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EXTERNAL CONTROL OF ORTHO-PHENYLENE FOLDING

Vemuri, Gopi Nath
http://orcid.org/0000-0003-3022-8009
http://rave.ohiolink.edu/etdc/view?acc_num=miami1563204221995637

Abstract Details

2019, Doctor of Philosophy, Miami University, Chemistry and Biochemistry.
Foldamers are synthetic organic oligomers/polymers, inspired by the structures and functions of biomolecules, that adopt predictable and well-defined secondary structures stabilized by noncovalent interactions. These structures are strongly influenced by exterior functionalization and external surroundings such as the solvent. Studying these factors could allow control over oligomer folding, allowing the generation of new structures complementary to biopolymers. ortho-Phenylenes are a class of aromatic foldamers that fold into helices. Their folding is controlled by arene-arene stacking interactions parallel to their helical axes. This dissertation discusses how their folding behavior is affected by the surrounding solvent polarity, covalently connected terminal chiral groups and external functionalization with fluoro groups. Solvent polarity plays a major role in stabilizing structural conformations in most of the aromatic foldamer systems. Chapter 2 presents a detailed investigation of the folding behavior of o-phenylenes oligomers in different solvents with varying polarities. A clear trend has been observed in these systems: misfolded conformations are stabilized in polar solvents. These misfolded conformers are found to be more polar than the perfectly folded conformation. Chapter 3 examines structure-property relationships on the folding of o-phenylene hexamers with various chiral groups substituted at their termini through imine functionalization. Terminal substitution with point chirality biases the helical twist sense in these oligomers producing a mixture of different populations of right- and left-handed helices. However, the proximity of the chiral center has a huge impact on the effectiveness of chiral induction. In addition, the position and sterics of the groups around the asymmetric carbon relative to the helix determine the effectiveness of twist sense biasing. The terminal chiral groups in these systems are found to be “ambidextrous”, inducing opposite handedness depending on their arrangement in space with respect to the backbone. Chapter 4 looks into the simplification of o-phenylene exteriors with a chemically robust substituent. Functionalization of each phenylene ring in o-phenylene oligomers with moderately electron-withdrawing fluoro groups favors the perfectly folded conformation. Additionally, the 19F nucleus serves as a spectroscopic handle in studying different folding states present in the solution using 19F NMR. This strategy is extremely helpful in studying the folding behavior of longer o-phenylenes as well as more-complex structures derived from them.
Scott Hartley, Prof. (Advisor)
Dominik Konkolewicz, Prof. (Committee Chair)
Benjamin Gung, Prof. (Committee Member)
Rick Page, Prof. (Committee Member)
Andrew Paluch, Prof. (Committee Member)
234 p.
Organic Chemistry; Physical Chemistry
Organic chemistry, physical organic chemistry, foldamers, aromatic foldamers, phenylenes, ortho-phenylenes, o-phenylenes, solvent effects, solvent role on folding, chiral induction in foldamers, twist-sense biasing, helical handedness, 19F NMR

Recommended Citations

Citations

  • Vemuri, G. N. (2019). EXTERNAL CONTROL OF ORTHO-PHENYLENE FOLDING [Doctoral dissertation, Miami University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=miami1563204221995637

    APA Style (7th edition)

  • Vemuri, Gopi Nath. EXTERNAL CONTROL OF ORTHO-PHENYLENE FOLDING. 2019. Miami University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=miami1563204221995637.

    MLA Style (8th edition)

  • Vemuri, Gopi Nath. "EXTERNAL CONTROL OF ORTHO-PHENYLENE FOLDING." Doctoral dissertation, Miami University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=miami1563204221995637

    Chicago Manual of Style (17th edition)

miami1563204221995637
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© 2019, some rights reserved.Creative Commons License EXTERNAL CONTROL OF ORTHO-PHENYLENE FOLDING by Gopi Nath Vemuri is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by Miami University and OhioLINK.