấu trúc của phức Mo4-NHEMe cho thấy các phối tử NHEMe với E = C-Ge tạo với phân tử Mo(CO)4 một góc thẳng α =180.0°, ngược lại, các phức nặng hơn Mo4-NHEMe thì phối tử NHEMe với E = Sn, Pb liên kết với phân tử Mo(CO)4 tạo góc cong và góc cong, α, càng trở nên nhọn hơn khi nguyên tử khối của E càng lớn. Năng lượng phân ly liên kết của liên kết Mo- E giảm dần: Mo4-NHCMe > Mo4-NHSiMe > Mo4-NHGeMe > Mo4-NHSnMe > Mo4-NHPbMe. Phân tích liên kết Mo-E cho thấy có sự đóng góp đáng kể của sự cho liên kết π (CO)4Mo ← NHEMe. Điều này có thể do mức năng lượng của orbital π-cho của Mo4-NHCMe − Mo4-NHPbMe nằm cao hơn orbital σ-cho. Từ kết quả tính toán có thể kết luận rằng phối tử NHEMe trong phức Mo4- NHEMe là chất cho điện tử mạnh. Kết quả nghiên cứu lý thuyết về hệ phức Mo4-NHEMe lần đầu tiên cung cấp một cơ sở dữ liệu hoàn chỉnh cho các nghiên cứu về sinh học thực vật trong tương lai.
17
Beji, Mohamed. "Heterocumulenes alpha -sulfonyles et leurs applications a la synthese de nouvelles structures heterocycliques : alkylation des esters sulfamiques en catalyse par transfert de phase." Paris 7, 1987. http://www.theses.fr/1987PA077183.
Full text
18
Mihaliak, Alicia M. "Clinically Relevant Doses of Chemotherapy Drugs Selectively and Reversibly Block Glioblastoma Neurosphere Proliferation in vitro: A Dissertation." eScholarship@UMMS, 2010. https://escholarship.umassmed.edu/gsbs_diss/492.
Full textAbstract:
My thesis research began with a project in which we were trying to determine the function of embryonic stem cell (ESC)-specific miRNAs. Using luciferase constructs containing miRNA binding sites, luciferase expression was inhibited by endogenous miRNAs in ESCs, and by exogenous miRNAs in HeLa cells. Inhibition of luciferase expression by miRNAs was inhibited in HeLa cells using 2’O-methyl-oligonucleotides. In ESCs, 2’O-methyl-oligonucleotides were only effective in partially inhibiting miR290 function. Partial inhibition of miR290 did not result in any obvious phenotypic changes in mESCs. Later studies using 2’O-methyl-oligonucleotides in ESCs were also unsuccessful. The function of ESC-specific miRNAs has since been studied by re-introducing miRNAs into Dicer -/- cells which cannot make miRNAs. These studies have shown that ESC-specific miRNAs are involved in de novo DNA methylation, self-renewal, and cell-cycle regulation.
Newly diagnosed glioblastoma (GBM) patients rarely survive more than two years even after surgery, radiotherapy, and chemotherapy using temozolomide (TMZ) or 1,3-bis(2-chloroethy)-1-nitrosourea (BCNU). Eventual regrowth of the tumor indicates that some tumor cells are resistant to therapy. GBM neurosphere-initiating cells (NICs) are thought to be similar to tumor-initiating cells in vivo, and will form invasive tumors in mice, making neurosphere cultures a good model system for studying GBMs. To test whether GBM NICs were resistant to chemotherapy, we used a neurosphere formation assay to measure the number of proliferating NICs in the presence of TMZ or BCNU.
The concentrations of chemotherapy drugs required to inhibit neurosphere formation were much less than those required to inhibit bulk cell proliferation or to induce cell death in our neurosphere cultures. For some cultures, there was a robust recovery of neurosphere formation after chemotherapy treatment which appeared to be DNA damage independent. Some of the cultures that showed significant recovery of neurosphere formation underwent reversible cell cycle arrest, possibly reducing chemotoxicity in these cultures. Collectively, these results indicate that GBM neurosphere cultures can regrow after being treated with clinically relevant doses of chemotherapy drugs. Chemotherapy-treated neurosphere cultures remained viable, and formed tumors when injected into mice. Our experiments show that these in vitro assays may be useful in predicting in vivo responses to chemotherapeutic agents.
19
Wyss, Chelsea Marie. "Synthesis, structure and reactivity studies of dinuclear group 11 N-heterocyclic carbene complexes." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54331.
Full textAbstract:
This thesis describes the synthesis, structure and reactivity of singly bridged dinuclear Group 11 metal complexes, supported by N-heterocyclic carbene (NHC) ligands. These complexes include dinuclear copper(I) complexes that demonstrate three-center, two-electron bonding with short intermetallic distances. In the first part of this study, a hydride-bridged dicopper cation, {[(IDipp)Cu]2(μ-H)}+ BF4–, which adopts a bent arrangement about the hydride was isolated. It undergoes facile methanolysis, readily reacts with carbon dioxide to afford a (κ2-formate)-bridged dicopper species, and coordinates carbon monoxide reversibly to form a carbonyl adduct. The [(LCu)2H]+ cation also inserts phenylacetylene to afford a gem-dicopper vinyl cation, a rare example of the insertion of carbon-carbon multiple bonds into a copper hydride.
