Donor-Sigma-Acceptor (D-sigma-A) Molecules With Perylenebisimide Acceptors Having Alkyl or Peg Swallowtails With Sulfur or Hydroxyl Anchors: Synthesis and Applications in Langmuir-Blodgett Films, Single Molecule Spectroscopy (SMS), G-Quadruplex Studies and Passivation of Gold Nanoparticles
Use of single molecules as electronic devices is presently considered a potential alternative to semiconductor-based nanoscale electronics. The ability to study a single molecule or a small group of molecules provides a great opportunity to build electronic devices at the molecular level. It is vital to understand the parameters that control the device properties such as molecular structure, conformation and arrangement at the surface. Ari Aviram and Mark A. Ratner proposed the construction of a single organic molecule as an organic rectifier. Donor-Sigma-Acceptor (D-?-A ) molecules, when arranged with a proper orientation as Langmuir-Blodgett (LB) films and fixed between two electrodes, act as one-electron organic rectifiers (allowing the passage of current in one direction). In this work perylenetetracarboxylic bisanhydride is used as the acceptor. Perylenetetracarboxylic bisanhydride derivatives are very intractable (insoluble in all regular solvents). Attaching a swallowtail (alkyl or PEG) improves their solubility and helps in making a well-ordered LB monolayer. The project includes multistep syntheses of D-?-A molecules with alkyl swallowtails containing sulfur anchors (to induce stability to the LB monolayers and to make self assembled monolayers) and/or PEG swallowtails, with or without hydroxyl end groups (to investigate the orientation of the LB films). The alkyl swallowtail project includes making alkyl swallowtail amines with sulfur anchors and proceeding through a crucial perylene monoanhydride monoimide intermediate with two thioacetyl groups, using two different routes starting from 11-bromoundecanoic acid or undecylenic acid. These schemes include Fischer esterification, Claisen condensation, decarboxylation, reductive amination and radical thioester addition as key reactions. The PEG swallowtail project includes making PEG swallowtail amines with hydroxyl, chloro or sulfur end groups. These amines were made from 2-amino-1,3-propanediol and either hydroxyl or chloro tosylates. This scheme includes amine protection, Williamson ether synthesis and simultaneous imidization as key reactions. A dozen different swallowtail amines were attached to the perylenetetracarboxylic acceptor by imidization to make unsymmetrical perylene bisimides (PBI 's). Several donors, with different ionization energies, have been prepared and were coupled to perylenetetracarboxylic imide anhydrides to prepare the final D-?-A molecules. The dependence of the orientation of these molecules as LB films on the nature of swallowtail (PEG swallowtail, lipid thioacetate anchored swallowtail) was studied by pressure area ( II-A) isotherms and contact angle measurements. In addition to the application of the D-?-A molecules in Langmuir-Blodgett films, we found various applications of these molecules in single molecule spectroscopy (SMS), DNA binding studies to stabilize G-quadruplex, and passivation of gold nanoparticles.
Donor-Sigma-Acceptor, G-Quadruplex, Molecular Electronics, Organic Chemistry
Networked Digital Library of Theses and Dissertations