Date of Award

10-5-2017

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Chemistry and Biochemistry

First Advisor

Loeb, Stephen

Keywords

Mechanically Interlocked Molecules, Metal-Organic-Materials, Rotaxane, Supramolecular Chemistry

Abstract

This dissertation focuses on studies of mechanically interlocked molecules (MIMs) specifically [2]rotaxanes in three principle areas: (1) creating [2]rotaxane linkers to incorporate into metal-organic frameworks (MOFs); (2) studying the rate of shuttling motion in solution and finally (3) investigating the shuttling motion inside the MOF. Chapter 1 provides a brief introduction to MIMs, rotaxanes, MOFs and all previous studies on dynamic motions of MIMs in MOFs. Chapter 2 describes a [2]rotaxane linker with donor atoms attached to both the axle and the wheel. The linker contains four carboxylate groups attached to a rigid, H-shaped axle and two carboxylate units appended to a crown ether wheel. In the resulting Zn-based MOF, three independent 3-periodic frameworks (threefold interpenetration) are interconnected only by virtue of the threading of their individual components in the rotaxane linker. In Chapter 3, a [2]rotaxane linker was synthesized which combines an H-shaped axle containing four 3-carboxyphenyl groups and a macrocyclic wheel with two 4-pyridyl groups. The synthesized Zn and Cu MOFs showed two independent lattices threaded together by interlocking of the linker. In Chapter 4, a series of [2]rotaxane molecular shuttles was synthesized with varying track lengths between recognition sites. The rates of shuttling of the macrocycle along the rigid track were measured by variable temperature 1H NMR spectroscopy for the neutral compounds and EXSY experiments for the dicationic species. It was determined that the length of the axle does not affect the shuttling rate. In Chapter 5, molecular shuttling inside Zr-based MOFs under acid-base conditions was studied. 13C SSNMR studies on the first MOF, UWDM-6 (University of Windsor Dynamic Material) consisting of two linkers 2′,3′,5′,6′-tetramethylterphenyl-4,4″ dicarboxylic acid (H4TTTP) and [2]rotaxane demonstrated no shuttling because of steric hindrance of methyl groups of H4TTTP linker. This steric hindrance limitation was eliminated for UWDM-7 by changing the linear ligand to terphenyl dicarboxylate (TPDC). In Chapter 6, a bistable [2]rotaxane molecular shuttle inside a Zr-based MOFs was studied. The synthesized MOF, UWDM-8 consisted of [2]rotaxane with two non-equivalent recognition sites and linear linker H4TTTP. Switching was driven by the addition of acid or lithium ions and monitored by 15N SSNMR spectroscopy.

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