The second part of this thesis describes the synthesis and structural characterization of the first boryl-bridged dicopper cation {[(SIDipp)Cu]2(μ-B(O2C6H4)}+ BF4–. The solid state structure shows a bent arrangement about the boryl with a short intermetallic distance of 2.4082(2) Å. The boryl-bridged dicopper cation deprotonates phenylacetylene to form a phenylacetylide dicopper complex. It also readily reacts with methanol to form the hydride-bridged dicopper cation. Density functional theory (DFT) calculations were applied to give further insight into the nature of the metal–boron bonds in comparison to the mononuclear analogue. The two electrons contributed by the bridging boryl are shared between the boron and the two copper centers in the [(LCu)2B]+ core. This three-center, two-electron bonding orbital is lower-lying in energy in comparison to the Cu−B σ-bonding molecular orbital in the mononuclear analogue, consistent with a less nucleophilic Cu–B bond.
The NHC ligand also stabilizes an isoleptic series of dinuclear μ-fluoro cations of copper(I), silver(I), and gold(I). In these complexes, a single fluoride acts as the sole bridging ligand between the two group 11 metal centers of the form [(LM)2(μ-F)]+. All three cations are highly sensitive to adventitious moisture, readily forming the hydroxide-bridged dinuclear cations. The gold(I) complex is the most reactive. It activates the C-Cl bonds of CD2Cl2 and adds rapidly across an allene C=C bond to form an allylic C–F bond, and a vinyl anion bound asymmetrically to the two gold(I) centers.
20
Hirsch, Monica Pauline. "Synthesis, structures and reactions of cyanuric-sulfanuric heterocycles." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0018/MQ48011.pdf.
Full text
21
Katzsch, Felix. "Neue heterocyclische Gerüstbausteine mit Kation- und Neutralmolekül-affinen Haftgruppen zum Aufbau von porigen Festkörperstrukturen." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2015. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-157879.
Full textAbstract:
Das Ziel dieser Arbeit war die Synthese neuer heterocyclischer Hydroxyl-funktionalisierter Tekton-Moleküle, die über ein sperriges Grundgerüst verfügen und zur Bildung von porösen organischen Netzwerken sowie Koordinationspolymeren befähigt sind. Um die Sperrigkeit der Zielverbindungen und die Koordinationsfähigkeit bezüglich Metallionen zu gewährleisten, wurden durch Anknüpfung der Heterocyclen Pyridin, Thiophen und Benzo[b]thiophen an Spacer-Elemente, bestehend aus Benzen- und Alkin-Einheiten, entsprechende Derivate hergestellt und umfassend charakterisiert. Die synthetisierten Moleküle liefern eine Vielzahl von Einschlussverbindungen mit Neutralmolekülen, die hinsichtlich ihrer Zusammensetzung, Stabilität sowie Struktur untersucht wurden. Weiterhin konnte das Potenzial der Zielverbindungen als Sensormaterial gegenüber Neutralmolekülen in der Gasphase und unter Ausnutzung der Fluoreszenzeigenschaften gegenüber Metallionen in Lösung betrachtet sowie die Eignung als Linker-Moleküle zum Aufbau von Koordinationspolymeren überprüft werden.
22
Engqvist, Robert. "Syntheses of some tri- and tetracyclic heterocycles containing an indole moiety /." Stockholm, 2004. http://diss.kib.ki.se/2004/91-7140-161-X/.
Full text
23
Yahagi, Isao. "Functionalization of polyisobutylene, and, Synthesis and crystal structure of heterocyclic quinoimines." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185212.
Full textAbstract:
Part I. Functionalization of polyisobutylene. Polyisobutylene(PIB), a large-scale commercial polymer, is of potential interest as the component of block copolymers with unique physical properties. Lochmann and Schlosser used super bases, a combination of n-BuLi and KOtBu, to abstract allylic hydrogens from simple olefins to give anions. We applied this super-base chemistry to PIB to introduce new functional groups, such as carboxylic acid, esters, and amino groups, into the polymer. The functionalization of PIB via PIB-Li, formed by reaction with the base, led to complications because the PIB-Li was too reactive and basic. PIB carboxylic acid was obtained by the reaction of PIB heterocuprate with carbon dioxide without any complications. Part II. Synthesis and crystal structure of heterocylic quinoimines. Various heterocyclic quinones which have oxazole rings as their component were synthesized. The transformation to the quinoimines was achieved by the reaction of quinones and triphenylarsinimines which were prepared by the reaction of triphenylarsine oxide and isocyanates. X-Ray analyses of quinoimines showed that the molecules were not planar. The arylimino groups were out of the plane of the molecule. Each quinoimine had an unique crystal structure.
