published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

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Thesis advisor: Lawrence T. Scott / The distinctive molecular structure of carbon nanotubes makes them desirable for electronic and chemical materials; however, current production methods are limited with respect to purity and chirality. Geodesic polyarenes serve as superb templates for the bottom up synthesis of carbon nanotube end-caps, setting the chirality and dimensions of the carbon nanotubes. The work herein describes the synthetic efforts towards the rational synthesis of a [6,6] carbon nanotube end-cap. Chapter 1 describes the efforts towards the synthesis of a C60H12 end-cap, in which the synthesis of an advanced intermediate, peri-bis(dibenzo[a,g]corannulene) is complete; however, the insolubility of this material proved to be problematic in a subsequent cycloaddition reaction. This reaction is examined computationally in order to understand the failure of the addition of dienophile, maleic anhydride, to peri-bis(dibenzo[a,g]corannulene). In Chapters 2 and 3, the development of solubility-enhancing methods is described. The development of a solubility-enhancing dienophile is successfully employed to induce the solubility of a formerly insoluble diene, peri-bis(dibenzo[a,g]corannulene), through Diels-Alder addition. Another method, employs the incorporation of tert-butyl groups onto peri-bis(dibenzo[a,g]corannulene) to successfully induce solubility. The enhanced-solubility enables the successful Diels-Alder addition of simple maleimide dienophiles, installing all necessary carbon atoms for the desired end-cap. Pyrolysis of the bis-anhydride derived from the aromatized bis-maleimide adduct afforded the C60H12 end-cap, which is the second carbon nanotube end-cap ever synthesized and the first of these dimensions. Chapter 3 also explores a palladium catalyzed intramolecular arylation reaction to form a pivotal intermediate in the synthesis of the end-cap, dibenzo[a,g]corannulene. The mechanism for the formation of a problematic byproduct resulting from reductive dehalogenation is discussed. Utilizing a deuterium labeled solvent, it is found that deuterium is incorporated onto the hydrocarbon, indicating that the solvent (N,N-dimethylformamide-d7) is the source of hydrogen for the reductive dehalogenation. These conditions are further exploited in Chapter 4 for the convenient perdeuteration of a variety of polycyclic aromatic hydrocarbons. Chapter 5 describes the first synthesis of a nitrogen containing geodesic polyarene, dibenzo[g,m]azacorannulene. This synthesis is completed in seven steps from a commercially available source in a 28% overall yield. / Thesis (PhD) — Boston College, 2012. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

The research presented in this thesis deals with the synthesis, optical and photochemical studies of various porphyrin and/or fullerene based systems. The second chapter deals with the study of fullerene based molecules composed of C60 covalently linked to ferrocene and various nitroaromatic entities. Chapter three involves the study of molecules composed of zinc porphyrin covalently linked with ferrocene(s) self-assembled into supramolecular triads by axial ligation of imidazole bearing fulleropyrrolidine. The triad studied in Chapter four is composed of zinc porphyrin covalently linked to boron-dipyrrin which was selfassembled into a supramolecular complex by axial ligation of imidazole appended fulleropyrrolidine. Chapter five deals with the formation of a dyad complex composed of Zinc N-confused porphyrin axially coordinated to imidazole bearing fulleropyrrolidine. The compounds discussed in this thesis were studied by optical absorbance and emission, electrochemical, and time-resolved photochemical methods. These compounds were mainly characterized by 1H NMR, UV-vis absorbance, and ESI-mass. Binding constants for the supramolecular complexes were arrived using UV-vis spectroscopic methods. Also, B3LYP/3-21G(*) computational method was used to probe the geometric and electronic structure of the compounds studied. The triads studied in Chapter two revealed efficient photoinduced chargeseparation. Interestingly, the computed site of electron transfer using DFT methods was found to track the electrochemical results observed in the cyclic voltammetric experiments. The self-assembled triads in Chapter three revealed efficient charge-separation from the excited zinc porphyrin to the fullerene (C60) entity. Also, the triads revealed efficient charge stabilization due to the presence of ferrocene(s). The self-assembled triad in Chapter four revealed efficient energy transfer from the boron-dipyrrin entity to zinc porphyrin. The selfassembled triad exhibited energy transfer followed by electron transfer to the fullerene (C60) entity. In Chapter five the construction of a dyad composed of zinc N-confused porphyrin and fullerene (C60) was confirmed. Spectro- and photochemical experiments revealed efficient electron transfer from the porphyrin to the fullerene entity. / Thesis (Ph.D.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Chemistry. / "May 2006." / Includes bibliographic references (leaves 147-155).

The research reported in this thesis details the synthesis, characterization, electrochemical and photochemical studies of noncovalently linked porphyrin-fullerene based donor-acceptor systems. The first chapter gives an introduction that briefly summarizes the significant events that occur in natural photosynthetic systems, the importance of artificial photosynthetic models and finally, lists new developments in model biomimetic systems of this type. The second chapter discusses synthesis of control compounds and physical methods used in later chapters. The third chapter focuses on the investigation of covalently linked porphyrin-fullerene dyads. A discussion of the role of axially ligated pyridine in decreasing charge recombination rates can also be found in this chapter. The main investigations in the fourth chapter utilize noncovalently linked porphyrin-fullerene triads with two axial coordination bonds with an emphasis on the importance of structural rigidity and the orientation of the donoracceptor entities. The fifth chapter discusses the purpose of a secondary donor and the effect it has in charge separation and charge recombination rates for self assembled supramolecular triads formed via "two-point" binding. Noncovalently linked magnesium porphyrin-fullerene dyads and triads are presented in chapter six. The compounds contained in this thesis were synthesized and characterized by proton NMR and ESI-Mass spectroscopy. Binding constants were obtained by using UV-visible, fluorescence and 1H NMR spectral data. DFT calculations were performed to gain insight into the structural aspects and orientation of the donor-acceptor groups in these supramolecular complexes. Electrochemical and emissions studies (i.e. steady state and time resolved fluorescence, transient absorption) were employed to obtain free energy changes for electron transfer, lifetimes, charge separation and charge recombination rates for photo - induced electron transfer. / Thesis (Ph.D.)--Wichita State University, College of Arts and Sciences, Dept. of Chemistry. / Includes bibliographic references (leaves 189-199). / "May 2006."

Fullerenes, the highly symmetric molecular carbon clusters, have been in the limelight of scientific research since their discovery by Kroto and coworkers [1]. The focus of experimental and theoretical studies has centered on C60 and, to a lesser extent, on C70. A few larger counterparts have also been characterized [2]. It is generally believed that the cage compounds with adjacent pentagons are unstable (the so-called 'isolated pentagon rule': IPR) [3]. The smallest possible fullerene which satisfies the IPR is C60. Fullerenes smaller than C60 will necessarily have pentagons fused side by side and hence they are predicted to be unstable. While violations of the isolated pentagon rule have been suggested [4], the inability to achieve macroscopic synthesis of smaller fullerenes seemed to be in accord with their predicted instability. In a dramatic development, Zettl and coworkers [5] reported the synthesis and purification of C36. Their achievement led to increased activity in elucidating the properties of C36, both experimentally and theoretically.

Thesis (Ph.D)--Civil and Environmental Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Pennell, Kurt; Committee Member: Hughes, Joseph; Committee Member: Kim, Jaehong; Committee Member: Snyder, Robert; Committee Member: Yiacoumi, Sotira. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references. Also available in electronic version. Access restricted to campus users.

published_or_final_version / abstract / toc / Physics / Doctoral / Doctor of Philosophy

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