This study has focused on the design and preparation of bi– and tridentate N–Heterocyclic Carbene (NHC) ligands in order to investigate the effect of a multidentate approach to the formation, stability and catalytic activity of coordination complexes. Chapters 1 – 3 provide background information of relevant catalysis, carbene and coordination chemistry, followed by previous work performed within our research group. In Chapter 4 attention is given to the synthetic aspects of the research conducted, comprising two distinct approaches to the preparation of unsymmetrical saturated and unsaturated NHCs. Firstly, an investigation of the saturated NHC ligands yielded three novel, unsymmetrical pro–ligands, viz., two halopropyl imidazolinium salts and a bidentate hydroxypropyl imidazolinium salt. Secondly, eight imidazolium salts have been generated, including a hydroxypropyl analogue and novel decyl and tridentate malonyl derivatives. These compounds were prepared using microwave–assisted methodology for the alkylation of N– mesitylimidazole – an approach that drastically reduced reaction times (from 8 hours – 7 days to ca. 0.5 – 2 hours) and facilitated isolation of the imidazolium salts. Many of the compounds prepared in this study are novel and were fully characterized using HRMS and 1– and 2–D NMR analysis. Coordination studies using a selection of the prepared pro–ligands afforded an alkoxy–NHC silver derivative and four novel Ru–complexes, viz., Grubbs II–type Ru–complexes containing:– chloropropyl imidazolinylidene; propenyl imidazolylidene; and bidentate alkoxypropyl imidazolylidene ligands. Furthermore, a well–defined benzyl mesitylimidazolylidene Ru–complex has been isolated, which exhibited good stability in air. DFT–level geometry–optimization studies, using the Accelrys DMol3 package have given valuable insights into the likely geometries of the prepared and putative catalysts.

This organometallic study involves the use organostannanes and organolithiums as precursors to chromium Fischer carbene complexes. Fischer carbenes are typically electrophilic and are stabilized by a single π-donor substituent, and contain low oxidation state metals (often but not always from Group 6). They are highly reactive and can give access to a range of biologically active compounds through cyclopropanations, insertions, coupling and photochemical reactions. Synthesis and characterization of three MOM-protected α-alkoxy organostannanes was successfully carried out via a nucleophilic addition of tributylstannyllithium to suitable aldehydes, and immediate protection of the alcohol with MOM. Two N-BOC protected α-amino organostannanes were successfully synthesized and characterized via α-lithiation and tin-lithium exchange in the presence of TMEDA. Tin-lithium transmetallation of the organostannanes allowed access to the organolithiums required for the synthesis of novel Fischer carbenes. Addition of chromium hexacarbonyl to the organolithiums formed the acylpentacarbonyl chromate salt which was alkylated with Meerwein salt, resulting in the Fischer carbene and a by-product, tetrabutyltin, which proved difficult to remove. Several Fischer carbenes were synthesized and characterized, some simple and known and some novel. In silico work explored the reaction coordinate of the [2+2] cycloaddition towards the formation of β-lactams, and the photoactivation cycle that precedes this process. Computational work also showed the effect of the ligand on the stability and reactivity of the carbene. It was found that in some cases the oxygen on the ligand could negatively influence the stability of the carbene (when compared to a simple methyl carbene). A link between bond orders and back donation in Fischer carbenes was explored in an attempt to theoretically predict the stability of a range of carbenes. / Microsoft� Office Word 2007

A computational chemistry analysis combined with a crystallographic database study of the bonding in late transition metal N-heterocyclic carbene (NHC) complexes is reported. The results illustrate a metal-carbon bond for these complexes, approximately 4% shorter than that of a M-C single bond found in metal alkyl complexes. As a consequence of this result, two hypotheses are investigated. The first hypothesis explores the possibility of multiple-bond character in the metal-carbon linkage of the NHC complex, and the second, considers the change in the hybridization of the carbenoid carbon to incorporate more p character. The latter hypothesis is supported by the results. Analysis of these complexes using the natural bond orbital method evinces NHC ligands possessing trans influence.