24
Binobaid, Abber A. "N-functionalised expanded-ring N-heterocyclic carbenes : synthesis, structure and catalysis." Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54962/.
Full textAbstract:
The work presented in this thesis is concerned with the synthesis, metal coordination and applications of expanded (6- and 7-membered) N-functionalised heterocyclic carbenes. It is divided into four chapters, which cover the following areas of research. Chapter One includes the historical and literature review of preparations, reactions, and catalysis applications for different-types of NHC, while in Chapter Two, the syntheses characterisation and solid state properties of new 6- and 7-membered NHC salts (with Mes, DIPP, o-MeOPh and o-MeSPh A/-substituents) are discussed. A new method for synthesising saturated NHC salts, using potassium carbonate as a mild base for the deprotonation of the corresponding formamidines reacted with di-electrophiles under aerobic conditions is presented. Chapter Three describes the syntheses characterisation and solid state structure of rhodium and iridium complexes. Expansion of the ring provides carbenes with NCnhcN angle close to the sp2 angle (120 ), which forces the A/-substituents to bend closer to the metal center. Furthermore, the expanded carbenes are found to be more basic than their 5-membered analogues. The wide NCnhcN angles and greater donor abilities of the expanded NHC carbenes mean that their catalytic applications are interesting to study. Chapter Four presents the results of catalytic performance for the 6- and 7-membered NHC rhodium and iridium complexes in olefin hydrogenation reactions with molecular hydrogen. These complexes are also tested as catalysts in the transfer hydrogenation of ketones.
25
Banert, Klaus, Manfred Hagedorn, and Heiko Peisker. "Synthesis of Stable 1H-Azirines Reinvestigated: A Structural Corrigendum." Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-153930.
Full textAbstract:
The isoquinoline-catalyzed synthesis of pretended 1H-azirines from phenacyl bromides and N,N\'-dialkylcarbodiimides was repeated. The products do not possess the structure of antiaromatic 1H-azirines, but simple N-acyl-N,N\'-dialkylureas were formed instead. This structural corrigendum was confirmed by the independent synthesis of the known ureas and comparison of their 1H NMR and 13C NMR spectroscopic data in the case of six compounds. Thus,1H-azirines keep their classification as very short-lived intermediates.
26
Baba, Eduard. "N-Heterocyclic Carbenes of the Late Transition Metals: A Computational and Structural Database Study." Thesis, University of North Texas, 2005. https://digital.library.unt.edu/ark:/67531/metadc4792/.
Full textAbstract:
A computational chemistry analysis combined with a crystallographic database study of the bonding in late transition metal N-heterocyclic carbene (NHC) complexes is reported. The results illustrate a metal-carbon bond for these complexes, approximately 4% shorter than that of a M-C single bond found in metal alkyl complexes. As a consequence of this result, two hypotheses are investigated. The first hypothesis explores the possibility of multiple-bond character in the metal-carbon linkage of the NHC complex, and the second, considers the change in the hybridization of the carbenoid carbon to incorporate more p character. The latter hypothesis is supported by the results. Analysis of these complexes using the natural bond orbital method evinces NHC ligands possessing trans influence.
27
Banert, Klaus. "Acremolin, a stable natural product with an antiaromatic 1H-azirine moiety? A structural reorientation." Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-153824.
Full textAbstract:
Recently, acremolin (4), a novel modified base, was isolated from a marine-derived fungus and claimed to possess a structure with a 1H-azirine moiety. It is shown now that the reported NMR data are not compatible with this antiaromatic heterocycle, which should be an extremely unstable compound. An isomeric, substituted N2,3-ethenoguanine is presented as a plausible alternative structure of acremolin that is consistent with all spectroscopic data. Thus, 1H-azirines keep their classification as very short-lived intermediates.
28
Skepper, Colin K. "Marine-derived heterocycles structural, synthetic and biological investigations /." Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3386482.
Full textAbstract:
Thesis (Ph. D.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed Jan. 12, 2010). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
29
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.
Full textAbstract:
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.
30
Hu, Xile. "Metal complexes of tripodal N-heterocyclic carbene ligands : synthesis, structure, bonding, and reactivity /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3153698.
Full text
31
Tice, Nathan Charles. "THE SYNTHESIS, STRUCTURE, AND REACTIVITY OF SOME ORGANOMETALLIC-FUSED HETEROCYCLES." UKnowledge, 2006. http://uknowledge.uky.edu/gradschool_diss/297.
