Solvent-Dependent Redox Thermodynamics of Metal Amine Complexes. The Delineation of Specific Solvation Effects
PURDUE UNIV LAFAYETTE IN DEPT OF CHEMISTRY
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Solvent-dependent formal potentials, Ef, and reaction entropies, for four reversible CoIIIII couples featuring macrobicyclic cage ligands have been obtained. These are utilized, together with corresponding data for other CoIIIII and RuIIIII amine couples and for MIIIII polypyridine couples, to unravel effects on the redox thermodynamics arising from specific ligand-solvent and other interactions. The solvent dependencies of Ef vs. ferrocenium-ferrocene for each redox couple are fitted by using a multiparameter approach, incorporating various well-known empirical quantities describing solvent basicity, acidity, polarity, and internal ordering. For most amine couples, solvent basicity appears to play a prevailing role, associated with interactions involving the amine hydrogens, although solvent polarity also exerts a substantial, albeit less solvent-dependent, influence upon EfD.
- Physical Chemistry