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The Fries rearrangement : added-ion effects and spectroscopic investigationsWaddington, C. R. January 1985 (has links)
No description available.
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Neutral and Cationic Main Group Lewis Acids - Synthesis, Anion Complexation and Redox PropertiesDorsey, Christopher L. 2009 May 1900 (has links)
The primary goal of this research concerns the synthesis and characterization of hybrid
main group Lewis acids. Initially, the focus of this work was on the synthesis of
derivatives possessing unusual bonding interactions enforced by a rigid 1,8-
naphthalenediyl scaffold. After discovering a route to a new dilithio reagent, silicon
based derivatives featuring R3Si-F->CR3
+ and R3C-H->SiFR3 interactions of 2.703(2)
and 2.32(2) Angstrom respectively were successfully synthesized and fully characterized.
Another hybrid Lewis acid based on the 1,8-naphthalenediyl scaffold that was studied
was a trinuclear B2/Hg Lewis acid. This molecule has been shown to bind two fluoride
anions sequentially, and the binding events can be followed by differential pulsed
votammetry.
The final part of this work concerns the reactivity and redox behavior of main group
systems. It has been shown that the p-phenylene linker in 4-dimesitylboryl-1-
diarylmethylium benzenes effectively reduces electrochemical communication between
the carbocation and borane moieties when compared to systems without the linker.
Reduction of these species produces a derivative whose EPR signal is only slightly
influenced by the ^11 B center. These findings have been further substantiated by
theoretical calculations. Finally, the redox properties of alpha-phosphonio- and alpha- phosphonyl-carbocations have been studied. Chemical reduction of both species leads to
a predominately carbon centered radical with coupling to the ^31P center of 18 and 19.7 G
respectively. The alpha-phosphonio carbocations, however, also undergo ligand exchange
reactions with pyridine derivatives suggesting that these species can also be referred to as
ligand stabilized carbodications.
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Preparation and use of chiral borane lewis acidsMahal, R. S. January 1988 (has links)
No description available.
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Trimeric perfluoro-ortho-phenylene mercury as a building block for supramolecular materialsHaneline, Mason Reames 12 April 2006 (has links)
Trimeric perfluoro-ortho-phenylene mercury (1) constitutes one of the simplest trifunctional Lewis acidic hosts. Cooperative effects arising from the proximity of the mercury(II) centers, the electron-withdrawing properties of the backbone and the accessibility of the electrophilic sites leads to the facile complexation of neutral and electron rich substrates. The planarity of the structure as well as its overall polarizability compounded with relativistic effects at mercury also permits the occurrence of non-covalent interactions. The main objective of this dissertation was to explore the potential of 1 as a building block for supramolecular materials.
Compound 1 was investigated using single crystal x-ray diffraction and was found to display a rich polymorphism. The electronic structure, probed by DFT methods, shows that the LUMO of 1 has a large contribution from the mercury 6p orbitals and features a large lobe protruding above and below the center of the trinuclear mercury core. Complexes in which two nitronyl nitroxide radicals (NIT-Ph = 2-(phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) coordinate to the trinuclear core of 1 above and below the Hg3 plane reveal that 1 does not significantly mediate magnetic interactions.
The ability of 1 to complex π-basic molecules such as tetrathiafulvalene (TTF), toluene, o-xylene, m-xylene, p-xylene, mesitylene, biphenyl, naphthalene, acenaphthalene, anthracene, pyrene, triphenylene, perylene, and coronene was also investigated and show that 1 and arenes form extended binary stacks in which the two components alternate. The photoluminescence observed in some of these supramolecular complexes corresponds to the phosphorescence of the arene indicating a mercury heavy atom effect. Complexation of 1 in solution was observed with hexaalkoxytriphenylenes (HATn, n = 1, 6) by fluorescence and NMR spectroscopy.
Finally, compound 1 forms electrophilic double sandwich structures with ferrocene and nickelocene in which a molecule of 1 caps each of the Cp ligands. The nickelocene adduct is stabilized towards oxidation, and the photophysical and magnetic properties indicate the occurrence of a mercury heavy atom effect.