Full textAbstract:
The synthesis, structure, and reactivity of some organometallic-fusedheterocycles were studied. This work was divided into three parts: first,thiapentalenyl tricarbonyl manganese complexes [Mn(CO)3{??5-SC7H3-1,3-(R)2}]were synthesized employing thiation on diacyl precursors; second, attempts toform the 5,5-fused ring pyrrole analogs to the thiapentalenyl complexes led to theformation of various amine and imine ligands and manganese complexes, but notthe desired ring-closed pyrroles; third, reductive amination on a ferrocenylmonoaldehyde substrate led to the formation of di(N-(ferrocenylmethyl))-Nmethylamineand its cyanoborane and cyanoborohydride analogs.Isolation of the desired thiapentalenyl manganese complexes wasaccomplished by first forming 1,2-diacylcyclopentadienes (fulvenes), convertingto the corresponding thallium salts [Tl{1,2-C5H3(COR)2}] employing thalliumethoxide, transmetallating with [Mn(CO)5Br], and ring closing using either P4S10or Lawesson's Reagent. Ring closure from the diacylmanganese complexes[Mn(CO)3{??5-1,2-C5H3(COR)2}] gave air stable thiapentalenyl complexes inmoderate to good yield and was tolerable to a variety of functional groups (aryl,arylacetyl, t-butyl). In the cases where 1,2-diarylacetyl complexes wereemployed, the isolated products were "quinoidal". While ring closure on thecorresponding diacylrhenium tricarbonyl complexes was not feasible, it wasobserved that these quinoidal thiapentalenyl structures could be formed on aruthenium Cp* moiety using the arylacetyl fulvenes.Various keto-amines or enol-imines could be formed from the 1,2-dibenzoyl fulvene employing primary amines (R = H, Me, OH, OMe). In thepresence of a reducing agent, neither reduction nor ring closure was observedfor any of the cases investigated. Formation of the corresponding manganesetricarbonyl complex for the methyoxyimine case was accomplished by reaction ofthe enol-methoxyimine with thallium ethoxide and then transmetallating with[Mn(CO)5Br]. Reaction of this keto-imine complex with various reducing agentsdid not lead to the desired 5,5-fused ring pyrrole complex but to reduction to thecorresponding alcohol.Diferrocenylmethyl methylamine complexes were obtained by reaction offerrocene monoaldehyde with ferrocenylmethyl methylamine in the presence of amild reducing agent (NaCNBH3). Isolation under anhydrous conditions gave theunexpected cyanoborohydride salt, di(N-(ferrocenylmethyl))-N-methylammoniumcyanoborohydride. Aqueous work-up gave the corresponding free amine.Conversion of the cyanoborohydride salt to the corresponding cyanoborane,di(N-(ferrocenylmethyl))-N-methylammonium–cyanoborane, was accomplishedby refluxing the cyanoborohydride salt in THF.
32
Smith, Allison. "Synthetic and structural studies of selected three membered heterocycles." Thesis, Queen's University Belfast, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239225.
Full text
33
Gauthier, Étienne. "Chiral complexes based on helicenic N-heterocyclic carbenes : synthesis, structure, photophysical and chiroptical properties." Thesis, Rennes 1, 2020. http://www.theses.fr/2020REN1S083.
Full textAbstract:
Dans le cadre de ma thèse, de nouveaux complexes de métaux de transitions (rhénium, iridium, cuivre, or) chiraux possédant des ligands NHC-hélicéniques ont été synthétisés et les propriétés chiroptiques et photophysiques ont été étudiées. Le premier sujet d’étude s’est focalisé sur l’étude de complexes de rhénium(I) cyclométallés par des ligands hélicéniques-NHC de type (N^C:) émettant de la phosphorescence circulairement polarisée. Une influence du design du ligand, des ligands ancillaires et de la géométrie des complexes sur les propriétés chiroptiques et photophysiques a été observée. Le deuxième projet a été consacré à l’étude de nouveaux complexes chiraux d’iridium cyclométallés possédant un ou plusieurs ligands N-[6]helicenyl-benzimidazolylidène. L’attention s’est ensuite portée sur des complexes possédant des ligands monodentes. Ainsi, dans le cadre d’un troisième projet, un complexe de cuivre portant un ligand NHC-hélicénique démontrant des propriétés de fluorescence circulairement polarisée a pu être obtenu avec succès. Enfin, des complexes chiraux d’or coordinés par des ligands hélicéniques-NHC ont été préparés. Pendant ce projet, les propriétés électroniques (sigma-donatrice et pi-acceptrice) d’un carbène hélicénique ont été quantifiéesMy PhD work was dedicated to the synthesis and the study of novel chiral transition metal complexes (rhenium, iridium, copper, gold) bearing NHC-helicenes ligands and to the study of their chiroptical and photophysical properties. The first subject focused on the preparation and the study of CP-phosphorescent complexes of cyclometalated rhenium(I) complexes bearing NHC-helicenic (N^C:) ligands. The influence of the ligand design, ancillary ligands and geometry of the complexes on the chiroptical and photophysical properties has been highlighted. In the second project, we have prepared novel chiral cyclometalated iridium complexes bearing one or multiple N-[6]helicenyl- benzimidazolylidene ligands.Then, the attention has been focused on monodentate complexes. Thus, in the third project, a chiral copper complex bearing a helicenic-NHC ligand which emits circularly polarized fluorescence was successfully obtained. Finally, chiral monodentate helicenic-NHC gold(I) complexes have been prepared. During this project, the electronic properties (sigma-donating et pi-accepting) of a helicenic-NHC were investigated
34
Ng, Fei-yeung, and 吳飛洋. "Structure and properties of self-assembled coordination compounds: homoleptic d10-metal aryl/alkylacetylides, ruthenium n-heterocyclesand picolinates." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B37878566.
