Limiting interdiffusion coefficients of Tris(acetylacetonato)cobalt(III) in water and in organic solvents

The diffusion coefficients of tris(acetylacetonato)-cobalt(III) in water (5, 15, 25, and 40°C), methanol (25°C), ethanol (15, 25, and 45°C), 1-propanol (25°C), 1-butanol (45°C), acetone (25 and 40°C), 2-butanone (25°C), acetonitrile (25°C), tetrahydrofuran (25°C), benzen (25°C), toluene (25°C), and carbon tetrachloride (25°C) have been measured at concentrations close to infinite dilution. The Stokes-Einstein coefficient (f=kT/Dr) has been calculated for Co(acac)₃ in each solvent and is found to be larger in water than in organic solvents. Furthermore, it increases as the temperature is lowered (or as the viscosity is increased) in water while it decreases with increasing viscosity of organic solvents. The differences are discussed in terms of the enhancement of the water structure by the solute.