• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 34
  • 12
  • 7
  • 5
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 79
  • 26
  • 25
  • 23
  • 13
  • 13
  • 12
  • 10
  • 10
  • 9
  • 8
  • 8
  • 8
  • 7
  • 7
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Calixarene supported transition metal clusters

Taylor, Stephanie Merac January 2013 (has links)
This thesis describes a series of calix[n]arene polynuclear transition metal and lanthanide complexes. Calix[4]arenes possess lower-rim polyphenolic pockets that are ideal for the complexation of various transition metal and lanthanide centres. Surprisingly however, with only a few exceptions, the coordination chemistry of p-tBucalix[ 4]arene (TBC[4]), p-tBu-calix[8]arene (TBC[8]) and p-tBuhomotrioxacalix[ 3]arene (TBOC[3]) with paramagnetic transition metal ions for the purpose of making and studying magnetically interesting molecules is unknown. Chapter two describes the reaction of TBC[4] with manganese salts in the presence of an appropriate base (and in some cases co-ligand) resulting in the formation of a family of calixarene-supported [MnIII 2MnII 2] clusters (1-7) that behave as Single-Molecule Magnets (SMMs). These are: [MnIII 2MnII 2(OH)2(TBC[4])2(DMF)6]·2MeOH (1), [MnIII 2MnII 2(OH)2(TBC[4])2(DMF)4(H2O)2]·4MeOH·2DMF (2), [MnIII 2MnII 2(OH)2(TBC[4])2(DMF)6]·2.8MeOH (3), [MnIII 2MnII 2(OH)2(TBC[4])2(DMF)4(EtOH)(H2O)] (4), [MnIII 2MnII 2(OH)2(TBC[4])2(DMSO)6]·2MeOH·2DMSO (5) , [MnIII 2MnII 2(OH)2(TBC[4])2(DMSO)6] (6) and [MnIII 2MnII 2(OH)2(C[4])2(MeOH)6]·4MeOH (7). Variation in the alkyl groups present at the upper-rim of the cone allows for the expression of a degree of control over the self-assembly of these SMM building blocks, whilst retaining the general magnetic properties. The presence of various different ligands around the periphery of the magnetic core has some effect over the extended self-assembly of these SMMs. Chapter three describes how the combination of complementary cluster ligands; sodium phenylphosphinate and the N,O-chelate 2-(hydroxy-methyl)pyridine (hmpH) with TBC[4] results in the formation of two new calixarene-supported clusters. This being an unusual [MnIIIMnII]2 dimer of dimers [MnIIIMnII(O2P(H)Ph)(DMF)2(MeOH)2]2 (8) and a ferromagnetic [Mn5] cage that displays the characteristic bonding modes of each support [MnIII 3MnII 2(OH)2(TBC[4])2(hmp)2(DMF)6](TBC[4]-H)·xDMF ·xH2O (9). Chapter four details how using oxacalix[3]arenes can tune the nature of the metal binding site, by introduction of ≥ 1 ethereal bridge. This results in Mn(II) rather than Mn(III) bonding in the phenolic pocket, and that these components self-assemble with additional Mn(II) and Mn(III) ions to form a [Mn10] supertetrahedron with an unusual oxidation state distribution, [MnII 6MnIII 4O4(TBOC[3])4(Cl)4(DMF)3]∙3.3H2O ∙ 1.5DMF (10). Chapter five introduces a family of lanthanide complexes formed using TBC[8]. Variation in the experimental conditions employed in the reaction of TBC[8] with lanthanide salts (LnX3) provides access to Ln1, Ln2, Ln4, Ln5, Ln6, Ln7 and Ln8 complexes, [Gd(TBC[8]-2H)Cl(DMSO)4]·MeCN·H2O·(DMSO)2·hex (11), [CeIV 4(TBC[8]-6H)2(μ3- O)2(DMF)4]·(DMF)5·hex·MeCN (12), [TbIII 5(TBC[8]-5H)(μ4-O)(μ3- OH)4Cl(DMSO)8(H2O)3]Cl3·(DMSO)2(hex)2 (13), [CeIV 6(TBC[8]-6H)2(μ4-O)2(μ2-OMe)4(μ2- O)2(DMF)4]·(DMF)6·hex (14), [Dy7(TBC[8]-7H)(TBC[8]-6H)(μ4-O)2(μ3-OH)2(μ2- OH)2(DMF)9]·(DMF)3 (15) and [Gd8(TBC[8]-7H)2(μ4-CO3)2(μ5-CO3)2(μ2-HCO2)2(DMF)8] (16), with all polymetallic clusters containing the common bi-nuclear lanthanide fragment. Closer inspection of the structures of the polymetallic clusters reveals that all but one (Ln8) are in fact based on metal octahedra or the building blocks of octahedra.
22

