Browsing by Subject "Perylene"
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Item Characterization of low density oxide surface sites using fluorescent probes(2013-12) McCrate, Joseph Michael; Ekerdt, John G.Low density surface sites are believed to play an important role in processes occurring on oxide surfaces, including catalysis and particle and film nucleation. However, our understanding of the role and chemical nature of such sites play in these processes is limited by the inability to experimentally detect minority surface sites in many oxide systems. The research performed for this dissertation is focused on developing a surface science technique utilizing fluorescent molecules to titrate specific surface sites on planar fused silica surfaces in an ultra-high vacuum (UHV) environment. High sensitivity (low detection limit) is achieved by using derivatives of perylene, a high quantum yield fluorophore. High specificity is attained by employing perylene derivatives with functional groups designed to react chemically with and titrate various sites. In addition to titrating the well-studied hydroxyl sites with perylene-3-methanol (density ~ 10¹⁴ cm⁻²), which is used to establish the technique, the detection of strained siloxane sites (~ 10¹² cm⁻²), ) with perylene-3-methanamine and oxygen vacancy sites (~ 10¹¹ cm⁻²), ) with 3-vinyl perylene is demonstrated. Particle nucleation on oxides is suspected to involve defects that trap adatoms and form critical nuclei. Using this technique, the possible role strained siloxane and oxygen vacancy sites play in trapping adatoms during the nucleation of Ge nanoparticles on silica surfaces is examined.Item Photophysics of perylene diimides in solutions and self-assembled films(2006) Tang, Tingji; Bout, David A. VandenItem Synthesis and biological evaluation of 2-(2'-hydroxyphenyl) benzoxazole analogs of UK-1 and G-quadruplex selectivity of perylene diimide compounds: /(2007-12) McKee, Mireya Loreley, 1978-; Kerwin, Sean M.A great number of pharmaceutical drugs target nucleic acids. However, drug-DNA interactions can be region non-specific and lead to undesired side effects. Understanding the mechanisms that regulate drug-DNA binding can help in the design of potent and selective therapeutic agents with fewer deleterious side effects. The present investigation explores the metal-mediated DNA binding of a group of 2-(2-hydroxyphenyl)benzoxazole (HPB) ligands and the aggregation dependant G-quadruplex selectivity of a series of perylene tetracarboxylic acid diimides (PTCDI) compounds. HPB ligands are simplified analogs of the bis-benzoxazole natural product UK-1. This compound is able to inhibit cell growth of various tumor cell lines, bind divalent cations, and interact with DNA in a metal dependant fashion. The HPB moiety present in UK-1 was identified as relevant for its metal ion binding and biological properties. For this work, novel HPB ligands were synthesized with different substitutions at the C4 or C7 position. Their ability to bind metal ions and DNA was evaluated and their cytotoxicity was assessed in multiple cancer cell lines. The ligands bound to Cu²⁺ with the highest affinity among metals studied. Consequently, Cu²⁺ promoted the most dramatic increase in DNA binding and affected the ligand's cellular cytotoxicity. The second project focused on targeting four-stranded structures called G-quadruplexes, which can form in G-rich nucleic acid sequences. Compounds that stabilize these structures may inhibit nucleic acid-processing enzymes such as telomerase and potentially act as anti-cancer agents. PIPER is a PTCDI that is particularly selective for G-quadruplex DNA versus duplex DNA under conditions in which it forms aggregates. This work investigated ligand aggregation in a series of PIPER analogs with different structural features under high and low salt buffers, changes in pH, metal binding and temperature changes. A negatively charged analog was determined to form metal-mediated aggregates while novel thermophilic mediated aggregation was discovered for an analog with methoxyethoxymethyl groups. The ability of these ligands to bind different DNA structures was evaluated under aggregating and non-aggregating conditions. This study supports the idea that ligand aggregation increases their quadruplex selectivity and decreases double-stranded DNA binding.Item Synthesis and characterization of functionalized norbornene monomers and their resulting ring-opening metathesis polymers and copolymers(2011-12) Biberdorf, Joshua David; Holliday, Bradley J.; Humphrey, Simon M.The work reported herein describes efforts to create ring-opening metathesis block copolymers and homopolymers. The block copolymers were studied to gain insight into the local nanoscale environment of a block copolymer thin film. Additionally, perylene containing homopolymers were characterized in light of their possible use as an n-type material. In the first section of the thesis, the synthesis of diblock copolymers consisting of two blocks with very different dynamics is described. The covalent attachment of a molecular rotor which is sensitive to its local environment allowed the study of the dynamics of the polymers in thin films. The emissive intensity as a function of temperature allowed us to see discontinuity in the rates of change, indicating a change in the local environment corresponding to the transition of the polymer from a glassy to rubbery state. The corresponding temperature, to this event, is known as the glass transition temperature, Tg. Additionally, a polymer featuring a covalently bound n-type molecule, perylene diimide, was synthesized. The photophysical properties, including aggregation in dilute solution, are described. The material is expected to demonstrate the ability to efficiently transport negative charge, acting as n-type material in organic electronics.