Dependence of the local structure and dynamic behavior of hydration water in (+/-)-[Co(en)(3)]Cl-3.nD(2)O crystal (0 less than or equal to n less than or equal to 4) on the dehydration process was studied by means of H-1 magic-angle sample spinning (MAS) NMR technique. The line shape in the H-1 MAS NMR spectrum depends strongly on the water content (n). For n < 1.5, the spectrum consists mainly of two peaks whose relative intensities change with n, suggesting that the hydration water forms two different types of domainlike structures at room temperature. In addition, the full width at half-maximum of each component of the doublet was less than 1 ppm at room temperature, implying that the water moves rapidly enough to reduce the intermolecular H-1-H-1 dipole interaction. On cooling, the resonance line broadens and its line width exceeds 10 ppm below 200 K where the components of the doublets cannot be discerned. This aspect suggests that the water molecule undergoes slower motion than the MAS rate (5.0-7.0 kHz). The temperature dependence of the line width was analyzed by assuming the Davidson-Cole's spectral density. The activation energy (E-a) for the molecular motion of the water depends drastically on the water content: E-a assumes the constant value of 24 kJ mol(-1) for n less than or equal to 2.1, but it decreases continuously for n > 2.1 and reaches 18 kJ mol(-1) at n = 4. This finding suggests that the molecular motion of hydration water in the pore, which averages out the dipolar interaction between a trace amount of HDO and the protons on the pore wall, changes from whole molecular translational jump to proton migration through hydrogen bond accompanied by molecular reorientation.