Date of Award

3-10-2019

Publication Type

Doctoral Thesis

Degree Name

Ph.D.

Department

Chemistry and Biochemistry

Keywords

Metal-Organic Frameworks, Molecular Switches, Poprhyrin, Rotational Dynamics, Rotaxane, Supramolecular Chemistry

Supervisor

Stephen Loeb

Rights

info:eu-repo/semantics/openAccess

Abstract

The work herein describes the synthesis and characterization of rotaxane molecules, the incorporation of a selection of these molecules into metal-organic frameworks (MOFs), and the study of how these rotaxanes respond to external stimuli such as changes in temperature and chemical environment, both in solution and when immobilized inside a MOF. Chapter 1 introduces the concepts utilized during this work and presents a general overview of the state of the field. Chapter 2 describes the fabrication of the first porphyrin-based MOFs incorporating a rotaxane linker, UWDM-7 and -8. Their structures were analyzed by single-crystal X-ray diffraction (SC-XRD), powder X-ray diffraction (PXRD), and the rotational dynamics of the crown ether rings were studied with variable temperature (VT) 2H solid-state nuclear magnetic resonance spectroscopy (SSNMR). It was found that the rotation of these rings could be controlled by modifying the rigidity of the framework and by adding/removing guest solvent molecules within the pores of the materials. Chapter 3 presents an initial approach to the use of reticular chemistry applied to MOFs containing mechanically interlocked molecules and porphyrins. The synthesis of two porphyrin linkers is described. Another example of a mixed-linker MOF, UWDM-9, is presented and its structural features are described. The topological analysis of UWDM-9 resulted in the report of the first occurrence of the tui topology. Preliminary VT 2H SSNMR studies are presented, and they a show lower activation energy for the partial rotation of the crown ether macrocycles compared to other UWDM MOFs. Chapter 4 describes a new method for the synthesis of rotaxanes with high compositional complexity. [5]Rotaxanes were synthesized using a capping method in a one-pot reaction that also creates a porphyrin core. This new synthetic route allows for the incorporation of various substituent groups on these molecules, different crown ether molecules, as well as recognition sites. Six [5]rotaxanes are presented and characterized using XRD, NMR spectroscopy, and mass spectrometry. In Chapter 5, some of these [5]rotaxanes are tested as linkers in the synthesis of MOFs. The process to decide the conditions to test and which structures to target is described, along with simulations supporting some of the findings. Finally, Chapter 6 puts the findings of this work in retrospect and analyzes potential future work derived from this dissertation and contemplates the directions the broader field might take.

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