Developing New Ligand Platforms for MRI Contrast Agents

Allen, Kevin John Harvey 08 July 2014 (has links)
A series of lanthanide complexes, {[CpCo(P=O(OR)2)3]2Ln(H2O)x}+Cl- (Ln = Nd, Eu, Tb, Yb; R = Et, Ph), (Kläui)2Ln, were prepared. The related complex {[CpCo(P=O(OPh)2)3]2Yb}+ [CoCl3(THF)]- was crystallographically characterized and the cation in this case was confirmed to be 6-coordinate and solvent free. To determine the Kläui complexes potential as magnetic resonance (MR) imaging agents, ligand exchange rates between the d0- and d60-isotopomers of the Kläui lanthanide complexes were determined in acetonitrile by electrospray mass spectrometry. The ligand exchange rate was found to increase by almost 4-orders of magnitude from the smallest (Yb) to largest ion (Nd) in acetonitrile. Additionally, the ligand exchange rate increased rapidly for the Tb complex with increasing water concentration. Changing the phosphite substituent had no significant impact on the rate of ligand exchange for R = Ph relative to R = Et. Modification to the phosphite substituents to decrease ligand exchange was unsuccessful indicating that these ligands were not suitable as MR imaging agents. Oxazoline based ligands are known to complex lanthanide ions, however, most of these complexes undergo rapid ligand exchange when not in water solution. Several novel oxazoline based ligands with increased chelation to stop ligand exchange were designed. During the course of their synthesis it was discovered that these ligands were too unstable to be used in vivo and this ligand set was abandoned for a more stable alternative. A series of ligands based on a calix[4]arene scaffold were developed. Through modifications to the upper rim of the calix[4]arene scaffold a mono, di, and tri substituted catechol calix[4]arene were designed. After the mono-catechol tri-sulfonated calix[4]arene was found to decompose in solution the catechol substituent was determined to be too reactive for use as a contrast agent. An upper rim tetra substituted iminodiacetic acid calix[4]arene was synthesized. Upon addition of the lanthanide a coordination polymer was likely forming. Using a dye displacement assay it was found that this ligand was not able to out-compete the dye for metal chelation and would not be suitable for MR use. Using established Suzuki chemistry, DO3A functionality was incorporated onto a tri-sulfonated calix[4]arene scaffold. Using a dye displacement assay it was found that the stability constant KML of this complex was similar to DO3A at pH 8.35. At pH 3.99 it was found that no displacement occurred, most likely due to intramolecular hydrogen bonding. / Graduate / 0488 / kjallen@uvic.ca
23

Coordination and H-bonded networks based on thiacalix(4)arene derivatives / Réseaux de coordination et réseaux à base de liaisons hydrogènes à partir d'entités de thiacalix[4]arene

