Thèses sur le sujet « Hydrogen bonding »
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1
Mitchell, John Blayney Owen. « Theoretical studies of hydrogen bonding ». Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358697.
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Mondal, Raju. « Systematic studies of hydrogen bonding ». Thesis, Durham University, 2004. http://etheses.dur.ac.uk/2986/.
Résumé :
This thesis deals with wider application and implications of the hydrogen bond in crystal engineering studies and beyond; in addition, it also highlights the Cambridge Structural Database (CSD) as the potential knowledge-mine for inorganic chemists. The content of this thesis covers mainly three areas, viz, the role of hydrogen bonding in crystal engineering studies, the bridging between mainstream crystal engineering studies and solvates via hydrogen bond, and CSD studies on metal coordination spheres. Chapter 2 deals with crystal structure prediction through understanding the driving forces for forming supramolecular synthons and some rare supramolecular networks (Carbomndum III). With the help of a series of supraminols we attempt to identify the underlying reason for forming P-As networks. Chapter 3 covers the much debated topic of acceptor capabilities of organic halogens and consequently, how the so-called illusory hydrogen bond involving an organic halogen as an acceptor can explain a complex topic like synthon change-over, in a perfectly comprehensible manner. The aim of the Chapters 4 to 6 is to bring two separate fields, "crystal engineering" and "solvates" closer via a common root, like hydrogen bonding. The serendipitous host molecules are part of our crystal engineering studies, yet they form solvates due to less than optimum hydrogen bonding in their respective crystal structures. Alongside some usual solvates, in an unconventional way, different amines with varying steric, strain and donor hydrogen atoms were used. Different geometrical as well as crystallographical aspects and their explicit role in synthon selection has also been discussed. In Chapter 7, geometrical distortions of three-coordinate metal complexes in the crystal structures in the CSD have been analysed using symmetry modified Principal Component Analysis (PCA). Results shows that 90% of three coordinate species are accounted for by the five elements Cu, Ag, Hg, Au and Zn. Among the three major types of geometries, trigonal planar dominates the data sets, with smaller contribution for Y- and T-shaped structure. For Hg complexes, a possible reaction pathway for ligand addition reaction to two-coordinate linear complexes via T-shaped geometries leading to trigonal planar is discussed in detail. The background information and an overview of the experiments are discussed in the Introductory Chapter.
3
Sagar, Rajeeve. « Self-assembly via hydrogen bonding ». Thesis, University of Warwick, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247352.
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Scott, Tianeka S. « Understanding Hydrogen Bonding in Photoenolization ». University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1378196534.
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Howard, Daryl L., et n/a. « Hydrogen bonding in the near infrared ». University of Otago. Department of Chemistry, 2006. http://adt.otago.ac.nz./public/adt-NZDU20060823.150321.
Résumé :
OH-stretching spectra of various vapour phase species were recorded to investigate hydrogen bonding. The species studied include 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, acetylacetone, hexafluoroacetylacetone and the complex formed in the heterogeneous mixture of methanol and trimethylamine. The spectra range from the infrared, near infrared to visible wavelengths. The main focus of this study is in the near infrared region, in which the OH-stretching overtones are dominant.
The near infrared and visible spectrum of formic acid has been recorded to investigate coupling across bonds, specifically a resonance occurring between OH- and CH-stretching vibrations. The same resonance was also observed in the spectrum of 1,2-ethanediol. The spectra of deuterated isotopomers of formic acid and 1,2-ethanediol were recorded to experimentally verify the resonance.
The inherently weak nature of the vibrational overtone transitions required sensitive spectroscopic techniques to observe the spectra. The spectra were recorded with conventional long path length absorption spectroscopy and intracavity laser photoacoustic spectroscopy.
Anharmonic oscillator local mode calculations of the OH-stretching transitions were performed to simulate the observed spectra. These calculations require calculation of potential energy surfaces and dipole moment functions. Simulated spectra obtained with highly correlated ab initio methods and large basis sets have yielded the best agreement with observation.
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Biemond, Gerard Jan Eduard. « Hydrogen bonding in segmented block copolymers ». Enschede : University of Twente, 2006. http://doc.utwente.nl/51102.
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Taylor, Russell Alan. « Hydrogen bonding effects in homogeneous catalysis ». Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500138.
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Thomson, Patrick. « Extremely strong contiguous hydrogen bonding arrays ». Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7856.
Résumé :
When multiple hydrogen bonds lie in-plane and parallel to each other in close proximity, they experience additional positive or negative secondary electrostatic interactions. When a pair of molecules are arranged such that every hydrogen bond acceptor is on one molecule and every hydrogen bond donor is on another, the positive secondary electrostatic interactions are maximised, and thus the association constant of the complex is enhanced. This thesis will present the development of a family of quadruple hydrogen bonded complexes containing only positive secondary interactions, which confers unprecedented stability. The complexes are sufficiently stable to maintain strong binding in polar solvents such as acetonitrile and can be switched “on” and “off” with acid and base. They will be developed into synthons for acid-base responsive supramolecular recognition, for use in stimuli-responsive supramolecular polymers and gelators.
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Locke, Christopher John. « Competitive hydrogen bonding in polymeric systems ». Thesis, University of York, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259805.
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Hayward, Owen David. « Hydrogen bonding in the crystalline state ». Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391181.
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Maskery, James Samuel. « Intramolecular hydrogen bonding in polyhydroxynaphthoquinone dyes ». Thesis, Bangor University, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.664530.
