Portland State University. Department of Chemistry
Date of Award
Doctor of Philosophy (Ph.D.) in Chemistry
1 online resource (xxii, 157 pages)
This work describes several thiophene-based molecular sensors and various modifications aimed to improve and understand the photophysical and supramolecular properties, such as the association constant (Ka) and selectivity, towards the development of a selective mercury(II) sensor. From the first generation of sensors containing pyridine and thiophene groups, it was determined that thiophene can offer good selectivity for mercury(II) against other transition metal ions, and provide a ratiometric absorption and fluorescent response. The projects following this focused on improving the Ka of the first generation of sensors through several different strategies. Substitution of thiophene for dibenzothiophene was shown to improve the Ka however this resulted in less than ideal photophysics of the dibenzothiophene sensors with absorption and emission in the UV-region. In addition to the effect of the chelating group was examined by incorporating imidazole, and thiazole rings, to compare to the original pyridyl chelating group employed. From this it was determined that pyridine offered the greatest Ka and selectivity for mercury(II). Following this electron-donating groups, including alcohol, octaethyleneglycol monomethyl ether, and amine, were added to a sensor, 2,5-bis(2-pyridyl)thiophene, as an alternative strategy to improving the Ka. Initially these functional groups were placed on the pyridine ring which caused a great increase in affinity for transition metal ions such as iron(II) and copper(II), however this translated to a loss in selectivity. In the final project I functionalized the thiophene ring with the same electron-donating groups which resulted in an increased Ka and maintained good selectivity for the mercury(II) ion, though iron(III) was still a competitive binder. In addition to this one of these thiophene functionalized sensors, 2,5-di(pyridin-2-yl)thiophene-3,4-diol, was shown to have a specific response to copper(II), iron(III), lead(II) and mercury(II) suggesting it could be used as a model for the development of a small-molecule multiplex sensor. Herein I will describe this work in greater detail and focus on the effects the modifications discussed had on the Ka and selectivity for the mercury(II) ion.
Shigemoto, Austin Kazuo, "Thiophene-Based Molecular Sensors towards the Selective Detection of Mercury(II) and Other Metals" (2018). Dissertations and Theses. Paper 4517.
Available for download on Tuesday, August 06, 2019