Photochemical Sciences Ph.D. Dissertations

Title

Metal-organic Frameworks as Modern Tools for Isomerism, Photophysics and Spin Chemistry

Date of Award

2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Photochemical Sciences

First Advisor

Malcolm D.E.Forbes (Advisor)

Second Advisor

Alexis Ostrowski (Committee Member)

Third Advisor

Pavel Anzenbacher (Committee Member)

Fourth Advisor

Ilyoung Ju (Other)

Abstract

We present studies that showcases metal-organic frameworks as suitable platforms that can mediate molecular interactions by its tunable structural architecture, to enhance the functionality of its incorporated molecules towards potential applications. Other projects include studies on inorganic complexes and other materials using electron paramagnetic resonance (EPR) as a chief tool to investigate these dynamic systems.

Our first project aimed at designing novel types of fluorescent multivariate MOF to produce white light emitting materials. We highlighted the ability to carry over solution state luminescent properties of select push-pull fluorophores based on 2,5-disubstituted diacrylic benzene, 2,5-disubstituted distyrylbenzene, and 2,5-disubstituted diethylnylbenzene into a MOF structure. The SBU concept was utilized to achieve suitable topologies that can mitigate florescence quenching. Some of these MOFs were also used to isolate singular rotamers of two rotermer often mixed in solution state photophysics, and this could be a means to study such isolated rotamers.

We were also able to design and construct a novel pillared MOF containing a 2D-array of well-ordered organic qubit candidate made from a diethynylpyridine isolidine nitroxides backbone as pillar linkers. Inter–qubit distances were tuned by mixing the pillar linkers with magnetic neutral linkers without nitroxides groups. Due to the anisotropic nature of these materials, steady-state electron paramagnetic resonance (SSEPR) technique was very useful to characterize properties of these materials. EPR variable temperature studies unveiled spin-spin interaction and its changes as the inter-qubit distances were tuned. Extent of spin-lattice and spin-spin interactions are important information needed when considering qubits for potential application in advancing quantum information science.

Spin probing and spin trapping techniques were used to investigate different types of system. We were able to use 5,5-dimethyl-1-pyrroline N-oxide (DMPO) spin traps to reveal mechanistic clues in hypothesizing reaction pathways of Fe (III) photo-reduction chemistry through the generation of transient CO2•− radical intermediates. Microenvironment dynamics of drying latex paints were also determined using TEMPO spin probes to observe the SAG effects of paint coated on a vertical surface versus the one on a horizontal surface. The creation of different microenvironment in the drying that experience SAG effect was observed. These studies can be beneficial for the industry as a quick method to carry out quality control on production line and also to develop best additives that could mitigate the SAG effect in paint. Also, EPR and absorption spectroscopy methods were able to reveal the catalytic properties of catechol oxidase biomimetic models constructed from an unconventional coordination pattern of a pentadentate linker to the copper centers.

Lastly, reversible Vanadium (V)/ (IV) photochemistry in vanadium tartrates was determined by EPR in combination with other spectroscopic techniques. This reaction proceeds to light initiation and reversed by oxidation from atmospheric oxygen. A mixed valence intermediate was identified and proposed reaction mechanism was hypothesized as the possible pathway for this reaction under the set conditions.

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