Selective Sensing of Ions and Ion Pairs of Environmental and Forensic Significance

Authors

Tosin Mobolaji Jonah, Florida International UniversityFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Chemistry

First Advisor's Name

Konstantinos Kavallieratos

First Advisor's Committee Title

Major advisor

Second Advisor's Name

José R. Almirall

Second Advisor's Committee Title

committee member

Third Advisor's Name

Bruce R. McCord

Third Advisor's Committee Title

committee member

Fourth Advisor's Name

Francisco A. Fernandez-Lima

Fourth Advisor's Committee Title

committee member

Fifth Advisor's Name

Chenzhong Li

Fifth Advisor's Committee Title

committee member

Keywords

ions, Ion-pairing, pyrazole, ammonium ion, dual- host receptor, dual host

Date of Defense

11-17-2017

Abstract

Dual-host combinations of cation and anion sensors have unique potential for selective detection of ion pairs, such as NH₄NO₃, via solvent extraction. Selective sensors for NH₄⁺ and NO₃^- were synthesized and used together for ion-pair sensing of ammonium nitrate both in organic solvents (using Bu₄N⁺NO₃ ^- and NH₄⁺PF₆^-) and in extraction of NH₄NO₃ from water into dichloromethane. A fluorescent sensor for NH₄⁺ based on 1,3,5-triethylbenzene shows remarkable binding and sensing selectivity for NH₄⁺ vs. K⁺. Fluorescence and ¹H-NMR titrations reveal surprising differences in sensing properties and binding constants for the tris-(3,5-dimethyl)pyrazole vs. the tris(3,5-diphenyl)pyrazole. The role of ion pairing and solvation is revealed by X-ray and theoretical DFT studies. We have also demonstrated a unique dual-host extraction-based ion-pair sensing paradigm using Förster Resonance Energy Transfer (FRET), showing selectivity for NH₄NO₃. The fluorescence emission of the NH₄⁺ sensor tris-(3,5-dimethyl)pyrazole (305-340 nm), is compatible with the excitation wavelength of the dansyl fluorophore of the nitrate sensor 1,3,5-Tris-(5-dimethylamino-1-naphthalenesulfonamido)methyl]-2,4,6-triethylbenzene, thus resulting in FRET emission upon combined use of these two sensors for the NH₄NO₃ ion pair. Contact of dichloromethane solutions containing the two hosts with aqueous solutions of NH₄NO₃ (1 x 10^-5 M to 1 x 10^-4 M ), resulted in FRET fluorescence enhancements at 510 nm, with increasing concentrations of NH₄NO₃, while NaNO₃, KNO₃, NaCl and KCl showed only minimal fluorescence responses, under identical conditions. The ability of the tris-pyrazole to bind cations, such as NH₄⁺, was also exploited in a detailed fluorescence and ¹H-NMR Ln(III), binding study using tris-pyrazoles with varying substitution patterns. The dependence of fluorescence responses on pyrazole substitution that had been observed for NH₄⁺ was also observed for different Ln(III), indicating the significant role of ion pairing for Ln(III) binding and fluorescence sensing. Likewise, the tris-dansyl nitrate receptor, in its deprotonated form, was also found to be an efficient Hg(II) fluorescent sensor. An X-ray crystal structure showed the ability of the trianionic version of this receptor to bind three Hg(II) atoms, also containing three CH₃COO^- counteranions. The X-ray crystal structure of the same receptor with HgCl₂ gave a 2:1 complexation pattern, with one Hg atom complexed by two bis-deprotonated receptor molecules

Identifier

FIDC004059

Recommended Citation

Jonah, Tosin Mobolaji, "Selective Sensing of Ions and Ion Pairs of Environmental and Forensic Significance" (2017). FIU Electronic Theses and Dissertations. 3498.
https://digitalcommons.fiu.edu/etd/3498