The kinetics of ligand exchange of seven-coordinate molybdenum(IV) and eight-coordinate europium(III) compounds

• Main Author: Hatwell, Karen Rachel
• Language: ENG
• Published: ScholarWorks@UMass Amherst 1999
• Subjects: Chemistry
• Online Access: https://scholarworks.umass.edu/dissertations/AAI9950158

This research involves three projects. The first area includes research on the kinetics of ligand exchange for three molybdenum(IV) compounds. The second area entails the kinetics and mechanisms of the dissociation of tetradentate Schiff-base compounds with europium(III). The third area shows attempts of the polymerization of Na[Eu(dshp)2]. The molybdenum(IV) compounds studied contained the ligands 5,7-dicholor-8-hydroxyquinolinol and the chloride ion. The compounds were reacted in methylene dichloride with either more 5,7-dicholoro-8-hydroxyquinolinol or picolinic acid. The kinetics of the ligand exchange reactions were followed using absorption data following changes in the spectra. Reaction rates and activation parameters were found for the three reactions studied. Studies of the reaction rate as a function of concentration show that the reactions are dissociative in nature. The second part of this research involved the dissociation of europium(III) and yttrium(III) coordination compounds with salen and its derivatives in dimethyl sulfoxide. This reaction is followed by monitoring the decrease of europium(III) compound emission peaks and the growth of ligand emission as well as by absorption spectral changes. The reaction rates, activation energy, and reaction mechanism information were obtained for this exchange using the emission and absorption data. Several conclusions were made for this study of solvent insertion into the compound. Firstly, this reaction is not affected by light. Secondly, the solvent can affect the kinetics in that dimethyl formamide and dimethyl sulfoxide are rate increasing solvents compared to water. Thirdly, the 2 to 3 compounds have generally a faster rate than the 1 to 2 compounds and the reactions. And fourthly, the compounds with a six-member chelating ring and an electron-withdrawing hydroxyl group are more kinetically stable than those with five member chelating rings. The final part of this research involved the polymerization of Na[Ln(dshp)2], where Ln = Y, Eu, with isophthalolyl chloride and terephthalolyl chloride. The resulting compounds were then analyzed and emission data measured for the europium species. However, the results did not support the formation of polymers.