Date of Award

5-2026

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

School

Mathematics and Natural Sciences

Committee Chair

Dr. Wujian Miao

Committee Chair School

Mathematics and Natural Sciences

Committee Member 2

Dr. Karl J Wallace

Committee Member 2 School

Mathematics and Natural Sciences

Committee Member 3

Dr. Julie Pigza

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. Douglas Masterson

Committee Member 5 School

Mathematics and Natural Sciences

Abstract

Organic luminophores with tunable photophysical and electrochemical properties are important for chemical sensing and light-emitting applications. Coumarin-based systems are promising candidates for the development of functional luminophores.

In Chapter II, fused coumarin-quinoline derivatives (2.27-2.31) and 4-aminocoumarin-3-formyl derivatives (2.32-2.36) were synthesized under acid-promoted conditions, where reaction time and temperature controlled the formation of fused and non-fused products. All compounds were characterized by 1D (1H, 13C, and 13C APT) and 2D (HSQC, HMBC, COSY) NMR spectroscopy, FTIR spectroscopy, and high-resolution mass spectrometry, and selected compounds were further confirmed by X-ray crystallography. The fused derivatives showed dual absorption bands, with compound 2.28para displaying absorption at 375 and 425 nm in toluene and emission at 530 nm, with Stokes shifts of 155 and 105 nm, respectively. In contrast, the non-fused derivatives showed a single absorption band and weak emission. These results indicate that quinoline annulation and increased conjugation promote efficient fluorescence in this scaffold.

In Chapter III, coumarin-quinoline ketoxime 3.1 and ketomethoxime 3.2 were synthesized in good yields (85-87%). The compounds were investigated for aggregation-induced fluorescence and electrogenerated chemiluminescence behavior. In MeCN, both compounds exhibited intramolecular charge-transfer emission at 615 nm with a Stokes shift of 190 nm. In MeCN-H2O mixtures, compound 3.1 showed aggregation-dependent fluorescence, with a decrease in emission intensity up to approximately 65% fw followed by a sharp increase beyond 70% fw, reaching a maximum 5.6-fold enhancement at 90% fw. This change was accompanied by a blue shift in emission from 615 to 560 nm. Electrochemical studies showed that compound 3.1 functions as an efficient electrogenerated chemiluminescence luminophore using tri-n-propylamine as the anodic coreactant, with an approximately 10-fold enhancement at 70% fw, demonstrating aggregation-enhanced electrogenerated chemiluminescence behavior.

In Chapter IV, coumarin-enamine chemodosimeters 4.43a and 4.43b were synthesized for the electrogenerated chemiluminescence detection of diisopropyl fluorophosphate (DFP), a sarin mimic. Electrochemical studies using cyclic voltammetry and differential pulse voltammetry assigned multiple oxidation processes associated with the functional groups within the molecular framework. In the presence of [Ru(bpy)3]2+, probe 4.43a showed a progressive increase in electrogenerated chemiluminescence intensity upon addition of DFP, whereas probe 4.43b showed no significant response. These results confirm the role of the oxime functionality in the sensing mechanism and demonstrate the system's applicability for DFP detection.

ORCID ID

0000-0001-7714-3593

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Available for download on Thursday, May 01, 2036

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