Ovsyannikov, Alexander 03 December 2012 (has links)
Dans ce travail, l’approche de la tectonique moléculaire, basée à la fois sur la reconnaissance moléculaire et le processus itératif d’auto-assemblage à l’état cristallin, a été utilisée pour la formation de réseaux moléculaires de coordination, ainsi que de réseaux moléculaires à base de liaisons hydrogène. La synthèse de nouveaux tectons à base de dérivés de TCA (p-tert-butylthiacalix[4]arene et p-H-thiacalix[4]arene) offrant des groupements coordinants de type pyridine (avec différentes positions de l’azote sur les noyaux pyridiniques) et de dérivés de TMTCA (tetramercaptothiacalix[4]arene) portant aussi des groupement de type pyridine (avec différentes positions de l’azote sur les noyaux pyridiniques) mais aussi cyano, carboxylates, pyrazole et imidazole a été mise au point. Tous les tectons adoptent la conformation 1,3-alternée, permettant l'obtention de réseaux moléculaire de dimensionalité élevée. Les composés obtenus ont été caractérisés à la fois en solution et à l'état cristallin. Leur aptitude à former des réseaux de coordination en présence de métaux de transition (tels que Ag(I), Hg(II), Cd(II), Cu(II), Co(II), Fe(II)) a été explorée. La possibilité de formation de réseaux à base de liaison hydrogènes a été également testée en utilisant le carboxylate-bisamidinium type de reconnaissance. Beaucoup de nouveaux polymères de coordinations possédant diverses dimensionnalités, en particulier, 3D de type diamant, et certaines réseaux à base de liaisons hydrogènes ont été obtenus. La différence de la connectivité entre TCA et TMTCA vis-à-vis des cations métalliques a été étudiée et discutée. / In this work, the molecular tectonic strategy, based on the molecular recognition together with the iterative self-assembly process in the crystalline phase, has been used for the formation of molecular networks (coordination polymer and H-bonded networks). The synthesis of new tectons based on the TCA derivatives (p-tert-butylthiacalix[4]arene et p-H-thiacalix[4]arene) offering pyridyl binding sites with different position of N atom in the rings, as well as the TMTCA derivatives (tetramercaptothiacalix[4]arene) bearing pyridyl (also with different position of N atom in the rings), cyano, carboxylate, pyrazolyl, imidazolyl coordinating groups has been achieved. All tectons were fixed in 1,3-alternate conformation, allowing the formation of high dimensionality networks. The structures of obtained tectons were characterized in solution, as well as in the solid state. The propensity of these tectons to form coordination polymers upon the combination with different transition metal cations such as Ag(I), Hg(II), Cd(II), Cu(II), Co(II), Fe(II) has been expoled. The possibility to form the H-bonded networks has also been investigated using the carboxylate-bisamidinium type of recognition pair. New coordination polymers possessing different dimensionalities (especially 3D diamond like) and some H-bonded networks have been obtained. The differences in the connectivity of TCA and TMTCA towards the metal cations have been studied and discussed.
24

Spatially Directional Resorcin[4]arene Cavitand Glycoconjugates for Organic Catalysis in Aqueous Media

