This thesis covers the synthesis, characterization and physical studies of cross-conjugated macrocycles, expanded radialenes, as well as their related derivatives. The main synthetic protocol that is used throughout this thesis is based on the Pd-mediated Sonogashira cross coupling reaction of a desilylated iso-polydiacetylene with a dibromoolefin. To initiate the synthesis, a series of [3], [4], and [5]expanded radialenes was synthesized, characterized, and studied by UV-vis spectroscopy, electrochemistry, and solid-state analysis. The results confirm the macrocycles are achievable in reasonable yields and suitable for further physical studies without any concerns for their stability in the solid or solution phase. At the same time, the use of tetrabromoethene in analogous Sonogashira cross coupling reactions afforded bisexpanded radialenes and radiaannulenes that exhibited interesting physical properties according to UV-vis spectroscopy and cyclic voltammetric analysis. This thesis also covers some interesting results, in particular, for [3]expanded radialenes that undergo cycloaddition reactions. As well, physical studies of the target radialenes show that as the macrocycles become more strained, they exhibit more unique and unexpected electronic and optical properties. Having the first series of the radialenes in hand, the synthetic plan shifted towards the synthesis of functional expanded radialenes, which were produced in good to very good yields. In particular, the existence of a [4]expanded radialene carrying triisopropylsilylethynyl groups as exocyclic substituents provided an opportunity for derivatization of the expanded radialene framework. The general protocol for radialene synthesis was also applied using tetrabromides of anthracenylidene and pentacenylidene in Sonogashira reactions. These efforts afforded structurally unique bisexpanded radialene and radiaannulene products. Because of their shape and structure, radialenes have potential for use in organometallic chemistry or as ligands in inorganic chemistry. Exploratory studies have been focused on [3] and [4]expanded radialenes. By all accounts, [3]radialenes reacted more easily with selected precursors such Pt(PPh3)4 and Co2(CO)8. Throughout this thesis, all the major radialene frameworks are established in terms of solid-state structures by X-ray crystallography. Finally, electrochemical analyses show that the new series radialenes reported in this work are generally reduced at higher potentials when compared to the previous generation of expanded radialenes based on butadiynyl building blocks.

A series of copolymers based on poly(phenylene thienylene) mainchain that contains pendent bisterpyridine ruthenium(II) complexes was synthesized by palladium catalyzed Suzuki coupling reaction. The polymers contain different proportion of metal complexes. The copolymers exhibit broad absorption band in the visible region due to the conjugated backbone and the bisterpyridine ruthenium complexes. The relative intensity of each absorption band depends on the metal complex contents. There is a significant spectral overlap between the emission of the conjugated polymer mainchain and the absorption of the ruthenium complexes. It was found that there is a quenching of polymer emission by the complexes. Based on the results obtained by spectroscopic studies, it is proposed to be Förster type energy transfer process between the polymer mainchain as the donor and the complexes as the acceptors. Two donor-acceptor molecules with pyrazinopyrazine bridge units were synthesized. They exhibit intramolecular charge transfer character and were characterized by 1 H NMR, FTIR, UV-visible absorption and mass spectrometry. The two compounds have absorption band in the near IR region and exhibit narrow band gap. Through structural modification, their optical and electronic properties can be fine tuned. They have potential applications in organic photovoltaic cells and organic field effect transistors. / published_or_final_version / Chemistry / Master / Master of Philosophy