Résumé :
Intra- and inter-molecular hydrogen bonding greatly affects both physical and chemical properties for a wide variety of important molecules. This study focuses on intramolecular hydrogen bonding in polyhydroxy-1 ,4-naphthoquinones. The little known "bond counting rule", dictates that the global minimum will be comprised of a maximum number of highly stabilizing interactions. Hydrogen bonding was chosen for this work as the energy of the bond is typically 20-40 kJ mol-1, which is larger than computational error, allowing statistically significant energy differences between conformers to be determined. A series of interactions between neighbouring hydroxyl groups and each other, and between hydroxyl groups and neighbouring carbonyl groups were postulated. Quantification of the interaction energies was accomplished using a training set of several hundred unique isomers, allowing a quantitative bond counting rule to be developed. Harmonic vibrational spectroscopic and QTAIM analyses were performed for key interactions to aid in their characterisation as baseline, stabilising or destabilising. The effect of molecular conformation upon the wavelength and absorbance of electronic absorption spectra were also probed, highlighting the need to obtain low-energy conformations. Potential energy hypersurface (PES) for single and pairs of C-O bond rotation(s) not only indicate the presence of stationary points corresponding to maxima, minima and transition structures, but also any rotational barriers and reaction pathways for rotamer interconversion. To aid PES visualization, a set of custom Python-based tools were designed and constructed allowing creation of both graphic and haptic Web3D virtual models for teaching purposes. Increased topological perception and object manipulation were obtained using 3-D rapid prototyped models.
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Luccarelli, James Walter. « Conformational control by intramolecular hydrogen bonding ». Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:48b80a00-cad2-46be-9791-5acab5761ff2.
Résumé :
Hydrogen bonds are directional, non-covalent interactions between hydrogen and electronegative atoms. Although generally weak, these interactions are critical to the stability of many biological systems including proteins and DNA. This dissertation explores small molecules in which an intramolecular hydrogen bond is the key determinant of conformation. Chapter 1 introduces the protein Grb2 SH3C, details its role in cancer signalling, and delineates the idea of peptidomimetics—small molecules which are functionalized to mimic the structure of a peptide and disrupt protein-protein interactions. Chapter 2 describes a virtual screen for binders to Grb2 SH3C. From a library of 6.3 million compounds, 34 were tested in vitro and two found to bind to the protein in two orthogonal assays. Chapter 3 describes mimics of the polyproline II helix using a benzoylurea scaffold. A small library of these compounds was synthesized and tested for binding to Grb2 SH3C using SPR, a competition assay, and NMR. Chapter 4 describes attempts to mimic a 310 helix using benzamide-based peptidomimetics. The synthesis and in vitro evaluation of these molecules as ligands of Grb2 SH3C is described. Chapter 5 uses quantum chemical calculations to assess the energies of a series of molecular switches. These calculations benchmark a range of modern density functional theory calculations, and attempt to quantify the accuracy of these methods for a large, flexible system. The role of solvation, entropy, geometry, and torsional angles are assessed in accurately calculating the energies of the critical hydrogen bonds.
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Dominelli, Whiteley Nicholas. « Hydrogen-bonding and halogen-arene interactions ». Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28824.
Résumé :
Non-covalent interactions are fundamental to molecular recognition processes that underpin the structure and function of chemical and biological systems. Their study is often difficult due to the interplay of multiple interactions and solvent effects common in complex systems. Herein, chapter one provides some general background on the area before presenting a literature review of key, contemporary developments on the use of folding molecules for the quantification of non-covalent interactions. Chapter two investigates the magnitude and extent of energetic cooperativity in H-bond chains. Utilising supramolecular complexes and synthetic molecular torsion balances, direct measurements of energetic cooperativity are presented in an experimental system in which the geometry and number of H-bonds in a chain were systematically controlled. Strikingly, it was found that adding a second H-bond donor to form a chain can almost double the strength of the terminal H-bond, while further extension had very little effect. Computations provide insights into this strong, short-range cooperative effect in a range of H-bonding contexts. Chapters three and four build on the concepts and molecular models discussed in chapter two. Chapter three discusses the effects of interplay and competition between strong H-bond acceptors such as formyl groups and the weaker organofluorine H-bond acceptor. There has been some debate in recent literature about the latter’s ability to accept H-bonds, the work presented shows that although organofluorine is a weak H-bond acceptor, it can have a significant modulating effect on stronger interactions when in direct competition. Chapter four investigates deuterium isotope effects on conformational equilibria governed by non-covalent interactions. The results show that any deuterium isotope effect which exists is less than the margins of experimental error. Finally, chapter five discusses a molecular torsion balance designed to investigate halogen∙∙∙arene interactions. The interaction energies were investigated in a range of solvents and mixtures in order to dissect out the dispersive and solvophobic components of folding. Overall, these interactions were found to be weak. Nonetheless, a model was used to dissect trends in solvophobic and electronic contributions to the binding using multiple linear regression based upon the cohesive energy density and polarisabilities of the solvents.
14
Ghafourian, Taravat. « Investigations of calculated hydrogen bonding parameters ». Thesis, Liverpool John Moores University, 1996. http://researchonline.ljmu.ac.uk/5133/.
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Cornes, Stuart. « Halogen bonding, hydrogen bonding and Lewis acidic receptors for anion recognition ». Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:0725f9c4-ff44-4158-b94e-9bcaf0fa3b4d.