Husain, Ali Husain 27 June 2016 (has links)
Resorcin[4]arenes and their rigid structures “cavitands” offer a unique molecular structure scaffolds suitable for attaching and orienting multi-ligands on their upper rims. Their remarkable structure properties, the relative ease of chemical modification on their either rims or through the multiple phenolic hydroxyl (-OH) groups, manipulating their cavity size and the role of spatial directionality provided by their cores, led synthetic chemist to explore their utilities in the synthesis of valuable resorcin[4]arene/cavitand assemblies with wide range of applications in many research areas such as supramolecular chemistry, host-guest chemistry, glycoconjugates, polymer chemistry, host-guest chemistry, micro-reactors in chemical catalysis and others. In particular, in the field of glycoconjugates, the synthesis of multi-directional glycoresorcin[4]arenes have found valuable uses in glycobiology, i.e. lectins and cells recognitions. Recently, the spatial directionality of β-D-glucopyranoside based on the resorcin[4]arene rigid structure “cavitand” was first described by our group in the synthesis of resorcin[4]arene cavitand glycoconjugates (RCGs). The efficacy of RCGs was established as phase catalysts in order to evaluate their abilities catalyzing different organic transformations in aqueous environment as a green approach in organic syntheses. RCGs showed a variety of advantages such as low catalytic loading and faster conversions for water-insoluble hydrophobic substrates in aqueous media. This dissertation consists of four chapters. Chapter 1 describes the design and the synthesis of a family of spatially directional resorcin[4]arene cavitand glycoconjugates (RCGs) by coupling β-D-glucopyranose moieties on the resorcin[4]arene cavitand upper rims via multiple 1,4-disubstituted 1,2,3-triazolethe linkages achieved from the well-known click reaction, the Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC). The multiple directional β-D-glucopyranoside units on the cavitand cores are capable of multiple H-bond interactions resulting in a significant molecular host system, i.e. “pseudo-saccharide cavity” capable of accommodating different guest molecules, especially hydrophobic organic species, in aqueous environment raising the advantages of these amphiphilies for appreciable applications as molecular vessels and micro-reactors in an ideal atmosphere “water”. In Chapter 2, the utility of RCGs as efficient phase transfer catalysts for thiocyanation and thiazole formation in water is described. The catalytic activity (1 mol% loading) of RCGs enhancing the formation of both thiocyanate and thioazole species in aqueous media is a direct evidence of their capability acting as micro-reactors in water. Also, the recoverability and the reusability of RCGs for thiocyanation and thizaole formation have been examined. Additionally, the influence of the flexibility/rigidity and the orientation of the multiple β-D-glucopyranose moieties on the RCGs’ catalytic efficciency in thiocyanation and thiazole formation has been investigated. In Chapter 3, the design and the synthesis of an octopus-like structure resorcin[4]arene glycoconjugate (RG) is described. RG consists of eight β-D-glucopyranoside units attached to a flexible open system resorcin[4]arene core. The flexibility of the resorcin[4]arene assembly and the presence of the multiple β-D-glucopyranosides provides a wider-type of pseudo-saccharide bucket capable of encapsulating larger molecules in aqueous environment. RG was evaluated for catalyzing the CuAAC in water without the use of any added organic solvent. RG was remarkably efficient in catalyzing the CuAAC reactions in aqueous atmosphere for a variety of small/bulky and hydrophilic/hydrophobic azido and alkyne substrates. In Chapter 4, the construction of resorcin[4]arene cavitand based-carcerands (RCCs) via tandem CuAAC reactions is described. The CuAAC reaction was utilized as an efficient coupling method for the complimentary azido- and alkyne-cavitand halves via multiple 1,4-disubstituted 1,2,3-triazole linkers. Unlike the most reports of covalently linked carcerand synthesis, which are accomplished at very dilute concentration, the fast kinetics of the CuAAC reaction enabled carcerand synthesis at much higher concentration and in high yield.
25

Design, synthesis and evaluation of calix[4]arene based enrichment agents for N-methyl proteomics

