The motion of water in the galleries of layered Cd0.75PS3K0.5(H2O)1.2, prepared by the ion-exchange intercalation of hydrated potassium ions into CdPS3, have been investigated using a combination of orientation dependent NMR and infrared (IR) spectroscopies as a function of temperature. Within the galleries of the intercalated compound the potassium ions are displaced toward the layers and are immobile, while the water molecules form monolayer-thick two-dimensional islands. Two types of interlamellar water are distinguishable by both NMR and IR spectroscopy. A loosely bound isotropically tumbling water which is easily lost on mild evacuation and a more tightly bound water with restricted degrees of rotational freedom. The angular dependence of the NMR and IR spectral features of the latter indicate that their C⃗ 2 symmetry axis is at a fixed orientation with respect to the interlamellar normal and rotate rapidly about it. In analogy with bulk aqueous solutions these two types of interlamellar water may be considered as two-dimensional solventlike water and water coordinated to the potassium ion forming part of its hydration shell. A remarkable feature of the water in the galleries of Cd0.75PS3K0.5(H2O)1.2 is the extremely slow rate of exchange (τ ≫ 10-5 s) between the two-dimensional solventlike water and the coordinated water, in direct contrast to the rapid exchange observed for K ions in bulk aqueous solutions. The present experimental results provide the first observation of the effect of confinement on solvation shell exchange. It is suggested that the slowing down could be the effect of confinement in two dimension which would strongly inhibit any mechanism involving transition or intermediate states which require an expansion of the coordination shell around the potassium ion.

The motion of hydrated Na ions in the galleries of layered Cd 0.75 PS 3 Na 0.5 ͑H 2 O͒ 2 have been investigated by proton and 23 Na NMR and impedance measurements as a function of temperature. The material is conducting and the frequency dependent conductivity exhibits a power law characteristic of non-Debye-like electrical conductivity relaxation, arising from Coulomb correlation among charge carriers. The NMR spectra indicates that the interlamellar Na ions are mobile and there is good agreement between the 23 Na spin-lattice relaxation rates and the electrical conductivity relaxation. The proton NMR exhibits a well resolved orientation dependent dipolar splitting which has been rationalized by considering the anisotropic rotational motion of water molecules in the pseudo-octahedral hydration shell of the Na ion. Isotropically tumbling water as well as proton hopping among water molecules is absent in Cd 0.75 PS 3 Na 0.5 ͑H 2 O͒ 2. Evidence is presented to show that within the galleries the Na ion moves along with its hydration shell, the motion being such that the orientation of the C ជ 2 axis of the water molecule with respect to the normal to the layers is always preserved. The motion of the hydrated Na ions are correlated through their mutual Coulombic interaction but the rotational motion of the water molecule in the ions hydration shell may still be described by a single exponential Debye-like relaxation.

Lithium ions solvated by polyethylene-oxide ͑PEO͒ have been confined by intercalation within the galleries of an insulating, inorganic layered solid CdPS 3. The dc conductivity of this confined polymer electrolyte Cd 0.75 PS 3 Li 0.5 (PEO) displays a distinct change in the mechanism of conduction with temperature, exhibiting a crossover from an Arrhenius temperature dependence at low temperatures to an non-Arrhenius, Vogel-Tamman-Fulcher behavior at higher temperatures. We use 2 H, 7 Li, and 13 C nuclear magnetic resonance ͑NMR͒ in combination with infrared spectroscopy to probe Li ion mobility as well as segmental motion of the intercalated PEO. Within the galleries of Cd 0.75 PS 3 Li 0.5 (PEO) both rigid and mobile fractions of the intercalated polymer are present with the equilibrium fraction of the mobile species increasing with temperature. The 7 Li (Iϭ3/2) NMR of the confined polymer electrolyte exhibits an unusual behavior-the appearance of quadrupolar satellites at high temperatures where the conductivity values are appreciable. The results signify the solvation of Li ions by mobile segments of the intercalated PEO. Further proof of this association is seen in the 13 C NMR as well as infrared spectra, both of which show evidence of the complexation of Li ions by ether linkages of the interlamellar PEO at high temperature and the absence of such an association at lower temperature when polymer motion is absent.

The 7 Li nuclear magnetic resonance spectra and spin-lattice relaxation rates of lithium ions in an intercalated polymer electrolyte, Li-polyethylene-oxide confined within the galleries of an inorganic layered solid CdPS 3 , are reported. The spectra show an unusual feature, the appearance above 330 K of quadrupolar satellites, whose splitting increases linearly with temperature, and their absence below this temperature. This behavior is also reflected in the temperature variation of the spin-lattice relaxation rates, which show a minimum at 300 K but above 330 K start decreasing again. Using an anisotropic quantum oscillator model, the observed variation in the 7 Li quadrupolar coupling constant is shown to arise from changes in the time average of the electric field gradient as seen by a 7 Li nucleus associated with mobile segments of the intercalated polymer.

Hydrated Na ions have been ion-exchange intercalated into layered cadmium thiophosphate to give Cd 0.75 PS 3 Na 0.5 (H 2 O) y . Two stable phases with y ) 1 and 2 are obtained with lattice expansion 2.8 and 5.6 Å, respectively. The former phase is formed from the y ) 2 phase either by evacuation or heating. The effect of the extent of hydration on the motion of interlamellar water has been investigated by analyzing the dipolar splittings observed in the 1 H NMR spectrum as the system transforms from the y ) 2 phase to the y ) 1 phase. In the y ) 2 phase the water molecules rotate about the interlamellar normal, C B*, as well as about their C B 2 symmetry axis. On formation of the y ) 1 phase there is partial loss of rotational freedom; rotational motion about the C B 2 axis of the interlamellar water is now no longer present. We propose a simple electrostatic model to explain these results.