Full text
35
Ng, Fei-yeung. "Structure and properties of self-assembled coordination compounds : homoleptic d10-metal aryl/alkylacetylides, ruthenium n-heterocycles and picolinates." View the Table of Contents & Abstract, 2006. http://sunzi.lib.hku.hk/hkuto/record/B36587126.
Full text
36
Byrichetti, Kiranmai. "Synthesis and Structure of a Substituted Pyridazine." TopSCHOLAR®, 2011. http://digitalcommons.wku.edu/theses/1080.
Full textAbstract:
Pyridazines are heterocyclic compounds with an N-N bond in their ring structure. Heterocyclic aromatic compounds are of great interest as a result of their novel properties and commercial applications. Our current research is focused on the potential role of pyridazines in next generation electronic devices that utilize organics as the semiconducting material. The synthesis of 5, 6-fused ring pyridazines beginning from fulvenes (Scheme 1) is described herein. These fused heterocycles will serve as synthetic models and building blocks for potential organic or organometallic conducting polymers.
Our goal was to modify the route of Snyder et al. previously reported for the direct synthesis of pyridazine 2. This required improved synthesis of fulvene 1 and higher yields of 5. Additionally, a thorough analysis of the x-ray data was obtained to better understand the 3D aspects of this compound (pyridazine 2).This route was quite general and features an efficient and convenient synthesis.
Single crystal X-ray analysis confirms the molecular structure of pyridazine 2. Full synthesis and characterization of newly formed pyridazine 2 and Fulvene 1 are reported.
37
Boyle, Rosemary. "Synthesis, structure and stereochemistry of metabolites from benzo-fused oxygen heterocycles." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333789.
Full text
38
GIORGI, HERVE. "Analyse des relations structure-activite par modelisation moleculaire et etude des proprietes immunomodulatrices de trois series de composes heterocycliques (doctorat : sciences de la vie et de la sante)." Besançon, 1999. http://www.theses.fr/1999BESA3701.
Full text
39
Bacciu, Deborha. "Abnormally bound n-heterocyclic carbene ligands at group 10 metal centres : synthesis, structure, reaction chemistry and catalysis." Thesis, Cardiff University, 2007. http://orca.cf.ac.uk/56183/.
Full textAbstract:
This thesis describes the synthesis of NHC ligands bound to the C4 or C5 atom of imidazolium ring at Pt and Ni metal centres and the study of their reaction chemistry and catalytic behaviour. In order to prevent deprotonation of the C2-position novel C2-blocked imidazolium salts have been synthesised and their behaviour towards C4.5-H oxidative addition to Pt complexes was investigated. New Pt and Ni hydride complexes bearing NHC ligands coordinated at the C4- or Cs-position were isolated and characterised. This work demonstrates that blocking the C2-position of imidazolium salts with alkyl groups does not necessarily prevent such salts interacting with low valent metals, which has implications for catalysis in imidazolium-based ionic liquid solvents. It was also shown that in the presence of alkene, oxidative addition products such as PtHBr(IMes)(1,2-dimethyl-3-propyl-imidazolin-5-ylidene) are susceptible to reductive elimination reactions to give back Pt(IMes)(alkene)2 complexes and C2- blocked imidazolium salts. Novel C2-blocked picolyl-functionalised imidazolium salts 1,2-dimethyl-3-(2-picolyl)imidazolium tetrafluoroborate and 1,3-di(2-picolyl)-2-methylimidazolium iodide were synthesised. Oxidative addition reaction of these salts to Pt afforded Pt(H)(IMes)(1,2-dimethyl-3-(2-picolyl)-2-methylimidazolin-5-ylidene) tetrafluoroborate and Pt(H)(IMes)(1,3-di(2-picolyl)-2-methylimidazolin-5-ylidene) iodide, respectively, with C4-bound abnormal carbene with chelated pyridyl groups isolated exclusively. The picolyl functionalised abnormal NHC Pt-H complexes are not prone to reductive elimination reactions of either the normal or abnormal carbene in presence of alkenes. Picolyl and aminoethyl functionalised blocked and unblocked imidazolium salts were employed in the hydrosilylation of styrene with triethylsilane by in situ generated Pt -catalyst, giving different product selectivity. When using the C2-blocked imidazolium salt the major product was found to be the dehydrogenative product triethyl-styryl-silane, while using the C2-H imidazolium salt the major product was the tftt-Markovnikov triethyl-(l-phenyl-ethyl)-silane. Several ultimately unsuccessful strategies to isolate a C4 free carbene are described. C2-Blocked 1,3-dimesityl-2-methylimidazolium chloride was synthesised but deprotonation of the C4-H position failed, with the C2-Me group deprotonated instead. It seemed necessary designing an imidazolium salt immune to deprotonation at the C2-position and it is also possible that blocking the C5 position with a o-donating alkyl bulky group will protect or stabilise the desired carbenic center.
