New insight into the coordination and reactivity of hetero-substituted maltol and method development for complex mixture analysis of asphaltene.

Spiegel, Michael T., 1992-

New insight into the coordination and reactivity of hetero-substituted maltol and method development for complex mixture analysis of asphaltene.

dc.contributor.advisor	Farmer, Patrick Joseph, 1957-
dc.creator	Spiegel, Michael T., 1992-
dc.date.accessioned	2020-09-04T18:25:26Z
dc.date.available	2020-09-04T18:25:26Z
dc.date.created	2019-12
dc.date.issued	2019-09-05
dc.date.submitted	December 2019
dc.date.updated	2020-09-04T18:25:26Z
dc.description.abstract	The metal complexes of maltol and its hetero-substitutions have a wide variety of bioinorganic applications. However, the latest addition to this family of molecules, 3-hydroxy-2-methyl-4H-pyran-4-selenone (selenomaltol), had not previously had its metal complexes characterized. To remedy this, transition metal complexes were made using Fe(III), Ni(II), Cu(II) and Zn(II) to characterize the homoleptic-complexes of selenomaltol and compare them to previously published maltol-like ligands. The selenomaltol complexes were found to be similar to thiomaltol complexes. In addition, new insights were gained into the redox chemistry of the thiomaltol and selenomaltol ligands, and the complexes of selenomaltol and thiomaltol were found to be more aromatic than the free ligand. The increased aromaticity of the complexes over the ligands was thought to be due to the complexes stabilizing the pyrylium resonance structure of hetero-substituted maltols. To explore if the free ligand exhibited this resonance, NMR spectroscopy and reactivity studies were performed. Polar solvents seemed to favor the pyrylium resonance, and significantly impacted the nucleophilicity of the hetero-substituted maltol ligands. This reactivity study led to the generation of the two new ligands 3-hydroxy-2-methyl-4-(methylsulfanyl)pyrylium and 3-hydroxy-2-methyl-4-(methylselanyl)pyrylium. This new ligand class is of interest as it contains a stable pyrylium species, which can be used to generate a new family of ligands for use in bioinorganic chemistry. The second project explored was on the development of a new method for investigating asphaltenes, the heaviest and most problematic fraction of crude oil, by NMR spectroscopy and mass spectrometry. To study asphaltenes by mass spectrometry, we reacted a sample of asphaltene with elemental bromine (Br2). This was done to selectively substitute the aromatic protons on asphaltenes to probe their structure. The subsequent high-resolution mass spectra were visualized by Kendrick Mass Defect (KMD) plots. These reactivity studies showed fewer aromatic protons available to react than predicted by current models of asphaltene. To more accurately characterize the number of aromatic protons present, a new method for performing 1H NMR spectroscopy was developed, which removed paramagnetic materials from the sample.
dc.format.mimetype	application/pdf
dc.identifier.uri	https://hdl.handle.net/2104/10992
dc.language.iso	en
dc.rights.accessrights	Worldwide access.
dc.rights.accessrights	Access changed 5/23/22.
dc.subject	Selenomaltol. Maltol. NICS. Crude oil. KMD. NMR. Asphaltene.
dc.title	New insight into the coordination and reactivity of hetero-substituted maltol and method development for complex mixture analysis of asphaltene.
dc.type	Thesis
dc.type.material	text
local.embargo.lift	2021-12-01
local.embargo.terms	2021-12-01
thesis.degree.department	Baylor University. Dept. of Chemistry & Biochemistry.
thesis.degree.grantor	Baylor University
thesis.degree.level	Doctoral
thesis.degree.name	Ph.D.