OUTER COORDINATION SPHERE - CHARACTERIZATION BY NUCLEAR MAGNETIC-RELAXATION DISPERSION

Nuclear magnetic relaxation dispersion data obtained on aqueous solutions of potassium tris(oxalato)chromate(III), potassium tris(malonato)chromate(III), and potassium hexacyanochromate(III) provide a characterization of magnetic relaxation effects in the outer coordination domains of the metal complexes. The data demonstrate that the water proton nuclear spin relaxation is not controlled by rotational motions of the metal complex but by the relative translational motions of the water molecules and the metal complex and, in some cases, by the electron relaxation in the metal center. Unlike previous analyses using similar approaches that employed less complete interpretive models, the present data demonstrate that the translational mobility of the water in the regions immediately adjacent to the metal ion are perturbed very little compared with properties of bulk water. © 1990 American Chemical Society.