This dissertation summarizes my research in the Nuckolls group on two projects, with a central theme of achieving control of electronic coupling in various nanoscale systems. The two studies of interest aim at the study of emerging properties from alkali-doping of polyaromatic hydrocarbons (PAH), and the synthesis of novel metal chalcogen molecular clusters. Chapter 1 is divided into two parts. Part one provides a brief history of the forces we associate with bond formation. We will learn that although defining a “chemical bond” is helpful, it is limited to our incomplete understanding of what forces contribute to its existence. The behavior of an electron in externally applied magnetic fields will be discussed, where the collective behavior of electrons in a material can be measured, showing a myriad of emerging properties. The known superconducting alkali-doped PAHs are introduced, followed by the unresolved problems of reproducibility and lack of structural data to accompany superconducting samples. Finally, the proximity of AFM to superconductivity is discussed, which could give us insights on further exploration of hight temperature organic superconductors. Part two introduces atomically precise clusters of atoms, also knows as superatoms. Various synthetic approaches to create metal chalcogenide superatoms are introduced. Next, a closer look into the cobalt selenide core, [Co6Se8], is presented. The ability to selectively substitute the ligands on this superatom, achieves dimensional control. The subunit can be seen as a 0-dimensional subunit, where it readily gives away its electrons. Furthermore, assembly of the clusters into 1-, 2-, and 3-dimensional structures is described. Chapter 2 introduces a novel approach to acquire phase pure alkali-doped PAHs, p-terphenyl specifically. Previous reports of solution-processed doping of PAH have inspired highly reliable synthesis of these salts, by employing a chelating agent to stabilize the alkali metal. The first half of chapter 2 analyzes one such crystal in detail, describing emerging AFM fluctuations. The AFM coupling between nearest neighboring p-terphenyls occurs in all three crystallographic directions. Interestingly, this coupling can be seen as an unconventional bond between two terphenyl units along the hard axis, and resembles resonance structures seen in polyacetylene. The second half of the chapter further investigates the novel method, obtaining a library of alkali-doped p-terphenyls. This approach allows for selective variation of either the alkali-metal, the chelating agent, or the electronic structure of p-terphenyl. Obtaining nearly a dozen structures allows for a study of trends of doping level and accompanied magnetic properties. Lastly, Chapter 3 proves a new mechanism for ligand substitution of cobalt selenide superatomic clusters, using an easily removable carbene as the ligand. This approach grants access to new surface ligands and core shapes to expand the properties of these superatoms. Through this approach, larger atomically precise materials can be targeted, giving rise to new types of electronic properties.

Surfactants are surface-active agents decreasing surface tension to simplify removing dirt. Surfactants can be divided into four basic classes: anionic, cationic, non-ionic and amfolytic. In Czech Republic there are mostly used anionic surfactants nowadays which get into waste water through detergents. The thesis deals with the spectrophotometric determination of anionic surfactants and the study of interferences to this method.

Organometallic catalysis has attracted significant interest from both industry and academia due to its wide applications in organic synthetic transformations. Example of such transformations include the reaction of a zinc carbenoid with olefins to form cyclopropanes. The first project is a computational study using both density functional and correlated wavefunction methods of the reaction between ethylene and model zinc carbenoid, nitrenoid and oxenoid complexes (L-Zn-E-X, E = CH2, NH or O, L = X = I or Cl). It was shown that cyclopropanation of ethylene with IZnCH2I and aziridination of ethylene with IZnNHI proceed via a single-step mechanism with an asynchronous transition state. The reaction barrier for the aziridination with IZnNHI is lower than that of cyclopropanation. Changing the leaving group of IZnNHI from I to Cl, changes the mechanism of the aziridination reaction to a two-step pathway. The calculation results from the epoxidation with IZnOI and ClZnOCl oxenoids suggest a two-step mechanism for both oxenoids. Another important example of organometallic catalysis is the formation of alkyl arenes from arenes and olefins using transition metal catalysis (olefin hydroarylation). We studied with DFT methods the mechanism of a novel Rh catalyst (FlDAB)Rh(TFA)(η2–C2H4) [FlDAB = N,N’ -bis(pentafluorophenyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene; TFA = trifluoroacetate] that converts benzene, ethylene and air-recyclable Cu(II) oxidants to styrene. Possible mechanisms are discussed.