Résumé :
This thesis describes the preparation of acyclic, macrocyclic and interlocked receptors for the recognition of anions in competitive organic and aqueous solvent media. Chapter One introduces the field of anion supramolecular chemistry, with a particular focus on the non-covalent interactions used for anion recognition and the synthesis of mechanically interlocked molecules. Chapter Two discusses the preparation of halogen bonding and hydrogen bonding acyclic and interlocked pyridinium-based receptors. Investigations into their anion selectivity trends are undertaken using 1H NMR titration experiments. The anion sensing properties of analogous hosts containing a fluorescent quinolinium motif are also described. Chapter Three presents the synthesis of acyclic and macrocyclic receptors containing the dicationic 1,2-bis(pyridinium)ethane motif. Attempts towards the preparation of interlocked receptors containing the motif are also discussed. Chapter Four focuses on a series of water-soluble receptors based around functionalised a-cyclodextrins. Isothermal titration calorimetry experiments are used to investigate differences in the thermodynamics of anion binding to halogen bonding and hydrogen bonding analogues. Chapter Five details the preparation of a [2]rotaxane containing a Lewis acidic triarylborane motif. Investigations into its anion binding properties are conducted using multinuclear NMR and UV-visible spectroscopies. Chapter Six provides the experimental details and characterisation data for the compounds discussed in Chapters Two to Five. Protocols for the titration experiments conducted are also described. Full crystallographic data is provided in the Appendix.
16
Chen, Xi. « Designing Acrylic Block Copolymers with Multiple Hydrogen Bonding or Multiple Ionic Bonding ». Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/84961.
Résumé :
The dynamic characteristics of hydrogen and ionic bonding contributes to the reversible properties of acrylic polymers, opening new avenues for designing materials with mechanical strength and processability. These non-covalent interactions function as physical crosslinks, which provide enhanced structural and mechanical integrity to acrylic block copolymers. The strong hydrogen bonding or ionic interaction also directs self-assembly to hierarchical microstructures, which enables many applications including thermoplastic elastomers and energy storage devices. Inspired by complementary hydrogen bonding interactions between nucleobase pairs in DNA, a series of bioinspired nucleobase-acrylate monomers such as adenine acrylate (AdA), thymine acrylate (ThA), cytosine acrylate (CyA) were designed, whose synthesis were afforded by aza-Michael addition. Among those nucleobases, cytosine arises as a unique category. It is not only able to self-associate via weak hydrogen bonds, but also forms quadruple hydrogen-bond bearing units (ureido-cytosine) when functionalized with isocyanates. Reversible addition-fragmentation chain transfer polymerization (RAFT) yielded acrylic ABA triblock copolymers with CyA external hard blocks. A subsequent post-functionalization using hexyl-isocyanate generated the corresponding ureido-cytosine acrylate(UCyA)-containing triblock copolymers. The self-complementary quadruple hydrogen bonding in the UCyA polymers achieved a broader service
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temperature window, while the alkyl chain ends of UCyA units allowed tunability of the mechanical strength to apply as thermoplastic elastomers. In addition, quadruple hydrogen bonding induced stronger propensity of self-assembly and denser packing of the polymers, which contributed to a well-defined ordered morphology and enhanced resistance to moisture uptake. A facile 2-step synthesis provided doubly-charged styrenic DABCO salt monomer(VBDC18BrCl) containing an octadecyl tail. RAFT polymerization allowed the preparation of DABCO ABA block copolymers with defined molecular weights and low polydispersity. Thermal analysis revealed a melting transition of the VBDC18BrCl block copolymer resulting from the side-chain crystallization of the long alkyl tail. Systematic mechanical comparisons between DABCO salt-containing copolymers and the corresponding singly-charged polymer controls demonstrated superior mechanical properties attributable to a stronger ionic interaction between the doubly-charged groups. Morphological characterizations revealed a well-ordered lamellar microstructure and a unique three-phase morphology of the DABCO block copolymers, which involve a soft phase, a hard phase, and an ionic aggregates domain dispersed within the hard domain.Master of Science
17
Cother, Lisa Dawn. « Hydrogen bonding in silanols and their adducts ». Thesis, Imperial College London, 1998. http://hdl.handle.net/10044/1/11984.
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Häggman, Leif. « Chelating surfactants : analysis, hydrogen bonding and structures / ». Uppsala : Dept. of Chemistry, Swedish Univ. of Agricultural Sciences, 2003. http://epsilon.slu.se/a384-ab.html.
19
Cantalapiedra, Nuria Aboitiz. « Intramolecular hydrogen-bonding studies by NMR spectroscopy ». Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366715.
20
Ê¿AÌ„rif, MuhÌ£ammad. « Strong hydrogen bonding in metal fluoride complexes ». Thesis, King's College London (University of London), 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324600.
21
Pearson, Jem M. « Hydrogen-bonding motifs for non-covalent synthesis ». Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:f0630898-35b4-4c74-bc31-dfd252c2ee26.
Résumé :
This work describes the design and synthesis of a set of four organic molecules that are intended to hydrogen-bond to each other in a pairwise manner. The four hydrogen-bonding units, termed ‘A’, ‘B’, ‘C’ and ‘D’, when placed in solution together, are designed so that A binds only to B, and C binds only to D. Each unit does not bind to itself, nor to either of the other two units to which binding is not intended. For example, A binds to B, but not to A, C, or D. Each unit contains an array of four hydrogen-bonds for strong binding to its partner, is designed to be as rigid as possible, as non-tautomeric as possible, and utilises a staggered non-symmetrical architecture. Of the four intended compounds, three were successfully synthesised (A, B and D). Units B and D were soluble in CDCl3, but Unit A was not. Therefore, the design and synthesis of Unit A was amended, and two variants of Unit A that are both soluble in CDCl3 were successfully synthesised. 1H NMR binding experiments were performed between Unit B and each of the two variants of Unit A. Their binding behaviour was described. A binding constant could not be calculated because the units did not bind in a 1:1 fashion.
22
Miller, Allan Harvey 1968. « Predicting the solubility of hydrogen bonding aromatics ». Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/291667.
