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  • 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

The effects of certain anions on the linear starch-triiodide blue complex

Rhoads, S. C. January 1958 (has links)
Call number: LD2668 .T4 1958 R52
22

ALKYLATION AND OXIDATIONS OF SYMMETRICAL DIMETHYLENEBIPHENYL AND RELATED DIANIONS (CYCLOPHANE, BIPHENYLOPHANE, NMR, CONFORMATION).

WHITE, JAMES JEFFREY. January 1986 (has links)
Bis-benzyl dianions were prepared from the three symmetrical dimethylbiphenyls in yields of 79-86%, and shown to react with a variety of electrophiles on the benzylic carbons. Electrophiles included dimethyl and diethyl sulfate, isopropyl bromide, t-butyl iodide, allyl chloride, trimethylsilyl chloride, trimethylgermyl bromide, and trimethyltin chloride. Reaction of the dianions with (alpha),(omega)-dihalides provides an excellent route to n.0 - and n.0.n.0 cyclophanes. An X-ray study on 14.0 paracyclophane showed it to have a conformation different from that observed in solution by NMR; MM2 calculations were used in determining what the solution conformation is likely to be. Oxidation of the dianions produced the monomer dihydrophenanthrene from the ortho isomer, dimer 2.0.2.0 metacyclophane from the meta isomer, and polymer from the para isomer. An X-ray study on 2.0.2.0 metacyclophane showed it to have the same conformation in the crystal as is observed in solution by NMR. An NMR method for determining the angle of twist in a biphenyl based on the chemical shift of the ortho hydrogens was developed. Many oxidizing agents were evaluated for the oxidation of the dianion from 2,3-dimethyl-1,3-butadiene to 1,2,5,6-tetramethylenecyclooctane; cupric bromide was found to be the best.
23

Supramolecular architectures of transition metal dipicolinates

Felloni, Marina January 2003 (has links)
No description available.
24

First principle studies on solvation and electronic structures in M⁻L[subscript n], with M⁻=Li⁻ and Na⁻, L=H₂O and NH₃, and n=1-10. / 阴离子簇合物 M⁻L[subscript n],( M⁻= Li⁻, Na⁻, L=H₂O, NH₃,;n=1-10)中溶剂化作用和电子结构的第一原理研究 / First principle studies on solvation and electronic structures in M (⁻) lin, with M (⁻)=lithium (-) and sodium (-), L=H2O and NH3, and n=1-10 / CUHK electronic theses & dissertations collection / Yin li zi cu he wu M⁻L[subscript n], (M⁻= Li⁻, Na⁻, L=H₂O, NH₃,;n=1-10) zhong rong ji hua zuo yong he dian zi jie gou de di yi yuan li yan jiu