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The Sulphur Nitrogen Bond 1. Lewis Acid Adducts of Tetrasulphur Tetranitride 2. Reaction of Sulphur with dl-α-MethylbenzylamineChan, Cheong Hoi 10 1900 (has links)
<p> Adducts of aluminum chloride and aluminum bromide with tetrasulphur tetranitride have been prepared and characterized. The reaction of trimethylaluminum and triethylaluminum with tetrasulphur tetranitride has been studied. The reaction of sulphur with α-methylbenzylamine has been investigated, and the reaction mechanism proposed by Sasaki for benzylamine reacting with sulphur has been found to be consistent with the data, provided certain limitations are imposed. </p> / Thesis / Master of Science (MSc)
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Lewis Acid Catalyzed CycloadditionsKennedy, Roger A. 09 1900 (has links)
<p> This thesis describes an attempt to develop a potentially useful route to
seven-membered carbocycles. α-Diketones and their enol ether derivatives were proposed to be suitable three-carbon cycloaddition dienophiles when complexed with a Lewis acid. Reaction with 1,3-dienes should then lead to the desired cycloheptyl system.</p> <p> 1H-NMR and 13C-NMR studies were used to determine the stoichiometry and charge delocalization of complexes formed between 2,3-butanedione, 1,2-cyclohexanedione,
2-methoxy-cyclohex-2-en-1-one and the Lewis acids TiCl4 and SnCl4. Observations
from these studies suggested that 1,2-cyclohexanedione and 2-methoxy-cyclohex-2-en-1one
could behave as substituted allyl cations when complexed with TiCl4 or SnCl4.</p> <p> Reaction of the 1,2-cyclohexanedione/TiCl4 and 2-methoxy-cyclohex-2-en-1one/
TiCl4 complexes with 1 ,3-butadiene gave rise to six-membered carbocycles from
[4C+2C] cycloadditions. The reaction of 2,3-butanedione-mono-trimethylsilyl enol
ether/TiCl4 complex with 1,3-butadiene gave a mixture of the [4C+2C] and [4C+3C]
cycloaddition products.</p> / Thesis / Master of Science (MSc)
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Lewis acids for the activation of pyridines for further functionalisationAbou-Shehada, Sarah January 2015 (has links)
This thesis outlines work carried out over the past three years concerning the development of an experimentally simple, sustainable catalytic method for the functionalisation of pyridines by means of a zinc nitrate based Lewis acid. It encompasses reaction discovery and optimisation, determination of the scope of the method through nucleophile and substrate screens as well as investigations into the mechanism by which the reaction takes place. Chapter 1 gives a general overview of the industrial relevance of pyridine functionalisation as well as the synthetic methods for the synthesis of ring functionalised pyridines, covering traditional stoichiometric aromatic substitution methods, transition metal catalysed cyclisations, standard catalytic methods for the functionalisation of pyridines: Buchwald-Hartwig and Ulmann reactions, as well as a précis of some recent transition metal catalysed methods for C-H functionalisation of pyridines. It also reviews classical and transition metal catalysed methods for conjugate addition and Diels–Alder reactions of vinylpyridines. Chapter 2 involves reaction discovery for the use of Lewis acids for the activation of pyridines towards nucleophilic aromatic substitutions, reaction optimisations, kinetic investigations and an examination of the scope in substrates and incoming groups. Chapter 3 investigates the use of Lewis acids for the activation of vinylpyridines toward conjugate addition, reaction optimisations, investigations into scope of incoming groups and subsequent optimisation studies for each. The method is also extended to Diels–Alder cyclisations, for which the reaction is also optimised.
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Heavy atom induced phosphorescence of organic materials using mono- and trifunctional organomercury derivativesBurress, Charlotte Nicole 15 May 2009 (has links)
This dissertation focuses on the phosphorescence of organic chromophores using
perfluoro-ortho-phenylene mercury (1) and bis(pentafluorophenyl)mercury (2) as
external heavy atom effect inducers. To ascertain the suitability of these luminescent
adducts for OLED applications, several research objectives have been investigated.
To further shorten the triplet lifetimes of adducts involving 1, a strategy was
developed which combines both internal and external heavy atom effects. Specifically,
complexes involving 1 and N-methylcarbazole, N-methylindole and the 1-
halonaphthalenes were investigated. The existence and stability of the complexes could
be confirmed in solution by fluorescence spectroscopy. In the solid state, these adducts
form supramolecular binary stacks where the molecules of 1 alternate with the aromatic
substrate. As a result of the mercury external heavy atom effect, all of these adducts
display intense room temperature phosphorescence of the free arene. With the Nheterocycles,
the triplet lifetimes were drastically reduced to below 100 mu-s.
To appreciate the origin of the unusual heavy atom effects observed in arene
adducts with 1, 2 was studied as a monofunctional analog to 1. By utilizing fluorescence
spectroscopy, naphthalene, biphenyl, and fluorene complexes of 1 and 2 have been
detected in solution. The solid state structure of the adducts with 2 reveal
supramolecular binary stacks. Comparison of the photophysical results supports the
occurrence of cooperative effects between the Lewis acidic mercury centers of 1, which
make it a more efficient external heavy-atom effect inducer. Polymeric materials which are amenable to deposition in thin layers were
investigated as substrates for 1 and 2. Both poly(vinyl-2-naphthalene) and
poly(vinylcarbazole) interact with 1 and 2 in solution as evidenced by fluorescence
spectroscopy. With the solid blend 1•PVK, a small doping percentage of 1 results in
white emission, while larger percentages of 1 yield bright orange emission.
This dissertation presents the first structurally characterized ternary complex with
1, carbazole, and coordinating solvents THF and triethylamine. IR spectroscopy and
short N···O and N···N distances in the solid state indicates that the acidic N-H moiety of
carbazole interacts with the solvent by hydrogen bonding. In the extended structure,
molecules of 1 and the hydrogen bonded complex alternate to form supramolecules.
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Host-Guest Chemistry of Inorganic Porous PlatformsAlsufyani, Maryam 07 1900 (has links)
Complexes made by hosts that completely surround their guests provide a mean to stabilize reactive chemical intermediates, transfer biologically active cargo to a diseased cell, and construct molecular scale devices. By the virtue of inorganic host-guest self-assembly, the nucleation processes in the cavity of a {P8W48}-archetype phosphotungstate has afforded a nanoscale 16-GaIII-32-oxo cluster that contain the largest number of GaIII ions yet found in polyoxometalate chemistry. Catalytic activity via thus “Metal-Oxo Cluster within Cluster” Assembly has been preliminarily investigated. Besides, the hybrid aggregates composed of the inorganic {P8W48} and orgainc cyclic moiety has been studied.
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Connecting Synthesis-Structure Relationships in Zeolites to Establish High Performance Catalytic MaterialsSpanos, Alexander P. January 2022 (has links)
No description available.
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