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Thesis (Ph.D.)--Boston University / Carbon based n-conjugated materials, such as conducting polymers, fullerene, carbon nanotubes, graphene. and conjugated dendrimers have attracted wide scientific attentions in the past three decades. This work presents the first unified model Hamiltonian that can accurately capture the low-energy excitations among all these pi-conjugated systems, even with the presence of defects and heterogeneous sites. Two transferable physical parameters are incorporated into the Su-Schrieffer-Heeger Hamiltonian to model conducting polymers beyond polyacetylene: the parameter 1 scales the electronphonon coupling strength in aromatic rings and the other parameter e specifies the heterogeneous core charges. This generic Hamiltonian predicts the fundamental band gaps of polythiophene, polypyrrole, polyfuran, poly- (p-phenylene), poly-(p-phenylene vinylene), polyacenes, fullerene, carbon nanotubes, graphene, and graphene nanoribbons with an accuracy exceeding time-dependent density functional theory. Its computational costs for moderate-length polymer chains are more than eight orders of magnitude lower than first-principles approaches. The charge and energy transports along -conjugated backbones can be modeled on the adiabatic potential energy surface. The adiabatic minimum-energy path of a self-trapped topological soliton is computed for trans-polyacetylene. The frequently cited activation barrier via a ridge shift of the hyper-tangent order parameter overestimates its true value by 14 orders of magnitude. Self-trapped solitons migrate along the Goldstone mode direction with continuously adj usted amplitudes so that a small-width soliton expands and a large- width soliton shrinks when they move uphill. A soliton with the critical width may migrate without any amplitude modifications. In an open chain as solitons move from the chain center toward a chain edge, the minimum-energy path first follows a tilted washboard. Such a generic constrained Goldstone mode relaxation approach is applicable to the pinning dynamics due to the presence of structural defects and counter ions. The interchain 7r - 7r interactions are modeled using distance-dependent hopping integrals. Excellent agreements in their binding energetics and geometries with post-Hartree-Fock ab initio methods are found for the benzene dimer and the infinite 2D graphene cases. The computed photo-induced charge separated states and associated adsorption spectra agree perfectly with the experimental measurements.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 158-165).

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Poly (para-phenylenevinylene) (PPV), and its derivatives such as poly [2-methoxy, 5-(2'-ethyl-hexoxy)-1,4-phenylene vinylene] (MEH-PPV), are typical conjugated polymers. In order to implement conjugated polymers into processable electronics technologies, we must first understand their complex photophysical properties as their efficiencies depend on the balance between exciton recombination and charge carrier formation. The inherent complexities of these materials arise from entanglement of the pi-electron system with disorder and nuclear motions of the polymer backbone. This disorder breaks the polymer chain into conformational subunits which can couple, giving rise to a set of delocalized states formed by Coulombic interactions between proximate subunits. Characteristics of PPVs include high quantum yields, non-mirror image absorption and fluorescence line shapes, and large apparent Stokes' shifts. These properties are discussed in the context of the relationships between polymer conformation, electronic structure, coupling, disorder and polymer photophysics. These important influences are often manifest in the dynamics of what happens after photoexcitation. In this work, we present 3-pulse photon echo peak shift (3PEPS) studies of conjugated polymers in both solution and film. To elucidate timescales characteristic of relaxation processes, we have simulated the 3PEPS data simultaneously with absorption and fluorescence, observing a rapid localization of the exciton in the initial ~ 20 fs. Additional contributions to the decay of the peakshift are discussed. We also present transient anisotropy data for PPV polymers and oligomers which is compared to dynamics simulation for isolated chains of PPVs. This work demonstrates the influence of microscopic structure on ultrafast dynamics. We show that relaxation between exciton states can lead to rapid depolarization of the anisotropy, even though the spatial extent of exciton migration may be small. Generally, the connection between conformation and electronic structure is a theme throughout this thesis.

We hypothesized that subcutaneous (s.c.) adipose tissue would differ in monounsaturated (MUFA) and saturated fatty acid (SFA) composition among different depots throughout a beef carcass. To test this, 50 carcasses from a variety of breed types and backgrounds were sampled. External fat samples were collected from eight different carcass locations: round, sirloin, loin, rib, chuck, brisket, plate and flank. Samples were used to provide information on slip points, fatty acid composition and MUFA:SFA ratios. Lipids were extracted from s.c. adipose tissue by a modified chloroform:methanol procedure, and fatty acid composition and slip points were measured. The brisket was significantly lower in palmitic (16:0) and stearic (18:0) acid than the other seven sampling sites (P = 0.001). The brisket demonstrated the highest values of MUFA (P = 0.001) with the exception of possessing the lowest value of transvaccenic (18:1t11) acid (P = 0.002). There were also significant differences in the amounts of PUFA among the eight sampling sites. The lowest values were from the brisket with a mean of 25.1. The flank had the highest slip point with a mean of 39.0 (P ≤ 0.001). There was a high negative correlation shown between palmitoleic and stearic acid (R2 = 0.827). The brisket displayed the highest values for MUFA:SFA ratios (P = 0.001), whereas the flank was the lowest. Due to the significant differences amongst fat depots within bovine carcasses in their fatty acid composition we conclude that substantial differences exist across fat depots.