Shaurya, Alok 06 January 2021 (has links)
Role of N-methylated lysines (K) and arginines (R) was underappreciated for a long time before the turn of the century. With the help of new emerging technologies, their crucial role in chromatin regulation was established and now their mention when discussing gene regulation is almost a given. Despite this, much about how they contribute to the cellular chemistry is still to be discovered. There is a major gap in current knowledge base due to an incomplete list of possible lysine and arginine methylation sites. This is because of their low copy number inside the cell which makes it difficult to detect them. New methylation sites are being added every day. This thesis aims to provide a solution to this problem by establishing methods that can help detect N-methylated lysines and argnines that are present in really low quantity inside the cell. The work is influenced by a previously established fact that p-sulfonatocalix[4]arene binds methylated lysine over unmethylated ones. We have first attempted to improve this native affinity by decorating the calix[4]arene skeleton with different substituents. To this effect, we have developed methods for regioselective functionalization of calix[4]arene scaffold and then studied their effect on its binding profile against a set of test peptides derived from proteins found in vivo. We then demonstrate a proof-of-concept enrichment method using selected molecules from our inventory. We use these calix[4]arene based molecules as a stationary phase modifier in a chromatography setup and then show that it can separate peptides based on presence of N-methylated lysines and arginines. We propose that introduction of such a method would improve the visibility of low level N-methylated peptides by removing the bulk of back ground unmethylated analytes and thus improving their signal strength. Finally, we establish the utility of this method by showing that more N-methylated lysines are detected from a real-world proteomics sample prepared using our enrichment method. This work opens new avenues for use of supramolecular chemistry in proteomics studies. We believe that this thesis is a confident demonstration that host-guest chemistry can help expand the existing knowledge about bimolecular processes found in vivo and must be explored further. / Graduate / 2021-12-23
26

Survey of the Solid State Conformation of Calix[4]arenes

Obrey, Stephen J. (Stephen James) 08 1900 (has links)
The characteristics of seventy-six calix[4]arene crystal structures derived from the Cambridge Crystallographic Database are presented. This survey is a discussion of the inter and intramolecular effects on the solid state cavity shape and molecular recognition ability of the compounds. In addition to this survey, four new calix[4]arene crystal structures are presented. The conformational characteristics of these four calixarenes are determined by a complicated array of inter and intramolecular interactions in the crystal packing.
27

Expanding the Organometallic Chemistry of 4d and 4f Arene Metal Complexes

Bamforth, Christopher 18 May 2022 (has links)
No description available.
28

Synthesis of the Fluorinated Arylene Alkylene Ether and Research on Its Potential Thermotropic Behavior under Photochemical Crosslink Reaction

Wang, Weiran 09 June 2014 (has links)
No description available.
29

Syntheses and characterization of a t-OCTYLCALIX[5]ARENE derivatized capillary column for gas chromatography

Cripe, M. Kathleen Leslie January 1998 (has links)
No description available.
30

Arene ruthenium dithiolato-carborane complexes for boron neutron capture theory (BNCT)

Romero-Canelón, I., Phoenix, B., Pitto-Barry, Anaïs, Tran, J., Soldevila-Barreda, Joan J., Kirby, N., Green, S., Sadler, P.J., Barry, Nicolas P.E. 18 May 2015 (has links)
Yes / We report the effect of low-energy thermal neutron irradiation on the antiproliferative activities of a highly hydrophobic organometallic arene ruthenium dithiolatoecarborane complex [Ru(p-cymene) (1,2- dicarba-closo-dodecarborane-1,2-dithiolato)] (1), and of its formulation in Pluronic® triblock copolymer P123 coreeshell micelles (RuMs). Complex 1 was highly active, with and without neutron irradiation, towards human ovarian cancer cells (A2780; IC50 0.14 mM and 0.17 mM, respectively) and cisplatinresistant human ovarian cancer cells (A2780cisR; IC50 0.05 and 0.13 mM, respectively). Complex 1 was particularly sensitive to neutron irradiation in A2780cisR cells (2.6 more potent after irradiation compared to non-irradiation). Although less potent, the encapsulated complex 1 as RuMs nanoparticles resulted in higher cellular accumulation (2.5 ), and was sensitive to neutron irradiation in A2780 cells (1.4 more potent upon irradiation compared to non-irradiation). / We thank the Leverhulme Trust (Early Career Fellowship No. ECF-2013-414 to NPEB), the University of Warwick (Grant No. RD14102 to NPEB), the University of Birmingham/EPSRC Follow-on- Fund (Grant No UOBFOF026 to BP), the ERC (Grant No. 247450 to PJS), EPSRC (EP/F034210/1 to PJS).

Page generated in 0.0449 seconds