Fast diffusion of the Cl- ion in the headgroup region of an oppositely charged micelle.: A 35Cl NMR spin relaxation study

Field-dependent Cl-35 spin relaxation rates have been measured in the micellar solution of C(16)TACl-D2O. The data are analyzed in terms of a fast hydration dynamics of the ion and a slower motion that consists of ion diffusion and micellar tumbling. This model provides a distinct motional correlation time of the Cl- ion from which it is concluded that, on the nanosecond time scale, the Cl- ion diffuses on the micellar surface close to its bulk diffusion speed. The hydration dynamics on the picosecond time scale differs from that in a dilute solution. These features are similar to that observed for Br- ions in the vicinity of aqueous micelles of C(16)TABr (Hedin, N.; Furo, I. J. Phys. Chem. B 1999, 103, 9640).