3980
J. Am. Chem. SOC.1994, 116, 3980-3987
Multinuclear Magnetic Resonance Study of Saponite Hydration and of Acetonitrile-Water Competition Jean Grandjean and Pierre Laszlo' Contribution from the Laboratoires de chimie fine aux interfaces, Universiti de Libge au Sart- Tilman, 4000 Li.?ge, Belgium, and Ecole Polytechnique, 91 I28 Palaiseau, France Received July 7, 1993. Revised Manuscript Received January 24, 1994"
Abstract: Saponite is a trioctahedral 2:l clay with strongly held water layers in between the platelets. Homoionic Li-saponite is suspended in mixtures of acetonitrile-d3 and heavy water. Reporter quadrupolar nuclei monitor the occurrence of local order. They are *H and I7O for water; 2H and 14N for acetonitrile; and 'Li for the counterions. The residual quadrupolar splittings in the resonances for these nuclei are internally consistent within the molecules. As the acetonitrile content of the binary solvent mixtures is raised, more and more lithium ions are extracted from the Stern into the Gouy-Chapman diffuse layer. Stacks of saponite flakes segregate layers of CD3CN and D20 molecules from one another. At low acetonitrile content (
