The highly preorganized ligands 8-(2-Pyridyl) Quinoline, 2,2'-dipyridyl amine and 1,10-phenanthroline-2, 9-dicarboxylic acid, and their complexing properties with metal ions

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

Abstract: Highly preorganized ligands are those that are constrained as the free ligands to be in the conformation required to complex the target metal ion. Such ligands have been shown to form more stable complexes, and display higher metal ion selectivity than less preorganized analogs. These ligands have become of particular interest in a variety of different areas, including biomedical, environmental, nuclear and industrial applications. The preorganized ligands 8-(2-pyridyl)Quinoline (8PQ), 2,2’-dipyridyl amine (DIPY), and 1,10-phenanthroline-2, 9-dicarboxylic acid (PDA) and their complexing properties with metal ions are explored in this project. The interest in 8PQ and DIPY is that they form six-membered chelate rings on complex-formation. Following rules on ligand design1 , ligands that form six-membered chelate rings should show selectivity for smaller metal ions as compared to analogs such as 2,2’-bipyridyl that form five-membered chelate rings.Thus, 8PQ and DIPY can be compared in this regard to BIPY, which forms a fivemembered chelate ring. Titration experiments were carried out on aqueous solutions of these ligands and metal ions in order to determine their formation constants. UV-Vis spectrophotometry was used to monitor the equilibria involved in the formation of metalligand complexes. The log K1 values for the formation of metal-ligand complexes were determined from UV absorbance data as a function of pH, and are reported in 0.1 M NaClO4 at 25.0ºC. Formation constants (log K1, in parentheses) for 8PQ with Cd(II) (2.19), Ca(II) (0), Cu(I) (4.66), Cu(II) (4.37), Ni(II) (3.3), and Zn(II) (3.48); DIPY with Al(III) (0), Cd(II) (2.67), Co(II) (4.36), Cu(II) (7.34), Ga(III) (0), Ni(II) (6.15), and Zn(II) (3.52); and PDA with In(III) (19.78) and UO2 2+ (19.78) are reported. The results are discussed in terms of the role of chelate ring geometry in controlling metal ion selectivity.

Additional Information

A Thesis Submitted to the University of North Carolina Wilmington in Partial Fulfillment of the Requirements for the Degree of Master of Science
Language: English
Date: 2009
Chemistry Organic, Ligands (Biochemistry), Ligands--Synthesis
Chemistry, Organic
Ligands (Biochemistry)
Ligands -- Synthesis