The highly preorganized ligand 2,9-BIS(Hydroxymethyl)-1,10-Phenanthroline, and its complexation properties with metal ions

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Raymond Thomas Gephart III (Creator)
The University of North Carolina Wilmington (UNCW )
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Robert Hancock

Abstract: Preorganization has been shown to be an important concept in inorganic chemistry. Preorganization increases the thermodynamic stability of complexes and metal ion selectivity of ligands. A ligand is more highly preorganized the more nearly it is constrained as the free ligand to be in the conformation required to complex the metal ion. The ligand 2,9-bis(hydroxymethyl)-1,10-phenanthroline (PDALC) was used to study the effects of preorganization and effects of addition of neutral oxygen donor atoms on the thermodynamic complex stability. The rigid extended aromatic backbone of PDALC should lead to unprecedented levels of preorganization for a non-macrocyclic ligand. PDALC was synthesized and characterized using NMR and IR analysis. UV/Vis spectrophotometry was used in titrations to determine protonation constants of the free ligand and its formation constants with metal ions. These were obtained by plotting absorbance, corrected for dilution caused by addition of acid or base during the titration, against pH. Log K1 values for PDALC were obtained for Ba(II), Bi(III), Ca(II), Cd(II), Co(II), Cu(II), Gd(III), In(III), La(III), Mg(II), Ni(II), Pb(II), Sr(II), Zn(II), and Zr(IV) in 0.1 M NaClO4 at 25 oC. A titration with Zr(IV) was used to determine the charge of the complex at biological pH for potential use in positron emission tomography (PET). The crystal structures of the PDALC complexes [Bi(PDALC)(H2O)2](ClO4)3·H2O, [Pb(PDALC)(ClO4)2]· H2O, and [Ca(PDALC)2](ClO4)2·H2O are reported. The stability constants along with crystal structures are discussed in relation to the high level of preorganization of the PDALC ligand, and the effects of the neutral O-donors of the hydroxymethyl groups of PDALC on its complexes.

Additional Information

A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment of the Requirement for the Degree of Masters of Science
Language: English
Date: 2009
Inorganic compounds--Synthesis, Ligands--Synthesis, Metal ions--Analysis
Ligands -- Synthesis
Metal ions -- Analysis
Inorganic compounds -- Synthesis

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