Abstract Not Available.

Abstract Not Available.

Abstract Not Available.

The ultimate objective of the work now to be described is the total synthesis of phyllocladene by a method which may at the same time provide some chemical evidence for configuration. Substantial progress towards this goal has been achieved.

Diazonium salts were first prepared by Griess in 1858 by the reaction of aromatic amines and nitrous acid. In a series of later publications he reported that phenols and aromatic halides are formed by the decomposition of these diazonium salts. However it was not until 1884 that Sandmeyer discovered the ability of cuprous salts to catalyze the conversion of diazonium salts to aryl chlorides and aryl bromides. Since this time this reaction, which bears his name, has been used in most of the preparative work involving the replacement of the diazonium group by these atoms. From the time of their discovery until the present time these reactions have been the object of the study of many organic chemists. The original purpose of this research project was to offer new evidence for the mechanism of these reactions.

Abstract Not Available.

New synthetic routes leading to 1-vinylcyclopropene and methylenecyclopropene were established making use of the Vacuum Gas-Solid Reaction (VGSR) technique. Both syntheses were planned in a way that allowed the use of solid fluoride as the dehalosilylation inducing reagent in the last step. The decomposition of methylenecyclopropene at temperatures above $-$75$\sp\circ$C was investigated and a dimer of methylenecyclopropene was proposed as the initial decomposition product. Fullerenes have been synthesized and separated using chromatographic techniques. Helium containing isomers of higher fullerenes were analyzed by $\sp3$He NMR spectroscopy and signals were assigned to isomers of C$\sb{76}$, C$\sb{78}$ and C$\sb{84}$. A novel C$\sb{60}$ derivative has been synthesized by the reaction of C$\sb{60}$ with cyclopropa (b) naphthalene and the product of the reaction with $\sp3$He@C$\sb{60}$ revealed the signal of the new compound in the $\sp3$He NMR. Fullerene hydrides $\sp3$He@C$\sb{60}$H$\sb{36}$ and $\sp3$He@C$\sb{60}$H$\sb{18}$ were synthesized by Birch reduction or reaction of $\sp3$He@C$\sb{60}$ with dihydroanthracene and the products were analyzed by $\sp3$He NMR. The spectra revealed one isomer for C$\sb{60}$H$\sb{18}$ and two isomers for C$\sb{60}$H$\sb{36}$. The most intense signal for C$\sb{60}$H$\sb{36}$ was assigned to the isomer with D$\sb{\rm 3d\sp\prime}$ symmetry based on the $\sp3$He NMR chemical shift value.

Isomers of the higher fullerenes were analyzed using 3He NMR spectroscopy. Structures have been assigned to isomers for C76, C78 and C84. Several fullerene hydrides, C60H n (n = 2, 4, 6, 8, 18, 36), have been synthesized using a novel hydrazine reduction. Other fullerene hydrides, C60Hn (n = 38, 40, 42, 48), were synthesized via the Birch reduction of the hydrazine reduction products. Seven of eight isomers for C60H4 have been observed in the proton NMR spectra. 3He NMR spectra were obtained for 3He C60H4, 3He C 60H18 and 3He C60H36. These spectra revealed six isomers for C60H4, one isomer for C60H18 and two isomers for C60H 36. The most intense signal in the 3He spectrum for C 60H36 was assigned to the isomer of D3d' symmetry based on the 3He NMR chemical shift value. High field proton NMR analyses (750 MHz) of C60H2 and C60H4 in 1:1 solutions of CS2:C 6D6 gave spectra with signals which showed unexpected additional fine structure as a result of an alignment effect caused by the orientation of benzene in a strong magnetic field.

"Nanocomponentry" is defined as a collection of nano-sized molecules or units that can be chemically assembled in various configurations to form structures intended to do work at the nanoscale. C60 fullerenes and carboranes are both spherically in shape and possess a variety of unique properties. Described here is the design, synthesis, and testing of molecules, with the emphasis on the use of C60 and carborane and their related chemistries, to help understand nanocomponentry. In chapter 1, in a continuation of the nanocar project (single molecular surface-rolling nanomachines comprised of spherical fullerene wheels, freely rotating alkynyl axles and a molecular chassis), a series of fullerene-based nanomachines were designed and synthesized to further our understanding of the directional control and surface-rolling capabilities of the series. Chapter 2, azobenzene moieties were studied to introduce a "handle" for photochemically controlled nanomachines and devices. The presence of fullerenes in the systems had an effect on the photoisomerization of the molecules. To observe the effects of the fullerenes, wheels produced from p-carboranes were introduced. In chapter 3, because of the advantageous properties, several nanovehicles were synthesized using p-carboranes as the wheel system. In chapter 4, the idea of an assembly line to produce nanovehicles is explored. In chapter 5, several imaging techniques were explored in order to address issues such as molecular resolution and substrate compatibility. In chapter 6, as an initial step toward exploring the transparency phenomena of the images of fullerene-functionalized devices and nanomachines from the past STM experimentation, a non-symmetric OPE was synthesized, where solublizing dodecyl groups were removed on one end of the OPE. In chapter 7, a series of fullerene-derivatized OPEs was synthesized for potential use in electronic devices. The products were terminated with thiols and protected thiol alligator clips to enable surface assembly on metallic surfaces such as gold. Throughout my career in the Tour group, I have been active in generating computer graphic images of my own projects as well as images for other projects within our group. In chapter 8 I present some of the notable illustrations I generated that were published in some form of media.

Understanding the rules of self-assembly in a large-scale biological structure is crucial to the design and fabrication of functional nanostructured materials. Substantial research efforts have made it possible to identify the elements that are important in stabilizing the highly complex quaternary structures of several proteins, including viral capsids, several types of intra and extracellular matrices and a group of disease-related polypeptides/proteins exhibiting a "cross-beta" sheet structure. This thesis describes the de novo design of synthetic mimetics of two protein motifs, alpha-helical coiled coils and amyloid beta-sheets and the parameters which control conversion between these two motifs. Chapter 1 reviews the current progress of self-assembled synthetic polypeptide based nanofibrous materials. Chapter 2 investigates the pH-dependent helical stability of de novo designed short coiled coil homodimers and heterodimers. Chapter 3 discusses the general problem of the lateral aggregation seen in most of the coiled coil based nanofiber systems. In addition, the concentration-dependent fiber formation has been generalized as an intrinsic property of peptides with similar primary sequences. In chapter 4, the dynamic secondary structure of coiled coil-sequenced peptides has been extensively studied using a variety of biophysical methods including CD, ATR FT-IR, grazing angle FT-IR, TEM, cryo-TEM, and AUC. The secondary structure helix-sheet transition with the commensurate amyloid formation was found to be associated with the presence of the hydrophobic clusters in the central region of the primary sequence, which leads to the aggregation of the individual beta-sheet into a sandwich-like assembly. In chapter 5, utilizing the understanding of hydrophobic clusters gained in chapter 4, a new class of fiber-forming multidomain peptide (MDP) was developed with an alternating pattern of hydrophobic and hydrophilic residues. Controlled nanostructural morphology, in this case soluble nanofibers with controlled length, was achieved by varying the ratio of the central repeating number of (Gln-Leu) and the flanking charged lysine residues. Finally, chapter 6 discusses the application of the MDP in 3-D cell culture as an extracellular matrix mimetics. The attachment of short peptide sequences (RGDS and PHSRN) was found to dramatically enhance the cell proliferation rate. The fact that the biological active motifs can be specifically recognized on these peptide-based scaffolds will encourage further investigation of attaching diverse biologically functional constructs on these peptide matrices for specific tissue repair and regeneration.