January 2012 (has links)
本文运用化学计算软件Gaussian03以及基于赝势和平面波基组的从头计算分子软件VASP, 研究了阴离子簇合物M⁻L[subscript n], (M⁻ = Na⁻, Li⁻,; L = H₂O, NH₃ ; n = 1-10) 中的电子结构和溶剂化作用。 / 文中选用基于密度泛函理论的B3LYP方法和6-311++G** 基组, 从Na⁻ 离子和Li⁻ 离子分别与不同溶剂分子 (H₂O和NH₃) 的相互作用入手,探讨以这类气态团簇化合物作为载体的体系中,溶解于其中的两个电子之间的相互作用以及电子与溶剂分子之间的相互作用。对于因溶剂分子极性的差异,导致形成不同形态的簇合物,进而影响了溶解于其中的电子对状态的研究,为实验上进一步探究被溶解的电子对提供了有利的理论依据。 / 在阴离子簇合物Li⁻(H₂O)[subscript n]中, 锂负离子和氧原子的强相互作用使得锂负离子被水分子包围。当n = 10,锂负离子的两个外层电子转移到水分子团簇中,并且电子对可以以单重态或三重态的电子态稳定存在。与之相反,在阴离子簇合物Na⁻(H₂O)n中,钠负离子的两个外层电子没有向溶剂中转移,钠负离子更倾向于与水分子团簇表面的氢原子相互作用而稳定在团簇表面。 / 在以氨分子为溶剂的阴离子簇合物Na⁻(NH₃)n和Li⁻(NH₃)n中, 金属负离子Na⁻ 和Li ⁻的两个外层电子随着溶剂分子的增加逐渐从金属离子上转移到溶剂 中。事实上,当n = 10时,簇合物Na⁻(NH₃)[subscript n]和Li⁻(NH₃)[subscript n]形成了两个溶解中心:被溶剂分子包围的金属阳离子,及其附近分散在溶剂分子中的电子对。这对电子可以以单重态或三重态的电子态稳定存在。与以水为溶剂的簇合物Na⁻(H₂O)[subscript n]和Li⁻(H₂O)[subscript n]不同的是,在Na⁻(NH₃)[subscript n]和Li⁻(NH₃)[subscript n]中,被溶解电子对更加弥散,广泛分布于溶剂分子中。 / The solvation and electronic structures in M⁻Ln₂, M⁻ = Li⁻ and Na⁻, L = H₂O and NH₃, and n = 1-10 were explored computationally by quantum chemistry calculation using Gaussian 03 package and by density functional theory based ab initio molecular dynamics simulation (AIMD) method with pseudopententials and a plane wave basis set using Vienna Ab Initio Simulation package (VASP). / Interactions of Na⁻ and Li⁻ anions in different solvent molecules, H₂O and NH₃, were calculated by B3LYP method with a basis set of 6-311++G** in order to explore the possibility that these clusters could serve as gas-phase molecule models for the solvation of two electrons. Such models would capture the electron-electron interaction in a solution environment. / For Li⁻(H₂O)[subscript n], the Li⁻ is buried in the water cluster due to the strong Li-O interaction, and by n = 10, the two loosely bound s electrons are indeed detached from lithium, and they could in either the singlet (spin-paring) or the triplet (spin-coupling) state. In contrast, for Na⁻(H₂O)[subscript n], the electron pair stays on the sodium, and the Na⁻ stays on the cluter surface, which is solvated by no more than 4 hydrogen atoms. The solvent-solvent interactions are favored as the water molecules from structures similar to observed in water anions. The formation of a solvated electron pair and the variation in solvation structures make these two cluster series interesting subjects for further experimental investingation. / With two s electrons, the Na⁻(NH₃)[subscript n] and Li⁻(NH₃)[subscript n] clusters are unique in that they capture the important aspect of the coupling between two solvated electrons. By first principles calculations, we demonstrate that the two electrons are detached from the metal by n = 10, which produces a cluster with a solvated electron pair in the vicinity of a solvated alkali cation, and the two electrons could also exist in both singlet and triplet state. They are quite distinct from the hydrated anionic clusters Na⁻(H₂O)[subscript n] and Li⁻(H₂O)[subscript n], in that the solvated electrons are delocalized and widely distributed among the solvent ammonia molecules. The Na⁻(NH₃)[subscript n] and Li⁻(NH₃)[subscript n] series therefore provide another interesting type of molecular model for the investigation of solvated electron pairs. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Zhang, Han. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / TITLE PAGE --- p.I / ABSTRACT --- p.II / 论文摘要 --- p.IIV / ACKNOWLEDGEMENTS --- p.VI / CONTENTS --- p.VII / LIST OF TABLES --- p.X / LIST OF FIGURES --- p.XIII / Chapter Chapter One --- General Research Background / Chapter 1.1 --- General Introduction --- p.1 / Chapter 1.2 --- Electron in polar solvent --- p.1 / Chapter 1.2.1 --- Electron in water molecules --- p.1 / Chapter 1.2.2 --- Electron in ammonia molecules --- p.6 / Chapter 1.3 --- Experimental background of metal anion --- p.9 / Chapter 1.3.1 --- Li⁻(H₂O)[subscript n] and Na⁻(H₂O)[subscript n] --- p.9 / Chapter 1.3.2 --- Li⁻(NH₃)[subscript n] and Na⁻(NH₃)[subscript n] --- p.11 / Chapter 1.4 --- Scope of this thesis --- p.13 / Chapter 1.5 --- References --- p.14 / Chapter Chapter Two --- Theoretical Background / Chapter 2.1 --- Introduction --- p.18 / Chapter 2.2 --- The Schrödinger Equation and Born-Oppenheimer Approximation --- p.19 / Chapter 2.3 --- Hartree-Fock Theory --- p.20 / Chapter 2.4 --- Post-HF methods --- p.24 / Chapter 2.5 --- Density Functional Theory --- p.25 / Chapter 2.5.1 --- Kohn Sham (KS) scheme --- p.26 / Chapter 2.5.2 --- Local Density Approximation (LDA) --- p.29 / Chapter 2.5.3 --- Generalized Gradient Approximation (GGA) --- p.30 / Chapter 2.5.4 --- Hybrid Functionals --- p.30 / Chapter 2.6 --- DFT based ab initio Molecular Dynamics (AIMD) --- p.31 / Chapter 2.6.1 --- Plane Wave Basis Set --- p.34 / Chapter 2.6.2 --- Pseudopotentials and Projector Augmented Wave Method --- p.35 / Chapter 2.6.3 --- Molecular dynamics at constant temperature --- p.39 / Chapter 2.7 --- References --- p.40 / Chapter Chapter Three --- The identification of a solvated electron pair in the gaseous clusters of Na(H2O)n and Li(H2O)n / Chapter 3.1 --- Introduction --- p.42 / Chapter 3.2 --- Computaional methods --- p.45 / Chapter 3.3 --- Results and discussion --- p.46 / Chapter 3.3.1 --- Structure and energy for Na⁻(H₂O) and Li⁻(H₂O) --- p.46 / Chapter 3.3.2 --- H end structure for Na⁻(H₂O)[subscript n] --- p.52 / Chapter 3.3.3 --- O end structure for Li⁻(H₂O)[subscript n] --- p.58 / Chapter 3.3.4 --- Triplet structures for Li⁻(H₂O)[subscript n] --- p.64 / Chapter 3.3.5 --- Comparison between singlet and triplet Li⁻(H₂O)[subscript n] --- p.69 / Chapter 3.4 --- Conclusion --- p.73 / Chapter 3.5 --- References --- p.74 / Chapter Chapter Four --- The solvation of two electrons in the gaseous clusters of Na⁻(NH₃)n and Li⁻(NH₃)[subscript n] / Chapter 4.1 --- Introduction --- p.78 / Chapter 4.2 --- Computaional methods --- p.80 / Chapter 4.3 --- Results and discussion --- p.82 / Chapter 4.3.1 --- n = 1 --- p.82 / Chapter 4.3.2 --- H End Structures for Na⁻(NH₃)[subscript n] --- p.87 / Chapter 4.3.3 --- N End Structures for Li⁻(NH₃)n and Na⁻(NH₃)[subscript n] --- p.90 / Chapter 4.3.4 --- Triplet N End Structures for Li⁻(NH₃)[subscript n] --- p.97 / Chapter 4.3.5 --- Comparison between singlet and triplet Li⁻(NH₃)[subscript n] --- p.103 / Chapter 4.4 --- Conclusion --- p.105 / Chapter 4.5 --- References --- p.106
25