40
Clement, Nicolas David Stephane. "Zero valent n-heterocyclic carbene complexes of nickel, palladium and platinum : synthesis, structure, reaction chemistry and catalysis." Thesis, Cardiff University, 2005. http://orca.cf.ac.uk/55984/.
Full textAbstract:
This thesis describes the synthesis of coordinatively unsaturated bis- and mono-N-heterocyclic carbenes of Group 10 metal(0) complexes (Ni, Pd, Pt) and the study of their reaction chemistry and catalytic behaviour. Novel coordinatively unsaturated mono-NHC-Pd0 (NHC = N-heterocyclic carbene) complexes stabilised with activated olefin ligands (dimethylfumarate, DMFU and p-benzoquinone, BQ) have been synthesised and characterised, including by X-ray crystallography. The Pd (NHC)(DMFU)2 complexes were found to be the thermodynamic products of an equilibrium between bis- and mono-NHC-Pd (DMFU) species, the equilibrium reaction driven by the formation of an NHC-DMFU coupling product. The Pt (NHC)(DMFU)2 complex was also synthesised. Novel coordinatively unsaturated bis- and mono-NHC-Ni complexes stabilised with DMFU ligands were synthesised and crystallographically characterised. These Ni complexes have a dynamic behaviour in solution, and the same equilibrium observed for palladium between bis- and mono-NHC-M (DMFU) species with formation of an NHC-DMFU coupling product was also demonstrated to occur with nickel. Possible mechanisms for this unusual NHC-DMFU coupling process at these nickel and palladium(O) centres are discussed. The coordinatively unsaturated mono-NHC-Pd (DMFU/BQ) complexes, as well a bis-NHC-Pd complex, were tested as precatalysts in the telomerization of butadiene with methanol. All of these well-defined complexes were found to be extremely active and selective catalysts in the telomerization reaction. The C-H oxidative addition of imidazolium salts/ionic liquids to a coordinatively unsaturated mono-NHC-Pt0 complex and bis-NHC-Ni /Pd complexes was studied. These oxidative addition processes occur quickly under mild conditions and produce the corresponding bis- or tris-NHC-Mn-H complexes as surprisingly stable compounds. X-Ray crystallographic studies of the two tris-NHC-Mn-hydrido complexes (M= Ni, Pd) with the hydride ligands located are reported The combination of the imidazolium C2-H oxidative addition and the NHC-hydrocarbyl reductive elimination processes into a catalytic cycle to form a unique Ni-catalysed imidazo lium-alkene coupling reaction is reported. The scope of this new catalytic transformation that produces 2-alkylimidazolium salts under mild conditions is extended to other types of azolium salts. The implications of these results for NHC chemistry and for the use of imidazo Hum-based ionic liquids as solvents in transition-metal catalysed reactions is discussed.
41
McConnell, Cameron Reed. "Leveraging 1,2-Azaborine's Distinct Electronic Structure to Access New Building Blocks:." Thesis, Boston College, 2019. http://hdl.handle.net/2345/bc-ir:108607.
Full textAbstract:
Thesis advisor: Shih-Yuan LiuDescribed herein are three projects that derive from in-depth studies of the distinct electronic structure of monocyclic 1,2-dihydro-1,2-azaborine (heretofore referred to as simply 1,2-azaborine). In the first chapter, the first comprehensive review of the late-stage functionalization methods available for 1,2-azaborines as well as their bicyclic and polycyclic (BN-PAH) counterparts is presented. In the second chapter, the development of a general method for both C4 and C5 functionalization based on the building block approach is described. The distinct electronic structure of 1,2-azaborine enables the chemical separation and further functionalization of C4 and C5 borylated isomers. In the second part, the C4, C5, and C6 isomers of BN-styrene analogues were prepared using the newly developed azaborine building blocks. The corresponding polymers were synthesized and extensively characterized in order to compare the effects of the BN-bond positioning relative to the polymer chain. In the fourth and final chapter, 1,2-azaborine-containing phosphine ligands featuring a P-B bond are synthesized. A comparative electronic structure analysis is performed between the BN-phosphine ligands and their direct all-carbon counterparts
Thesis (PhD) — Boston College, 2019
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry
42
Martens, Thierry. "Comportement physico-chimique de dithiolel, 2 thiones-3 : relation structure- activite antibilharzienne." Paris 6, 1988. http://www.theses.fr/1988PA066397.
Full textAbstract:
La reduction electrochimique de (pyradinyl-2)-5- ou (pyridyl-2)-5 methyl-4 dithiole-1,2 thiones-3 est etudiee; elle conduit a des pyrrolo (1,2-a) pyrazines, ou des indolizines respectivement. Des hypotheses sont proposees pour expliquer l'activite anthelminthique des composes du titre
43
Matuska, Vit. "Five-membered sulfur-nitrogen ring compounds." Thesis, St Andrews, 2009. http://hdl.handle.net/10023/828.
