| Abstract
| - In aqueous solution, the stability, the structure, and the lability of 12 vanadium(V) complexes weredetermined and related to the amino alcohol ligand properties. The amino alcohols were chosen to maintaina five-coordinate vanadium geometry in the vanadium complex and were based on diethanolamine as theparent ligand. Apparent and composite stability constants were determined for all 12 complexes. Selectedcomplexes were further examined to determine solution structure, lability, and thermodynamic properties. Weempirically show that the formation constants for the series of 12 complexes, when plotted as a function of thepKa value for the protonated amino alcohol, generate a curve that initially increases as the pKa value increasesand then decreases as the pKa value continues to increase. The observed associations suggest that the electron-donating capacity of the amino alcohol plays a major role in complex stability; however, metal coordinationnumber, sterics in the amino alcohol, and solvation also are found to affect the stability. Determination of thethermodynamic parameters of selected complexes showed that the enthalpic component was the major contributorto the stability of the complex, but that the entropic component opposed this term. A series of studies wasconducted to examine whether the lability of these complexes varied from the parent complexes. Unfortunately,the variation in the lability of these complexes was much less than the variation in complex stability. Insummary, these studies describe quantitatively the variation in complex stability and lability as the structureof amino alcohol is modified and explain why some complexes show less stability than predicted on the basisof the pKa value. In short, this study provides valuable information for the design of additional vanadiumcomplexes with specific properties.
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