Date of Award

Fall 12-2021

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

School

Mathematics and Natural Sciences

Committee Chair

Dr. Karl J Wallace

Committee Chair School

Mathematics and Natural Sciences

Committee Member 2

Dr. Julie Pigza

Committee Member 2 School

Mathematics and Natural Sciences

Committee Member 3

Dr. Wujian Miao

Committee Member 3 School

Mathematics and Natural Sciences

Committee Member 4

Dr. Song Guo

Committee Member 4 School

Mathematics and Natural Sciences

Committee Member 5

Dr. Alamgir Hossain

Abstract

Two different types of molecular probes have been synthesized. The first family of probes is the coumarin class of compounds. These chemodosimters are referred to as Low Molecular Weight Fluorescent probes (LMFP). The other type of molecular probe is a macrocycle known as a pillar[5]arene receptor.

The chemodosimters (2.12a-c and 3.12a) were synthesized in four to five steps. The photophysical properties were extensively studied in various solvent systems (DMSO, CH3CN, DMF, MeOH, EtOH, Me2CO, MeCO2Et, CHCl3, C6H5Me, and C6H6). Dimethyl sulfoxide (DMSO) was found to be the most suitable solvent for the studies due to the high quantum yields (35 to 84%) and large Stokes Shift (126 nm), and the greatest solubility. A P4-t-Bu, a non-nucleophilic base, readily deprotonates the oxime functional group incorporated onto the organic scaffold, forming the oximate, which can readily undergo a phosphorylation reaction. Significant UV-vis and fluorescence changes were observed upon phosphorylation of organophosphates (DFP, DICP, omethoate, dimethoate, chlorfenvinphos) (in the range of 50 to 60 nm).

Interestingly, one of the molecular probes, 3.12a could simultaneously phosphorylate the OP and capture the CN- leaving group (DEPC-a Tabun Mimic) on the same receptor (a ditopic molecular host). Lifetime decay experiments help us understand the number of tautomers that could exist in the excited state. Each species lifetime decay profile is unique, aiding our understanding of the selectivity between the probe and analyte. The molecular probes were able to monitor the analyte with a Limit of detection in the ppb range.

The chemical structure of the molecular probes and their interactions with OPs were extensively studied using 1D and 2D NMR spectroscopy, X-ray crystallography, mass spectroscopy, and computer modeling calculation confirmed the experimental data. Moreover, initial electrochemical studies have shown that these probes can also be used as electrochemical sensors for OP detection.

The bowl-shaped macrocyclic pillar[5]arene (5.9) has been synthesized in four steps. The macrocycle was found to undergo conformational changes, leading to the formation of four isomers (cone, partially cone, and two alternate isomers). The crystal structure of 5.9-cone was obtained and is reported. 1D and 2D NMR studies were carried out to confirm the structure and initial host-guest studies show that the bowl-shaped molecule is showing promising behavior to form a host-guest complex with adamantane derived molecules.

ORCID ID

0000-0003-3209-4403

Available for download on Saturday, September 30, 2023

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