Full text
44
Banert, Klaus, Manfred Hagedorn, and Heiko Peisker. "Synthesis of Stable 1H-Azirines Reinvestigated: A Structural Corrigendum." Technische Universität Chemnitz, 2012. https://monarch.qucosa.de/id/qucosa%3A20132.
Full textAbstract:
The isoquinoline-catalyzed synthesis of pretended 1H-azirines from phenacyl bromides and N,N\'-dialkylcarbodiimides was repeated. The products do not possess the structure of antiaromatic 1H-azirines, but simple N-acyl-N,N\'-dialkylureas were formed instead. This structural corrigendum was confirmed by the independent synthesis of the known ureas and comparison of their 1H NMR and 13C NMR spectroscopic data in the case of six compounds. Thus,1H-azirines keep their classification as very short-lived intermediates.
45
Asadi, Ali. "DNA-inspired Janus AT and GC heterocycles : synthesis, structural analysis and self-organization." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/7680.
Full textAbstract:
Inspired by the significance of hydrogen bond driven self-organization, especially from
the base-pairing interactions of double helical DNA, this dissertation discusses the synthesis and
characterization of a number of DNA-inspired self-complementary heterocycles and the
supramolecular ensembles derived from them. Specifically, two projects have been completed.
Each of these projects addresses the high yielding syntheses of heterocycles with defined
hydrogen bond accepting and donating capabilities designed to self-assemble under the general
purview of base pairing.
The first chapter provides an introduction to general concepts such as base-pairing as
well as an outline of the diverse synthetic supramolecular ensembles that have been prepared by
utilizing such interactions. Chapter 2 focuses on the syntheses and solid-state structures of three
self-complementary DNA-inspired heterocycles which contain ADA-DAD hydrogen bond
acceptor-donor patterns (Janus AT 1-3). These novel heterocycles represent diaminopurine
thymine hybrids that, in two of the three cases, relate to previously reported heterocyclic hybrids
of guanine and cytosine. All three heterocycles crystallized and afforded the first X-ray crystal
structures of such heterocycles and revealed their extended H-bonded arrays. This chapter also
introduces the synthetic development to build Janus AT deoxynucleosides, capable of being
oligomerized, as the current trend of this project. The potential use of Janus AT heterocycles in
DNA and RNA recognition is briefly discussed as well. Chapter 3 will disclose the synthesis and
characterization of a DNA-inspired self-complementary heterocycle capable of AAD-DAA
hydrogen bond pairing, which self-organizes to a tetrameric rosette, that unlike a G-quartet,needs no metal binding or peripheral component for pre-organization (Janus GC 1). Notably,
ESI-MS, variable temperature ¹H-NMR, 2D-NOESY and DOSY ¹H-NMR have been exploited
to validate the tetrameric stoichiometry in this non-covalent rosette comprising twelve H-bonds.
At the end of each of these chapters, a section pertaining to ongoing efforts and proposed future
research is included.
46
Meyer, Luke. "Structure-Property Relationships of N-Heterocycle Functionalized Triphenylphosphine Oxide-Based Poly (Arylene Ether)s." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright154651093060725.
Full text
47
Zhukhovitskiy, Aleksandr V. (Aleksandr Vadymovich). "Surface chemistry of N-Heterocyclic carbenes and the self-assembly, structure, and properties of polymer metal-organic cage gels." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105052.
Full textAbstract:
Thesis: Ph. D. in Organic Chemistry, Massachusetts Institute of Technology, Department of Chemistry, 2016.Cataloged from PDF version of thesis. Vita.
Includes bibliographical references.
Chapter 1. Introduction to Carbene Ligands in Surface Chemistry: From Stabilization of Discrete Elemental Allotropes to Modification of Nanoscale and Bulk Substrates In this chapter, we review the development of carbene surface chemistry from its inception through 2015, covering elemental allotrope substrates, nanomaterials, and bulk surfaces, as well as persistent and non-persistent carbenes. We synthesize from the reviewed reports a mechanistic understanding of this chemistry and outline the road ahead in this field. Chapter 2. Addressable Carbene Anchors for Gold Surfaces New strategies to access functional monolayers could augment current surface modification methods. Here we present addressable N-heterocyclic carbene (ANHC) anchors for gold surfaces and provide experimental and theoretical characterization of ANHC monolayers. Additionally, we demonstrate grafting of highly fluorinated polymers from surface-bound ANHCs. Chapter 3. Reactions of Persistent Carbenes with Hydrogen-Terminated Silicon Surfaces We report here the use of persistent aminocarbenes to functionalize via Si-H insertion reactions a range of hydrogen-terminated silicon surfaces: from model compounds, to nanoparticles, and planar Si(l 11) wafers. In particular, a cyclic(alkyl)(amino)carbene and an acyclic diaminocarbene underwent Si-H insertion, forming persistent C-Si linkages and thereby installing amine or aminal functionality in proximity to the surface. Our results pave the way for the further development of persistent carbenes as universal ligands for silicon and potentially other non-metallic substrates. Chapter 4. Cycloelimination of Imidazolidin-2-Ylidene N-Heterocyclic Carbenes: Mechanism and Insights into the Synthesis of Stable "NHC-CDI" Amidinates We report the discovery that 1,3-bis(aryl)imidazolidin-2-ylidenes, one of the most widely studied classes of N-heterocyclic carbenes (NHCs), undergo quantitative conversion to zwitterionic "NHC-CDI" amidinates upon heating to 100 °C in solution. The mechanism of this novel NHC decomposition process was studied in detail and enabled the rational synthesis of a new class of bench stable amidinates. Chapter 5. Toward Dynamic and Hierarchically Structured Polymer Gels: An Introduction to Polymer Metal-Organic Cage Gels Key challenges in polymer network/gel chemistry are overviewed. Polymer metal-organic cage gels capable of addressing some of these key challenges are introduced. Chapter 6. Highly Branched and Loop-Rich Gels Via Formation of Metal-Organic Cages Linked by Polymers We report here a new class of gels (called 'polyMOC' gels) assembled from polymeric ligands and metal-organic cages (MOCs) as junctions with M₂L₄ or M₁₂L₂₄ stoichiometries. The latter features increased branch functionality and large shear moduli, but also an abundance of elastically inactive loop defects that allow via ligand exchange the introduction of function at no cost to the gel's mechanical properties.
