A series of selectively fluorinated tolans of the general formulae C(_6)F(_5)-C=C-C(_6)H(_4)X and C(_6)H(_5)-C=C-C(_6)F(_4)X (where X = I, Br, CI) have been synthesized via homogeneous palladium-catalysed Sonogashira cross-coupling and organolithium chemistry. Several of their crystal structures have been solved from X-ray diffraction data, and their molecular packing is described in terms of arene-perfluoroarene and halogen-halogen interactions. Diffraction-quality crystals of a number of binary arene-perfluoroarene complexes of hexafluorobenzene and octafluoronaphthalene with several mismatched polyaromatic hydrocarbons have been obtained and their crystal structures solved from X-ray diffraction data. All of the structures have been shown to consist of infinite stacks of alternating components. The individual structures are compared and contrasted in detail, and those of the HFB complexes are found to closely resemble those predicted from ab initio DFT calculations, which implies that the interactions are over 90 % electrostatic in nature, in contrast with previous calculations on related complexes. A number of selectively fluorinated 4,4'-bis(phenylethynyl)tolan (BPET) derivatives containing fluorinated and non-fluorinated phenyl rings, have been synthesized from palladium-catalysed Sonogashira cross-coupling of various tolan-based precursors. They are observed to strongly absorb in the UV range 336 - 342nm, which are directly comparable to the absorptions for similarly fluorinated 1,4-bis(phenylethynyl)benzene derivatives which suggests that an effective conjugation length (ECL) of 3-4 repeat units is applicable for these phenylene ethynylene systems. They are observed to fluoresce very strongly in the range 372-410 nm. The diethynylbenzene derivatives 1,4-diethynyltetrafluorobenzene and 1,4- diethynyl-2,5-difluorobenzene have been synthesized from the hydrodesilation of their trimethylsilylated precursors. Their crystal structures have been solved from X-ray diffraction data, and are described in terms of C=C-H F and C=C-H π(C=C) interactions.

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Loline alkaloids (LA) are secondary metabolites produced by Epichloandamp;euml; (anamorph, Neotyphodium) grass endophytes. They are toxic and deterrent to a broad range of herbivorous insects but not to livestock. This protective bioactivity has spurred considerable research into the LA biosynthetic pathway. LOL, the gene cluster containing nine genes, is required for LA biosynthesis. The regulation of LOL genes during LA production in culture and in symbio is of interest. In this study, coordinate regulation between LOL gene expression and LA production level was investigated in both MM culture and symbiota. Results showed that expression of LOL genes in N. uncinatum MM culture were tightly correlated with each other (p andamp;lt; 0.0005), and all presented a significant temporal quadratic pattern during LA production. Gene expression started before LA were detectable, and increased while LA accumulated. The highest gene expression level was reached before the highest amounts of LA were detected, and gene expression level declined to a very low level after amounts of LA plateaued. Observations suggested that the hierarchical clusters based on the correlation coefficient could help to predict the roles of LOL genes in the LA pathway. In symbiota, coordinate coregulation of LOL gene expression with LA was found in E. festucae-meadow fescue inflorescences and stromata, whereby lower LOL gene expression corresponded with the lower LA level in stromata. In N. uncinatum (or N. siegelii)-meadow fescue vegetative tissues, dramatically higher LA levels were found in younger leaf tissue than in older leaf tissue, yet no evidence was found to relate this difference to LOL gene expression differences. Instead, substrate availability may regulate the LA level. In particular, asparagine was more than 10-fold higher in young leaf tissue than in old tissue, although proline was significantly lower in young tissue. Therefore, different regulatory mechanisms underlie LOL gene expression and LA production in different circumstances. The GUS activity of Pro-lolC2-GUS and Pro-lolA2-GUS in Neotyphodium species was almost undetectable in culture, though the activity could be detected in symbiota. The mRNA of GUS did not exhibit the same pattern as lolC2 or lolA2 in culture during LA production time course. A Pro-lolC2-cre transgene was expressed in complex medium, in which lolC2 mRNA was not detectable. These results suggest that proper regulation of LOL genes in culture or symbiota is dependent on the LOL cluster.

Fluoropolymers have useful properties including high thermal stability, chemical resistance, low dielectric constants, and both hydrophobic and oleophobic character, as compared to non-fluorinated analogues. Meanwhile, Diels-Alder polyphenylenes (DAPPs) are known for thermal stability as well as their rigid structure and glassy physical characteristics, which have led to a variety of film and membrane applications. This dissertation merges these two fields by demonstrating a novel and general synthetic approach to highly fluorinated DAPPs. These polymers are expected to retain the physical characteristics of glassy, non-fluorinated DAPPs while also incorporating the desirable attributes of fluoropolymers. The polymer synthesis described herein is based on the well-established polycondensation of bis(cyclopentadienone) (CPD) monomers and dialkynes. Our first main scientific contribution is a general method for preparing CPDs containing both a fluoroaromatic linker and variable fluoroaromatic head-groups. Our CPD synthesis uses nucleophilic aromatic substitution reactions of cyclopentadienyl anions and perfluoroarenes, as well as a new catalytic method of converting cyclopentadiene methylene (CH₂) groups into the corresponding ketones (C=O) that is the primary dissertation subject of Brian S. Hickory in our laboratory. The overall synthesis is notable for its use of inexpensive starting materials, its efficiency, and its structural versatility. Our second main contribution is the synthesis of novel highly fluorinated Diels-Alder polyphenylenes (DAPPs). Fluorinated DAPPs varied in their molecular weight, in the identity of the lateral fluoroaryl substituent (pentafluoro-phenyl or tetrafluoro-4-pyridyl), and in the structure of the aromatic dialkyne monomer. These polymers are glassy materials with high glass transition temperatures and high thermal stability. Since the polyphenylene structure is intrinsically rigid, the polymers form brittle films even at molecular weights of over 30,000 (M_w). Unlike many fluoropolymers, the fluorinated DAPPs are freely soluble in common organic solvents such as tetrahydrofuran and chloroform. An unknown side reaction competes with the polymer propagation and reduces the highest obtainable molecular weights, which limit the ability to form films. However, a stoichiometric imbalance leads to highly fluorinated polyphenylene oligomers terminated with either alkyne or CPD end groups (M_n = 9000). Because preliminary experiments had shown that the desired Diels-Alder propagation reaction was slower than expected, we also undertook a detailed model study of the reaction conditions needed for Diels-Alder reactions of fluorinated CPDs and aromatic alkynes. These experiments showed that protic polar solvents (e.g., m-cresol) and conventional heating at ca. 150 °C optimize reaction rate while minimizing side-reactions that can contribute to lower molecular weight in corresponding polymerization reactions. / Ph. D.