Date of Award

8-16-2024

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

First Advisor

Ken Shimizu

Abstract

This thesis describes the development of molecular machines as analytical instruments to measure the strength of non-covalent interactions and to test hypotheses of reaction mechanisms. The first chapter is a review of molecular rotors. The second chapter presents the development of a molecular rotor that can be controlled using electrostatic interactions. Previous examples have used electrostatic interactions to slow down or inhibit molecular motion. Our system is activated and sped up using electrostatic interactions. The third and fourth chapters describe the application of molecular rotors designed to experimentally measure the strength and stability trends for non-covalent pnictogen and chalcogen interactions. Chalcogen bonds involve group VI (oxygen, sulfur) atoms, and pnictogen bonds involve group V (nitrogen). The fifth chapter presents molecular rotors designed to model reaction transition states to test mechanistic hypotheses. For example, the interactions between electron-rich and electron-deficient groups in our rotors were used to test the hypothesis that secondary electrostatic interactions can explain the enhanced reactivity of benzyl and allyl electrophiles in SN2 reactions.

Techniques used in the described research include organic synthesis, dynamic NMR methods, and DFT calculations. The molecular machines were primarily synthesized via condensation and metal-catalyzed coupling reactions. Dynamic NMR methods, including 2D EXSY and 1D lineshape analysis, were used to measure the rotational barriers. DFT calculations were performed on multiple platforms like Spartan and Q-Chem to reproduce the molecular barriers and analyze the origins of the interactions.

Rights

© 2024, Binzhou Lin

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