Résumé :
The AQUAFAC (Aqueous Functional Group Activity Coefficients) method for predicting aqueous activity coefficients proposed by Myrdal et al. (1992) is expanded to include for hydrogen bonding groups: hydroxy, carboxy, nitro and amino. Activity coefficients can be used to estimate aqueous solubility. Using aqueous solubility data, from a number of sources, for a set of subsituted aromatic compounds, group or q values are derived. Group values have been generated for a number of substituents, none have included hydrogen bonding groups (Myrdal et al., 1992,1993). Q values are related to activity coefficients through the following relationship: log gammaw = Sigmaniqi where log gammaw is the log of the activity coefficient, qi is the group value subtituent i and ni is the group frequency. Ortho effects between hydrogen bonding groups is also examined. Intramoleculat hydrogen bonding involving carboxy substituted compounds, in this research, does appear to affect aqueous solubility.
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Al-Mahamad, Lamia Lafta Ghashim. « Supramolecular hydrogels and discrete structures based on metal coordination and hydrogen bonding ». Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/3981.
Résumé :
The complexation of thiolated nucleosides and nucleobases with a range of group 11 metal ions (Au(I), Ag(I), Cu(I/II), was observed to lead to the formation of hydrogels by simple inversion tests. Atomic force and electron microscopy of the xerogels showed, in many cases, the presence of fibres with lengths in the micrometre range and above; this provided evidence for the formation of coordination polymers. This thesis is concerned with the preparation, characterisation and investigation of the physical properties, mainly photoluminescence and conductivity, of these coordination polymers. 2’-Deoxy-6-thioguanosine was successfully synthesised and characterized by UV, IR, Mass, 1H-NMR, and 13C-NMR spectroscopy. The formation of coordination polymers upon reaction of Au(I), Ag(I), and Cu(II) ions with 2’-deoxy-6-thioguanosine and 6-thioguanosine in aqueous media produced hydrogels with up to 97% water+methanol by mass. The Au-6-thioguanosine gel was studied in more detail because of the interest in gold thiolate polymers and the novel properties observed for Au(I)-6-thioguanosine. Fluorescence spectroscopy observed a strong yellow emission (λmax = 606 nm) which is not present in 6-thioguanosine nor in the Au(I) solutions. The optical absorption spectrum of the coordination polymer showed a band at (λmax = 360 nm) assigned to the HOMO-LUMO transition located mainly on the S-Au-S...chain of the polymer. An induced CD band associated with the Au-S chain and an enhancement of the CD signal at shorter wavelengths, for transitions associated with the ligand, suggested the polymer has a helical structure. Further evidence was provided by analysis of the X-ray scattering pattern of the xerogel and atomic force microscopy of single fibres deposited on silicon chips. The observation of long Au(I)-6-thioguanosine fibres and strong photoluminescence suggests some delocalisation of the states associated with the Au-S chains and the possibility of electronic conductivity. This was demonstrated upon oxidative doping of Au(I)-6-thioguanosine xerogels coated over platinum microband electrodes. Treatment with iodine vapour or ([Br(C6H4)3N]SbCl6) in anhydrous acetonitrile were found to result in linear current-voltage characteristics. The temperature dependence of the conductance showed Arrhenius behaviour (over range of temperature 223 to 323 K) with an activation energy of 94 kJ mol-1. V More complex structures based on Au(I)-6-thioguanosine polymers were observed upon synthesising the polymer in the presence of duplex DNA (from calf thymus). The templating of the polymer on DNA produces long, regular, and uniform fibres with a beads-on-a-string morphology. An unusual self-assembly of Au(I)-6-thioguanosine at flat Si surfaces upon simple drop-casting, with slow evaporation was also observed. AFM images of these films showed the formation of well-defined layers, but with each layer comprising long ribbons exceeding the maximum length of the AFM scan (~15 micrometres). Ag(I)-containing hydrogels formed by reactions with 6-thioguanine, 6-mercaptopurine, and 2-thiocytosine were prepared and characterised by AFM, TEM, XPS, X-Ray, FTIR, UV-Vis, and fluorescent spectroscopy. Au(I) 2-thiocytosine was also prepared, but this produced a discrete complex rather than a gel. AFM of the Ag(I) xerogels showed the formation of very long fibres and this was confirmed by TEM images. FTIR and X-ray diffraction studies suggested the metal coordination occurred via S atoms in all three gels. The Au(I) 2-thiocytosine was found to have strong luminescence (λmax 622 nm). A new Ag(I):6-thioethero nucleoside complex was prepared containing 6-methylmercaptopurine riboside (6-MMPR) which was shown by single crystal X-ray diffraction to unexpectedly feature coordination via N7 rather than the thioether sulfur atom. Cu(II) & Co(II):6-methylmercaptopurine(6-MMP) were also synthesised as new discrete complexes. The metals binding was studied by single crystal X-ray diffraction which showed that the binding sites were N3& N9 for Cu(II) ions, and N9 for Co(II) ion in the complexes.
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Chen, Xi. « Exploring Multiple Hydrogen Bonding and Ionic Bonding in the Design of Supramolecular Polymers ». Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/98729.
Résumé :
Supramolecular polymers represent a family of polymeric materials that are held together with dynamic, noncovalent interactions. In contrast to conventional functional polymers that usually have high melt-viscosity due to their covalent nature and chain entanglement, supramolecular polymers combine excellent physical properties with low melt-viscosity, allowing for less energy-intensive processability and recyclability. Dynamic bonding with multiple binding sites, such as multiple hydrogen bonding or multiple ionic bonding, exhibits much stronger binding strength compared to the counterparts containing only a single binding site, thereby allowing for enhanced mechanical integrity to the polymers and facilitate self-assembly. This dissertation focuses on the design of novel supramolecular polymers building from the doubly-charged or quadruple hydrogen bonding (QHB) scaffolds utilizing chain-growth polymerization or step-growth polymerization, as well as elucidate the structure-property-morphology relationships of the polymers.