In the last two decades, significant strides have been made towards utilizing the scanning tunneling microscope (STM) as a reaction chemistry tool, in addition to its primary use as an imaging instrument. Built off the STM, the STM-break junction (STM-BJ) technique was developed specifically for the reliable and reproducible measurement of properties of a single molecule suspended between two electrodes. These advances are crucial to the fields of molecular electronics and single-molecule reactivity, the latter also relating back to traditional bulk chemistry. By intelligently designing experiments and systems to probe with the STM and STM-BJ, we can begin to understand chemical processes on a deeper level than ever before. Chapter 1 provides an overview of the recent work using the STM and STM-BJ to effect chemical transformations which involve the making and breaking of bonds. We contextualize this progress in terms of single-molecule manipulation and synthetic chemistry, to understand the implications and outlook of this field of study. Seminal surface-based reactions are discussed, in addition to reactions that occur in both solution and within the single molecule junction. Differences between STM and STM-BJ capabilities and limitations are detailed, and the challenges of translating these fundamental experiments into functional reactions are addressed. Chapter 2 describes using the STM-BJ to study the binding of aryl iodides between gold electrodes. Important details regarding these binding modes, which were previously incompletely understood, are revealed via concrete experimental evidence. Our data suggests that this system, which is synthetically accessible, holds promise for forming the sought-after and highly conducting covalent gold-carbon bonds in situ and can be modulated with applied bias. Chapter 3 builds upon the knowledge gained in Chapter 2, and focuses on the reactivity of aryl iodides in the junction. We demonstrate a new in situ reaction of an Ullmann coupling, or dimerization, of various biphenyl iodides. By strategically designing the molecules studied, we are also able to gain mechanistic insight into this process, which in the bulk still remains debated, as well as demonstrate a cross-coupling reaction. This project is ongoing as of the submission of this dissertation, so other findings and continuing experiments are included. Chapter 4 transitions towards a different type of binder to gold, the cyclopropenylidene-based carbene. These amino-functionalized carbenes prove to be stronger linkers than N-heterocyclic carbenes, which are known binders to gold. Using a variety of surface analysis, imaging, and computational techniques, we explore the binding geometries and energies of cyclopropenylidenes, expanding the scope of carbene surface modifiers. Chapter 5 summarizes this body of PhD research, suggests directions for future work, and concludes the dissertation. These works explore the binding and reactivity of molecules on gold surfaces and within the single molecule junction, improving upon the understanding of this newly burgeoning field. This thesis seeks to encourage future work on these and related systems, to continue refining our comprehension of both junction and bulk reaction chemistry processes.

In this study, a series of denim fiberboards are fabricated using two different resins, malamine urea formaldehyde (MUF) and polymeric methylene diphenyl diisocyanate (pMDI). Two experimental design factors (1) adhesive content and (2) MUF-pMDI weight ratio, were studied. All the denim fiberboard samples were fabricated following the same resin blending, cold-press and hot-press procedures. The physical and mechanical tests were conducted on the fiberboard following the procedures described in ASTM D1037 to obtain such as modulus of elasticity (MOE), modulus of rupture (MOR), internal bond (IB), thickness swell (TS), and water absorption (WA). The results indicated that the MOE was significantly affected by both factors. IB was affected significantly by weight ratio of different glue types, with 17 wt% more MDI resin portion in the core layer of the denim boards, the IB for total adhesive content 15% fiberboard was enhanced by 306%, while for total adhesive content 25% fiberboard, enhanced by 205%. TS and WA, with higher adhesive content used in denim boards' fabrication, and more pMDI portion in the core layer of the boards, the boards' TS and WA was reduced by up to 64.2% and 78.8%, respectively.

4’ -ester analogues of resveratrol were synthesized using reaction conditions developed to produce mono-ester products in the presence of two other unprotected phenols. Basic conditions were employed to deprotonate the most acidic 4’ phenol followed by addition of anhydrides or acid chlorides to give the ester product. The reaction favored 4’-ester formation in polar aprotic solvents with DMSO being the optimal solvent. (—)-Englerin A is a guaiane-type sesquiterpene containing two ester side chains. Mimics of (—)-englerin A were proposed that retained the ester side chains while replacing the non-polar core with less complicated structures. These proposed mimic cores would maintain the three-dimensional positioning of the esters which are responsible for the anti-cancer activity of (—)-englerin A. Three mimics were synthesized using the bicyclic terpenes borneol and fenchol. Installation of the second ester on the terpene core was accomplished throught the development and optimization of a unique methylene oxidation using chromium trioxide in glacial acetic acid. These mimics were screened against two kidney cancer cell lines. The compounds were shown to have IC50 (inhibitory concentration for 50 % of cells) values above 30 µM.

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