Proton magnetic relaxation in crystalline amminoacetate Zn(2) and Cd(2) complexes

The proton spin-lattice relaxation time is measured vs. temperature in Cd(NH3)4 x (CH3COO)2 -I and Zn(NH3)2(CH3COO)2-II. The activation energies for NH3 reorientation, as well as T sub(1 min), are determined for the two compounds, respectively, as: Esub(α)sup(I) = 4.4 kcal/mole, Tsub(1 min)sup(I) = 94 ms; Esub(α)sup(II) = 4.2 kcal/mole, Tsub(1 min)sup(II) = 280 ms. These results suggest that, in (I), all the coordinated NH3 molecules take part in the relaxation process, whereas in (II) - but one of the two. (author)