A 2-step nucleophilic substitution reaction afforded a series of 1,4-diazabicyclo[2.2.2]octane (DABCO)-based styrenic monomers with two pairs of charged groups. An optimized 2-step reversible-addition-fragmentation chain-transfer (RAFT) polymerization synthesized ABA triblock thermoplastic elastomers (TPEs) with a low Tg poly (n-butyl acrylate) central block and a high Tg external charged blocks. Strong ionic interactions between doubly-charged units drove molecular self-assembly to form densely packed, hierarchical microstructures, which contributed to a robust, crosslinked physical network that allows the polymer to retain thermomechanical integrity until degradation. High-resolution single-crystal X-ray diffraction (SCXRD) coupled with powder X-ray diffraction (PXRD) further disclosed a detailed 3-D structural information of molecular arrangement and ion distribution within the charged phase through comparing DABCO-salt monomer single-crystal structure and the corresponding homopolymer XRD pattern. It was found that the physical properties of the DABCO-salt copolymers not only relied on their charge content and architectures but also dependent on their electrostatically-bonded counterions. The size and structure of the counterion determined the strength of dipole-dipole interaction, which significantly impact on thermal property, (thermo)mechanical performance, water affinity, and microstructure.
A cytosine-functionalized monomer, cytosine acrylate (CyA), allowed the synthesis of acrylic ABA triblock TPEs with pendant nucleobase moieties in the external blocks and a low Tg central polymer matrix through RAFT polymerization. Post-functionalization of cytosine (Cyt) bidentate hydrogen bonding sites with alkyl isocyanate, allowed the formation of ureido-cytosine (UCyt) groups in the external block that were readily dimerized through QHB interactions. The UCyt units in the external block enhanced mechanical strength and induced stronger phase-separation of the block copolymers compared to the corresponding Cyt-containing TPE analogs. Facile conventional free-radical polymerization using CyA and subsequent post-functionalization enabled accessibility to random copolymers containing pendant UCyt QHB moieties in the soft polymer matrix. The synergy of the flexible polymer matrix and the dynamic character of QHB groups contributed to the ultra-high elasticity of the polymer and rapid self-healing properties. QHB interactions enabled efficient mechanical recovery upon deformation by facilitating elastic chain retraction to regenerate the original physical network. Finally, one-pot step-growth polymerization through chain extending a novel bis-Cyt monomer and a commercially available polyether diamine using a di-isocyanate extender afforded segmented polyurea series for extrusion additive manufacturing. The molecular design of the polyureas featured soft segments containing flexible polyether chain and a relatively weak urea hydrogen bonding sites in the soft segment and rigid UCyt hydrogen bonding groups in the hard segment. The reversible characteristics of QHB enabled low viscosity at the processing temperature while providing mechanical integrity after processing and reinforced bonding between the interlayers, which contributed to the remarkable strength, elasticity, toughness, and interlayer adhesion of the printed parts.Doctor of Philosophy
This dissertation focuses on designing supramolecular thermoplastic elastomers containing strong noncovalent interactions, i.e., quadruple hydrogen bonds or double ionic bonds. Inspired from noncovalent interactions in our mother nature, a series of bio-inspired monomers functionalized with nucleobase or ionic units were synthesized through scalable reactions with minimal purification steps. Polymerization of the functional monomers through step-growth or chain-growth polymerization techniques affords a variety of supramolecular thermoplastic elastomers with well-defined structures and architectures. These thermoplastic elastomers comprise soft and hard constituents; the former contains low glass transition polymer chains that provide elasticity while the latter contains strong noncovalent units to impart mechanical strength. Varying the soft/hard component ratios enables polymers with tunable physical properties to address different needs. Systematic characterizations of these supramolecular polymers revealed their distinct properties from the polymers containing the covalent or weak noncovalent interactions and facilitate molecular-level understanding of the polymers. Generally, incorporating strong noncovalent interactions increases the temperature for polymer segmental motion and extends thermomechanical plateau windows. Additionally, the strong association strength of those non-covalent interactions promotes microphase separation and self-assembly, contributing to a high degree of structural ordering of the polymers. Moreover, the dynamic characteristics of the noncovalent interactions offer the polymers with reversible properties, which not only enables melt-processability and recyclability of the polymer but also contributes to a series of smart properties, including self-healing, shape-memory, and recoverability. Thus, the molecular design using supramolecular chemistry provides promising avenues to developing functional materials with enhanced mechanical properties, processability, and stimuli-responsiveness for emerging applications.
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Schmidtmann, Marc. « Hydrogen transfer in hydrogen bonded solid state materials ». Thesis, Connect to e-thesis, 2008. http://theses.gla.ac.uk/284/.
Résumé :
Thesis (Ph.D.) - University of Glasgow, 2008.Ph.D. thesis submitted to the Department of Chemistry, Faculty of Physical Sciences, University of Glasgow, 2008. Includes bibliographical references. Print version also available.
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Steinlin, Andreas. « Hydroxyquinolines : hydrogen bonding scaffolds for excited state reactions / ». [S.l.] : [s.n.], 2008. http://opac.nebis.ch/cgi-bin/showAbstract.pl?sys=000286557.
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Rankin, Kathryn N. « A theoretical study of hydrogen bonding involving biomolecules ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ66637.pdf.
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Brom, Coenraad Richard van den. « Aggregation of gold clusters by complementary hydrogen bonding ». [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 2006. http://irs.ub.rug.nl/ppn/292186150.
