The Solid Phase Synthesis of M-Phenylene Ethynylene Oligomers and Its Application to the Synthesis of Covalent Molecular Ladders
Elliott, Erin L.
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https://hdl.handle.net/2142/84308
Description
Title
The Solid Phase Synthesis of M-Phenylene Ethynylene Oligomers and Its Application to the Synthesis of Covalent Molecular Ladders
Author(s)
Elliott, Erin L.
Issue Date
2008
Doctoral Committee Chair(s)
Moore, Jeffrey S.
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Organic
Language
eng
Abstract
With the advent of a practical solid phase synthesis of m-phenylene ethynylene oligomers their use as building blocks for the synthesis of 2D grids was attempted. In order to assess the practicality of forming large 2D grids through the use of dynamic covalent chemistry we first targeted the self-assembly of complimentary oligomers into [n]-rung ladders. We chose to employ imine formation as a chemical cross-link to capitalize on the self-correcting benefits of dynamic covalent chemistry to target the thermodynamically favored grid product. We found by mixing polyaldehyde and polyamine oligomers and utilizing Sc(OTf)3 as a Lewis acid catalyst we were able to form a series of molecular ladders from 3-6 rungs in length. 3 and 4-rung ladders were almost exclusively formed; however a large amount of high molecular weight by-product was formed in the 5 and 6-rung ladder reactions. A scrambling experiment was initiated was initiated which revealed that covalent molecular ladders become kinetically trapped at the 4-rung stage. This study helped reveal the design elements necessary for the successful construction of large 2D grids. A preorganization factor such as a covalent girder, H-bond or metal coordination will be necessary for the formation of large nanostructures from m-phenylene ethynylene oligomers. An appendix also describes efforts towards the use of heterosequences as a method to limit the number of possible by-products in ladder formation.
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