Dynamic Behavior of H_2O Molecules in [Pt(en)_2] [PtX_2(en)_2] (SO_4)_2・6H_2O Studied by ^2H and ^1H NMR

We measured the temperature dependences of ^2H NMR spectra and ^1H spin-lattice relaxation time (T_1) in [Pt (en)_2] [PtX_2(en)_2] (SO_4)_2・6H_2O (X:Cl and I). The obtained ^2H NMR spectra and ^1H T_1 at T>250K were attributable to the 180°flip motion of the water molecule. The activation energy and the correlation time at infinite temperature for the 180°flip of H_2O were evaluated to be Ea=27 kJ mol^<-1> and τ_0=1.0×10^<-13>s, respectively. These results suggest that the network of the hydrogen bond through H_2O molecules is strongly linked in the crystal.