Date of Award

Summer 8-2016

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry and Biochemistry

School

Mathematics and Natural Sciences

Committee Chair

Karl J. Wallace

Committee Chair Department

Chemistry and Biochemistry

Committee Member 2

Douglas Masterson

Committee Member 2 Department

Chemistry and Biochemistry

Committee Member 3

Vijay Rangachari

Committee Member 3 Department

Chemistry and Biochemistry

Committee Member 4

Wujian Miao

Committee Member 4 Department

Chemistry and Biochemistry

Committee Member 5

Song Guo

Committee Member 5 Department

Chemistry and Biochemistry

Abstract

Many anions and metal ions are of biological and environmental importance. This work describes our attempts to synthesize molecular probes to specifically target cyanide, zinc, cadmium and mercury as these species can often result in negative effects to the environment and the human body.

The work in this dissertation, describes the synthesis of a family of coumarin-enamine chemodosimeters, in a straightforward synthetic procedure, the reaction between 7-(diethylamino)-4-hydroxycoumarin and a primary amine. The work presented in this dissertation demonstrates that these molecules can play dual roles and therefore the work is split into two distinct parts: Part 1 describes one role of theses molecular probes. In this first section three members of the coumarin-enamine family showed selectivity towards the cyanide ion over other anions studied (F-, Cl-, Br-, I-, NO3-, OAc-, H2PO4-, HSO4-, BF4-, N3-, SCN-, ClO4-, and OH-) in DMSO, with a detection limit as low as 4.2 ppb. The kinetics of the Michael addition was also investigated with a fluorescent response time calculated to be approximately (t1/2 = 20 s).

The second role of these molecular probes was to investigate and decimate structurally similar metal salts (Na+, Mg2+, Ca2+, Cr3+, Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Pd2+, Ag+, Cd2+, Hg2+, and Pb2+), in particular the chloride and acetate salts. A univariate approach was used. The participation of the acetate anion is key for the probe to selectively bind the metal via the enaminone chelating motif. These molecular probes showed preference to zinc acetate salt whereby the chromophore utilized a duel signaling mechanism, inhibition of ESIPT which either quenches the fluorescence signal or shifts the band in the blue direction. Then upon the addition of the zinc(II) ion a CHEF mechanism increases the fluorescence signal upon the coordination of the metal ion. The limit of detection was calculated to be 7.4 ppb.

This work extensively used various analytical methods to detect and monitor these analytes in particular UV-Vis and fluorescence spectroscopy. Additional techniques, for example NMR, IR, ESI-MS, and X-Ray were all utilized to help our understanding of the coordination environment of the molecular probe and the metal ions.

ORCID ID

0000-0002-4099-931X

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