Hemibiquinones: synthesis and computational validation of an asymmetric d—a biphenyl system

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dc.contributor Metzger, R. M.
dc.contributor Street, Shane C.
dc.contributor Szulczewski, Gregory J.
dc.contributor Leclair, Patrick R.
dc.contributor.advisor Woski, Stephen A.
dc.contributor.author Meany, Joseph E.
dc.date.accessioned 2017-04-26T14:26:02Z
dc.date.available 2017-04-26T14:26:02Z
dc.date.issued 2016
dc.identifier.other u0015_0000001_0002375
dc.identifier.other Meany_alatus_0004D_12861
dc.identifier.uri http://ir.ua.edu/handle/123456789/3095
dc.description Electronic Thesis or Dissertation
dc.description.abstract In order to help determine the governing characteristics behind asymmetric current flow in molecules (molecular rectification), it is important to establish size limitations for the electron transfer processes which make rectification possible. Here I present the rational design and synthesis of a molecular template which has been tested for its rectification properties, alongside important derivatives. The molecule template in question, hemibiquinone (HBQ), is an asymmetric biphenyl derivative composed of a dimethoxybenzene ring covalently bonded to a benzoquinone (2,5-cyclohexadiene-1,4-dione) ring. It contains a 2-position group allowing the molecule to self-assemble. Early recognition that the molecule already possessed electroactive donor (dimethoxybenzene) and acceptor (benzoquinone) sections led the author to hypothesize that the torsion angle between the rings of biphenyl is orbital isolating enough to be the requisite tunneling barrier necessary for unimolecular rectification. Spectroscopic and electrochemical data are presented to validate predictions made by Density Functional Theory. A monolayer of the molecule sandwiched between gold is found to rectify with a forward/reverse current ratio approaching 200. This result demonstrates that larger, saturated carbon bridges are not necessary components in the design of a molecular diode. Any way of breaking conjugation in the system will suffice. Beyond establishing a lower limit for D-σ-A rectifiers, this work also lays the foundation to experimentally test how properties such as polarity, torsion angle, end group effects and HOMO-LUMO gap energy affect the rectification efficiency for a given structure. Future work will focus on the systematic change of functionality to the hemibiquinone motif, and relating the measured conduction and rectification ratio to one another.
dc.format.extent 302 p.
dc.format.medium electronic
dc.format.mimetype application/pdf
dc.language English
dc.language.iso en_US
dc.publisher University of Alabama Libraries
dc.relation.ispartof The University of Alabama Electronic Theses and Dissertations
dc.relation.ispartof The University of Alabama Libraries Digital Collections
dc.relation.hasversion born digital
dc.rights All rights reserved by the author unless otherwise indicated.
dc.subject.other Chemistry
dc.subject.other Nanotechnology
dc.subject.other Materials Science
dc.title Hemibiquinones: synthesis and computational validation of an asymmetric d—a biphenyl system
dc.type thesis
dc.type text
etdms.degree.department University of Alabama. Dept. of Chemistry
etdms.degree.discipline Chemistry
etdms.degree.grantor The University of Alabama
etdms.degree.level doctoral
etdms.degree.name Ph.D.

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