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Szymczak, Nathaniel Kolnik. « Coordination chemistry of dihydrogen and dihydrogen hydrogen-bonding / ». view abstract or download file of text, 2007. http://proquest.umi.com/pqdweb?did=1400962351&sid=1&Fmt=2&clientId=11238&RQT=309&VName=PQD.
Résumé :
Thesis (Ph. D.)--University of Oregon, 2007.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 307-324). Also available for download via the World Wide Web; free to University of Oregon users.
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Salzameda, Nicholas Thomas. « Syntheses and hydrogen bonding properties of dipyrrinone analogs / ». abstract and full text PDF (free order & ; download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3250684.
Résumé :
Thesis (Ph. D.)--University of Nevada, Reno, 2006."December, 2006." Includes bibliographical references (leaves 120-123). Online version available on the World Wide Web. Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2006]. 1 microfilm reel ; 35 mm.
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Tossell, Katie Jayne. « Catalysis of phosphate ester hydrolysis through hydrogen bonding ». Thesis, University of Sheffield, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.578696.
Résumé :
This thesis describes the investigation of the effect of hydrogen bonding on the rate of phosphoryl transfer in the reaction of diethyl 8-dimethylamino-I-naphthyl phosphate 3 with a nucleophile. The study of the hydrolysis of triester 3 is in the literature; triester 3 is catalysed by the dimethylammonium general acid, with a rate acceleration of almost 106 in comparison to the hydrolysis of diethyl I-naphthyl phosphate. 58 To ascertain whether the reactivity of triester 3 is specific to this system, the methylation of the amine in triester 3 was altered. Triesters diethyl 8- amino-I-naphthyl phosphate 6 and diethyl 8-methyIamino-l-naphthyl phosphate 7 were synthesised and their reaction with water and hydroxylamine was studied. It is concluded that the effect of methylation of the amine on the rate of P-O cleavage in triester 3 is insignificant, and that the hydrogen bond donor ability of the amino proton donor is not an important factor in increasing the rate of P-O cleavage; the energy of triesters 6H+, 7H+ and 3H+ are very similar. The hydrolysis of 8-dimethylamino-l-naphthyl phosphate 5m is also known to exhibit general acid catalysis by the dimethylammonium group." To ascertain whether the effect of methylation of the amine on the rate of p-o cleavage in monoester 5mis also insignificant, the hydrolysis of 8- rnethylamino-I-naphthyl phosphate 27m was studied. It is concluded that methylation of the amino general acid in triester 6H+ and monoester 5m has no significant effect on the rate of phosphoryl transfer, regardless of the different transition states that are formed. By studying the hydrolysis of monoester 36d it is concluded that the reactivity of monoester 5m is also dependent on the proton donor ability of the amino group. The elimination of various functionalised 8-amino-I-tetralone-3-sulfonic acids with hydroxide has been studied. There is a clear difference between the rates of elimination of the tetralones upon varying the proton donor ability of the amino group. No apparent trend relating the rate of elimination to the proton donor ability of the hydrogen bond donor, or to the pKa of the conjugate acid of the tetralones is observed.
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Nieuwenhuyzen, Mark. « Crystal engineering and polymorphism : aspects of hydrogen bonding ». Thesis, Queen's University Belfast, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301029.
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Quinlan, D. J. « Hydrogen bonding in N-ligated copper(II) complexes ». Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262983.
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Mason, Pamela V. « Triazine hosts for metal coordination and hydrogen-bonding ». Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415866.
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Jones, Christopher Raymond. « Hydrogen bonding : from conformational control to asymmetric catalysis ». Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611778.
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Yang, Zhiyi. « Rheology of Miscible Polymer Blends with Hydrogen Bonding ». University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1184881292.
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Willis, Joshua Jerome. « 27th Immunoglobulin Domain : Fold Catastrophes and Hydrogen Bonding ». Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1332855603.
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Steiger, Adam. « Effects of solvent composition on hydrogen bonding equilibria ». Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/8823/.
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Belhekar, A. A. « Conformational and hydrogen bonding behavior of complex molecules ». Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 1990. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2989.
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Snowden, Timothy Scott. « Hydrogen bond involvement in carbon acid pKa[subscript] shifts and intramolecular general catalysis / ». Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3008444.
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Gokcen, Taner. « Molecular engineering of trigonal octupolar materials based on 2,4,6-diarylamino-1,3,5-triazines ». Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-082405-155024/.
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Perera, Manomi Dharshika. « Hydrogen and halogen bonding in co-crystallization : from fundamentals to applications ». Diss., Kansas State University, 2017. http://hdl.handle.net/2097/36209.
Résumé :
Doctor of PhilosophyDepartment of Chemistry
Christer B. Aakeroy
The impact of the molecular electrostatic potential values (MEPs) in halogen and hydrogen bond interactions were explored using two acceptors with multiple acceptor sites with twelve hydrogen-bond donors, five halogen bond donors and four mixed halogen and hydrogen bond donors. The results suggested if the difference between the two acceptor sites is above 38 kJ/mol both hydrogen and halogen bond donors prefer the acceptor site with the highest MEP value and this selectivity was lost if the difference is below 26 kJ/mol. To examine the potential of halogen-bond donors in organocatalysis, a halogen-bond donor molecule was synthesized and the catalytic activity was measured using a benchmark Ritter type solvolysis reaction. Results suggested the catalytic activity of the halogen-bond donor molecule with > 90 % conversion of the product with the use of a stoichiometric amount of the catalyst for 96 hrs. Successful use of the control molecules confirm that the catalytic activity is an outcome of having halogen-bond donors in the molecule. The benefit of using a structural mimic in landscaping the structural outcomes of poorly soluble molecules was explored using an anticancer drug erlotinib. A structural mimic was synthesized by maintaining all binding sites that are important to design a structural landscape and the structural outcomes were analyzed using five FDA approved dicarboxylic acids. The results suggested that the structural outcomes of the mimic can be related to the actual drug erlotinib. Solubility and thermal behavior analysis of the co-crystals also suggested that with the systematic changes of the co-crystallization agent, it is possible to make predictable changes to the physical properties. To observe the effect of co-crystallization technology in reducing the chemical reactivity and sensitivity of an energetic compound dinitrobenzotriazole, a series of co-crystallization experiments was carried out using fourteen nitrogen and oxygen based acceptors. Four co-crystals were obtained and the acceptors were identified as supramolecular protecting groups which led to successful diminish of chemical instability and decreased impact sensitivity. Hygroscopicity and chemical reactivity of tetranitrobisimidazole, a potential RDX replacement, was successfully decreased by protecting the acidic N-H protons in the molecule by introducing suitable co-formers. Introduction of the N-oxide based acceptors into the system enhanced the stability while retaining most of the desirable energetic properties.