Eletron planar submetido a um campo magnético intenso /

Lautenschleguer, Ivan José. January 1994 (has links)
Orientador: Abraham Hirsz Zimerman / Mestre
26

Synthesis, structure, and weakly coordinating nature of new carborane anions. / CUHK electronic theses & dissertations collection

January 2000 (has links)
Chi-wing Tsang. / "July 2000." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (p. 151-160). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.
27

First principles studies on the solvation and dissociations of hydrated di-anions (SO₄²⁻ and C₂O₄²⁻) and of solvated sodium. / CUHK electronic theses & dissertations collection

January 2006 (has links)
Compared to SO42-(H2O)n, the solute-solvent interaction is favorable by C2O4 2- (H2O)n, n = 6∼12, due to two charges separation and more space in C2O42-. Because of the extensive hydration bonds, the stepwise solvation energy is around 15 kcal/mol even for larger clusters. The solvation dynamics for C 2O42-(H2O)n is influenced by the coupling between torsional movement along C-C bond and solute-solvent interaction. / For Na(H2O)n, the "constant IP" observed experimentally for Na(H2O)n is due to autoionization through Rydberg transition induced by the release of large relaxation energy after the removal of unpaired electron. In contrast, the reorganization is less extensive in Na(NH3)n, as both the electron-NH3 and NH 3-NH3 interactions are weaker, and the structure of Na(NH 3)n is determined by the maximization of Na+-NH 3 interaction. The autoinization is no important and the threshold measured in experiment is indeed for ionization of Na(NH3)n. / In the size-dependant charge separation of SO42-(H 2O)n with n = 3∼7, the key factor governing the charge separation is the difference in the strength of solvation interaction: while interaction with water is strong for SO42- and OH-, it is relatively weak for HSO4-. It gives rise to a barrier for charge separation as SO42- is transformed into HSO4- and OH-, although the overall reaction energy is exothermic. The barrier is high when more than two H2O are left to solvate HSO4-. The entropy is another important factor, which leads to the eventual switch-off of charge separation as cluster size increases. / The equilibrium structures of SO42-(H 2O)n with n = 6∼12 are determined by the competition between the solute-solvent and solvent-solvent interactions. Facilitated by SO42- in symmetry, the extensive hydrogen bonds are formed. The stepwise solvation energy is quite large (often exceeding 15 kcal/mol). AIMD simulation shows "crowding" effects in the first solvation of SO42-(H2O)12 at raised temperature. / The structure and solvation of hydrated di-anion (SO4 2-, C2O42-) clusters and solvated Na clusters are explored computationally by the quantum chemical calculation using Gaussian programme, and by the density functional theory based ab initio molecular dynamics (AIMD) method using Vienna Ab Initio Simulation Package (VASP). / Gao Bing. / "May 2006." / Adviser: Zhi-feng Liu. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6420. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 131-139). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.
28

The influence of anion-pi interactions between multi-atomic anions and pi-acidic ring systems on the self-assembly of coordination compounds

Schottel, Brandi Lee 15 May 2009 (has links)
Anion-π interactions, weak attractions between anions and π-acidic ring systems, have become an important topic in supramolecular chemistry within the past five years. Although a variety of computational studies have been undertaken by several groups to investigate the nature of these interactions, no comprehensive experimental investigations had been performed until the completion of the work described herein. The results presented in this dissertation indicate that anion-π interactions involving large complex anions are controlling elements in self-assembly reactions with cations that involve π-acidic ring systems. Syntheses performed with the ligand 3-6-bis(2’-pyridyl)-1,2,4,5-tetrazine, or bptz, with M(II) first row transition metal salts (M = Mn, Fe, Ni, Cu, and Zn), produced self-assembled complexes that varied in shape and M:ligand ratio based on the presence of particular anions. Through a series of solution and structural studies, it was determined that the cationic polygons are templated by the size and shape of the specific anions during self-assembly. A close inspection of the bptz complexes in the solid state indicated that the anions were participating in anion-π interactions with the π-acidic central tetrazine ring of the ligand. To show that these anion-π interactions were indeed important, reactions of bptz ligand as well with 3,6-bis(2’-pyridyl)-1,2-pyridazine (bppn) with Ag(I) salts were performed to compare the effect that specific anions had on self-assembly interactions between similar ligands with different π-acidities. The results indicate that the Ag(I) complexes that included the π-acidic tetrazine ring are strongly influenced by the anion presence, while those complexes that were synthesized with the similarly shaped, but electroneutral bppn ligand only relied on the anions for charge-balance. To better understand the anion-π interactions in the obtained bptz complexes, a computational study was performed on systems with the polyatomic anions [BF4]- and [PF6]- interacting with simple heteroaromatic rings of varying degrees of π-acidity. Based on the final optimized complex geometries and Atoms in Molecules (AIM) critical point analyses, it was determined that anion-π interactions involving multiatomic anions interact with π-systems in different orientations based on the symmetry of the ring system in the complex.
29

Etude de l'influence de la rétention chimique sur la diffusion d'espèces anioniques dans les milieux argileux compacts

Bazer-Bachi, Frédéric Sardin, Michel January 2005 (has links) (PDF)
Thèse de doctorat : Génie des procédés : Vandoeuvre-les-Nancy, INPL : 2005. / Titre provenant de l'écran-titre. Bibliogr.
30

Calix[4]arènes phosphoniums et ammoniums Synthèse et étude des interactions ligand-anion /

Pomećko, Radosław. Arnaud, Françoise. Bochenska, Maria. January 2007 (has links) (PDF)
Thèse de doctorat : Chimie supramoléculaire : Strasbourg 1 : 2007. Thèse de doctorat : Chimie supramoléculaire : Gdansk University of Technology : 2007. / Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre. Notes bibliogr.

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