Complexation of metal ions in aqueous solution by fluorescent ligands containing pyridyl groups

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Karen Anna Martha Oscarson (Creator)
The University of North Carolina Wilmington (UNCW )
Web Site:
Robert Hancock

Abstract: This research focused primarily on the induction of fluorescence by secondary ligands in solution. The Zn2+ ion, when complexed to fluorophoric ligands, is known to enhance the intensity of emission. With this in mind, both a fluorescence-quenching metal ion and a metal ion isoelectronic to Zn2+ (Ni2+ and In3+, respectively) were utilized in this research. The high-spin Ni(II) / terpyridine (terpy) complex was studied extensively due to the tendency of the d8 Ni2+ ion to quench fluorescence. Induction of fluorescence was attempted by addition of secondary ligands, primarily CN-. Ligands were chosen that are high enough in the spectrochemical series such as to increase the energy gap by raising the energy of the eg degenerate orbitals, giving rise to a low spin complex that could fluoresce. Although the induction of fluorescence was not achieved, the pK1 and pK2 of the Ni(II) / terpy hydrated complex was found by differential pulse voltammetry. X-ray crystallography further elucidated the Ni(II)/terpy /CN complex, revealing the two predominant species present, Ni(terpy)2 and [Ni(CN)4 ]2-. The In(III) / 1,10-phenanthroline (phen) complex was analyzed, and was found to fluoresce. NMR and differential pulse voltammetry were utilized for further characterization of In(III) / phen behavior in aqueous solution. LogK1 for the In(III) / phen complex was found by plotting nbar versus pH from the NMR data, and was also found by a Nernstian slope obtained from differential pulse voltammetry. The two binding constants obtained from the two different methodologies differed by 0.2 logarithmic units, and were comparable to the literature value.

Additional Information

A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment Of the Requirements for the Degree of Master of Science
Language: English
Date: 2009
Fluorescence spectroscopy, Ligands--Synthesis, Metal complexes, Metal ions--Analysis, Metals--Analysis
Fluorescence spectroscopy
Metal ions -- Analysis
Ligands -- Synthesis
Metals -- Analysis
Metal complexes

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