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Arman, Hadi D. « Strategies for expanding the halogen bonding periodic table and designing complementary halogen/hydrogen bonding synthons ». Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1219848304/.
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Cui, Lu. « Hydrogen Bonding and Cucurbituril Complexation as Self-Assembly Mechanisms ». Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_dissertations/450.
Résumé :
The supramolecular interactions of small organic molecules with different host molecules are investigated in this dissertation. Additionally, the author also describes the self-assembly mechanisms in hydrogen bonding motif. These studies were carried out by many techniques including, NMR, cyclic voltammetry, steady state voltammetry, mass spectroscopy, UV-visible spectroscopy and fluorescence spectroscopy. Chapter 1 introduces the science of supramolecular chemistry and the background of cucurbiturils, one of the most important host molecules studied in this research work. It describes the structures and binding behaviors of each host molecule. Additionally, the selectivity and binding properties in the host-guest interactions involved cucurbiturils are discussed. Chapter 2 compares the electrochemical properties of cationic and neutral ferrocene derivatives upon addition of cucurbiturils. It is observed that the cationic ferrocene compounds bind to cucurbit[7]uril much stronger compared to the neutral ferrocene compounds. The positive charged side chains favor to interact with cucurbit[7]uril portals and thus stabilize the complexes. Besides, the author describes a simple analytical method to determine the binding constants by a competitive binding with a standard reference compound, cobaltocenium, which is reported to bind strongly to cucurbit[7]uril. Chapter 3 described the research of the pH-dependent binding affinity between cucurbit[7]uril and ferrocene guests. The electrochemical behavior of ferrocene moiety in aqueous solution was investigated by cyclic voltammetry in the presence of cucurbit[7]uril in acidic and basic environment respectively. The protonation and deprotonation processes affect the binding behaviors of the ferrocene residues with cucurbit[7]uril. Chapter 4 describes the synthesis and characterization of a new series of 4-phenyl-pyridinium derivatives. These compounds contain a phenyl-pyridinium residue which is favorable to be bound by cucurbit[8]uril. The 1:1 and 1:2 host-guest binding stoichiometries are both observed by UV-visible spectroscopy. These new compounds can be dimerized encapsulated inside the cucurbit[8]uril portals without being electrochemical reduced. Chapter 5 is a brief introduction into the science of hydrogen bonding. This chapter investigates the application of multiple hydrogen-bonding in supramolecular chemistry extensively. Multiple hydrogen bonds with their directionality and reversibility are of great interest and importance in the design and investigations of well-defined supramolecular assemblies. The potential of hydrogen bonding is limitless and is still developing. Chapter 6 describes the synthesis and photochemical behaviors of a series of ureido-pyrimidione derivatives. All of the DDAA derivatives form stable, non-covalent dimers in non-polar solvents. The dimeric molecular assemblies of these hydrogen bonding motifs in their DDAA pyrimidinedione units are investigated by NMR, X-ray crystallography, fluorescence spectroscopy and computations. Additionally, their hetero-dimerization is well studied by fluorescence spectroscopy. The observation and comparison of fluorescence quenching on the photochemical fluorophore for each compound by ferrocene-DDAA and isopropyl-DDAA reveal the electron transfer process through the quadruple hydrogen bonding motifs.
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Murguly, Elisa. « Programming supramolecular systems using hydrogen bonding and metal chelation ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ60476.pdf.
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Li, Hui. « N-heteroaromatic acid adlayer structures under hydrogen bonding influence ». College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/6649.
Résumé :
Thesis (Ph. D.)--University of Maryland, College Park, 2006.Thesis research directed by: Chemistry. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Maccallum, Peter Hugh. « Hydrogen bonding and the stability of the polypeptide backbone ». Thesis, University of Glasgow, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360133.
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Boissonnet, Michel-Franck. « Hydrogen-bonding ferrocene derivatives for molecular recognition and organocatalysis ». Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6121/.
Résumé :
The aim of this project was to prepare novel ferrocene-based Hydrogen-bonding receptors and to study them in the electrochemical sensing of neutral compounds and in organocatalysed transformations. The synthesis and characterisation of 2-ferrocenyl oxazoles via gold chemistry to access a new H-bonding motif for electrochemical sensing was successfully achieved. However the targeted structure bearing a secondary amine at the 4-position of the oxazole, was found to be highly unstable and unsuitable for sensing applications. Further studies on ferrocene-based H-bonding systems towards their application in asymmetric organocatalysis were also carried out. Different chiral and achiral ferrocene-(thio)ureas were prepared and tested in four organic reactions. Their performances in the Henry and in the Morita-Baylis-Hillman reactions gave acceptable yields but did not show significant enantioselectivities. A bi-functional ferrocene-thiourea was found to be effective in the enamine co-catalysed aldol reaction of acetone and \(trans-β\)-nitrostyrene, and in the double Michael cycloaddition of ω-nitropentenoate methyl and \(trans-β\)-nitrostyrene, leading to a tetrasubstituted cyclopentane. The H-bonding properties of the ferrocene-(thio)ureas with carboxylates was also studied by \(^1\)H NMR spectroscopy. Finally, approaches towards the preparation of ferrocene-based boronate-ureas were investigated.