by Aleksandr V. Zhukhovitskiy.
Ph. D. in Organic Chemistry
48
Hemming, Oliver. "Structure and reactivity of low-coordinate first-row transition metal complexes." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/structure-and-reactivity-of-lowcoordinate-firstrow-transition-metal-complexes(a7879b58-897e-4080-99f6-8551511a503a).html.
Full textAbstract:
Earth-abundant first-row transition metals have seen a renaissance in chemistry in recent years due to their relatively low toxicity and cost in comparison to precious metals. Furthermore open-shell transition metal complexes exhibit useful one-electron redox processes which contrasts to their heavier d block anologues. This thesis aims to synthesize and analyse the structure and reactivity of low-coordiante first-row transition metal complexes of from groups 7-9 with an aim to utilize these species in catalysis. The divalent compound [Co{N(SiMe3)2}2] reacts with the primary phosphines PhPH2 in the presence of an NHC ligand (IMe4) to yield the phosphinidene bridged dimer [(IMe4)2Co(µ-PMes)]2. The complex has interesting magnetic properties due to strong antiferromagnetic coupling between the two cobalt(II) centres. Increasing the steric bulk of the NHC yielded carbene-phosphinidene adducts (NHC·PAr). This transformation was shown to be catalytic. The structure and reactivity of complexes of the type [(NHC)xMn{(N(SiMe3)2}2] were investigated. The complexes exhibit similar structural properties to their iron and cobalt analogues; however their reactivity has been shown to differ. The addition of primary phosphines to complexes of the type [(NHC)xMn{N(SiMe3)2}2] yielded a range of manganese phosphide complexes. [Mn{N(SiMe3)2}2] also reacts with imidazolium salts at elevated temperatures to yield heteroleptic manganese NHC complexes. The reaction of [Mn{N(SiMe3)2}2] with IPr·HCl afforded the abnormal carbene complex [(aIPr)Mn{N(SiMe3)2}µ-Cl]2. A new monoanionic bidentate ligand is reported which has shown to be a useful ligand system to stabilize three-coordiante iron(II) complex. The reaction of [(L)Fe(Br)] with mesitylmagnesium Grignard or n-butyllithium yield the iron hydrocarbyls [(L)Fe(Mes)] and [(L)Fe(nBu)] with the latter being stable to β-hydrogen elimination. Finally [(L)Fe(nBu)] has been utilized as a pre-catalyst in the hydrophosphination of internal alkynes, showing selectivity for the E-isomeric vinylphosphine.
49
Nguyen, Ha Hoang. "Structural Factors that Influence the Inhibition of Type II Restriction Enzymes by Minor Groove Binders." Digital Archive @ GSU, 2009. http://digitalarchive.gsu.edu/chemistry_theses/17.
Full textAbstract:
The objective of this thesis was to study whether heterocyclic dicationic compounds that are minor groove binders have the ability to inhibit the digestive properties of type II restriction enzymes which bind to the major groove of the DNA. If these compounds do possess the ability to inhibit restriction enzymes, then what factors influence their ability to inhibit the restriction enzymes? The methods used to study the interactions of DNA, compounds, and enzymes are gel electrophoresis, DNA thermal melting, and circular dichroism. The results from this project reveal that the minor grove binding compounds are able to inhibition type II restriction enzymes. The inhibition is heavily influenced by compound structure and the DNA binding sequence of the enzyme.
50
Momin, Mohasin [Verfasser], and Michael R. [Akademischer Betreuer] Buchmeiser. "Structure-property insights into molybdenum imido alkylidene N-heterocyclic carbene complexes for olefin metathesis / Mohasin Momin ; Betreuer: Michael R. Buchmeiser." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2021. http://d-nb.info/1233287842/34.
Full text