Deuterium NMR study of molecular dynamics and phase transition in acetonitrile crystal.
The molecular dynamics and local structure in the alpha and beta phases of CD(3)CN were studied by (2)H NMR spectroscopy. From the (2)H NMR spin-lattice relaxation time (T(1)), the activation energies of the rotation of the CD(3) group about the C(3) axis in both phases were found to be 6.2 and 11 kJ mol(-1), respectively. These activation energy values suggest that the packing between CD(3)CN molecules in the alpha phase is weaker than that in the beta phase. The slow structural change of the crystal due to the alpha-beta phase transition was investigated using the (2)H NMR spectra and T(1). A jump of CH(3)CN between two neighboring sites in the hydrogen-bond network accompanying the molecular reorientation was observed by the (2)H NMR 2D exchange spectra and the stimulated-echo method in the alpha phase. Vacancy diffusion occurred in the one-dimensional hydrogen-bond network in the alpha phase.
Suzuki
You
Y
Department of Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan.
Sato
Masato
M
Takanohashi
Kazuyoshi
K
Ida
Tomonori
T
Mizuno
Motohiro
M