49
Metteau, Laurent. « Redox properties of metal complexes with internal hydrogen bonding ». Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/15375.
Résumé :
In this thesis we incorporate hydrogen bonding features NH2 (Am), NHCH2tBu (Np), and NHCOtBu (Piv) in the pyridine 6th position of the tripodal ligand TPA (tris(2-pyridylmethyl)amine, L). Thus, thirteen ligands LX-n (X = Am, Np, Piv; n = 0, 1, 2, 3) derived from and including TPA have been made. Also, one and two amino groups have been introduced in a similar position of the ligand N,N-Bis(2-pyridilmethyl)-N-(glycine)amine (BPG), (one amino group, APPG and two amino groups, BAPG) have been made. The structures of several [LMCl]0 or +1 complexes (M = Zn(II), Cu(I), Cu(II)) were determined by X-ray crystallography ([(LAm-3)ZnCl]BPh4, [(LPiv-3)CuCl], and [(BAPG)CuCl]Cl). All these complexes exhibit intramolecular NH…Cl hydrogen bonding. For the Zn(II)Cl complexes of the LX-n ligands, the main structural changes caused by hydrogen bonds are the lengthening of the Zn-Cl and the Zn-NPy bonds and shortening of the Zn-NAx bond. In general, these changes are more significant when the number of hydrogen bonds increases, and vary according to their strength. In related Cu(I) and Cu(II) complexes, an important factor affecting the strength of the N-H…Cl hydrogen bonds is the oxidation state of the metal centre. Thus, the N-H…Cl interaction is stronger in the Cu(I) oxidation state. The [(LX-n)CuCl]+ complexes were used to investigate the effect of the N-H…Cl hydrogen bonding on the redox properties of the metal centre. Cyclic voltammetry studies showed that the reduced state of the metal centre is stabilised when stronger and more numerous hydrogen bonds are introduced. The half wave potential of the Cu(II)/Cu(I) redox couple shifted to more positive values by 58 mV in [(LAm-1)CuCl]+ to 541 mV in [(LPiv-3)CuCl]+ relative to the TPA complex. We estimated that in these complexes, hydrogen bonds can contribute as much as 30% to the stabilisation of the Cu(I) over the Cu(II) oxidation state. The individual contribution of each hydrogen bond towards stabilising the Cu(I) state is greater the fewer interactions. The effect of hydrogen bonding on the redox properties of zinc-bound DTBC (3,5-di-tert-butylcatechol) in [LX-nZnDTBC) complexes was also investigated. The X-ray structure of [LAm-1ZnDTBC] showed internal N-H…O hydrogen bonding. Cyclic voltammetry and spectroelectrochemical studies showed that the reduction of DTBC complexes occurs at more positive potentials in the presence of hydrogen bonds. For [LPiv-3ZnDTBC], the reduction of DTBC was facilitated by as much as 470 mV relative to the TPA complex, and is accompanied in this case by a binding enhancement of 3.9 x 106 fold. These changes are compared with those obtained by changing the metal or its coordination sphere and with hydrogen bonds alone.
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Garfitt, Jason Michael. « Hydrogen bonding and covalent coupling in adsorbed molecular monolayers ». Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/27728/.
Résumé :
This thesis examines multiple different molecular networks adsorbed on several different substrates, namely, highly oriented pyrolytic graphite (HOPG), Au(111) and graphene. STM investigations into hydrogen-bonded structures formed by closely related tetracarboxylic acid molecules were performed. The molecule pterphenyl-3,5,3,5-tetracarboxylic acid (TPTC), which is known to form random tiling networks, was observed on a graphene on copper substrate. The network formed from deposition of TPTC from nonanoic acid was examined statistically. Aqueous solutions of TPTC were also examined on HOPG where a new structure, distinct from the random tiling, was observed. Aqueous solutions of related molecules biphenyl-3,3',5,5'-tetracarboxylic acid (BPTC) and quaterphenyl-3,3',5,5'-tetracarboxylic acid (QPTC), were also studied on HOPG. QPTC formed a similar structure to the aqueous solutions of TPTC, but BPTC formed two different phases, one of which was a kagome network. Addition of nonanoic acid to a dried network of TPTC deposited from aqueous solution resulted in solvent induced recrystallisation into a random tiling network comparable to that observed on graphene on copper, which was statistically analysed. Studies investigating the potential for covalent bonded molecular networks identified two distinct phases of the molecule 1,3,5-Tri(4-bromophenyl-benzene (TBPB)) adsorbed on Au(111). Concentration variation indicates an island based growth mechanism for these domains from solution. Dimerisation of TBPB was achieved by deposition onto heated substrates and a discussion of possible reasons for the reaction termination at dimers is provided. Attempts to repeat the TBPB experiments on graphene on copper failed due to excessive corrosion. Variations using larger molecules failed due to lack of solubility. Preliminary experiments on 10,10'-dibromo-9,9'-bianthryl (DBrBA) showed promise but were irreproducible, however micron scale dendritic structures were observed suggesting poor compatibility with the solvent. Finally, a discussion of the development of a nickel catalysis based graphene fabrication method is given and the limits of what is achievable with this method are discussed. The results from this thesis highlight the importance of solvent selection for the future understanding of molecular network fabrication. We also demonstrated the feasibility of covalently bonded networks prepared in ambient conditions.