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Date of Award
Matthew J. Allen
LNII-CONTAINING CRYPTATES: SYNTHESIS AND PROPERTIES
AKHILA N. W. KUDA-WEDAGEDARA
Advisor: Dr. Matthew J. Allen
Degree: Doctor of Philosophy
Research projects described in this dissertation are focused on studying the physicochemical properties, including the photochemical, redox, and magnetic properties, of LnII-containing cryptates and how ligand structure influences metal–ligand interactions that in turn influence physicochemical properties. The results of these studies enable tailoring of the coordination properties of metal complexes that are important in applications including luminescent materials, chemical reductions, catalysis, and imaging.
A EuII-containing cryptate 2.1-EuII synthesized with an amine-rich ligand displayed bright yellow luminescence in aqueous solution with a quantum yield of 26% that is so far the highest quantum yield reported for EuII in aqueous solution. The bright luminescence of the complex 2.1 was likely a result of the absence of coordinated water molecules based on solid- and solution-phase characterization. Additionally, the X-ray crystal structure revealed a rare 9-coordination staggered hula-hoop geometry.
Investigation of coordination chemistry of the EuII ion with ether-rich and amine-rich cryptates synthesized with ligands 1.7, 1.17, 3.1, and 2.1 revealed that field strength of ligands influence the physicochemical properties where strong-field ligands shift the absorption and emission spectra toward lower energy and the oxidation potentials to more negative potentials relative to weak-field ligands. X-ray crystal structures of 3.1-EuII and 2.1-EuII displayed eclipsed and staggered hula-hoop geometries.
The use of the ligand series 1.7, 1.17, 3.1, and 2.1 with the YbII ion displayed similar shifts in absorption spectra and oxidation peak potentials. X-ray crystal structures of 3.1-YbII and 2.1-YbII revealed 9-coordinate eclipsed hula-hoop and 8-coordinate bicapped trigonal antiprism geometries, respectively.
Investigation of influence of coordination environment of structurally varied cryptand-type
ligands on the physicochemical properties of LnII ions revealed that ligand-field strength, the strength of the metal-ligand interactions, and the size match between metal ions and cryptand cavities are important parameters in selecting ligands for these metal ions. Furthermore, optimization of these parameters could result in increased metal-ligand orbital interactions leading to dramatic changes in physicochemical properties of LnII-containing cryptates that are potentially useful in luminescence, redox, and synthetic applications.
Kuda-Wedagedara, Akhila Nuwan Wijerathne, "Ln(ii)-Containing Cryptates: Synthesis And Properties" (2015). Wayne State University Dissertations. 1719.