“…Rotations in [Ni(NH 3 ) 6 ]X 2 crystals (X = Cl, Br, I) have been studied by EPR, − and observed line-width variations have been explained in terms of correlated rotations of the NH 3 groups . Trapp and Shyr proved this by looking at the EPR spectra of [Ni(NH 3 ) 6 ]X 2 in [Zn(NH 3 ) 6 ]X 2 and [Cd(NH 3 ) 6 ]X 2 hosts (where X = Cl, Br, I). Above the critical temperature ( T c ), the complexes existed in a perfectly octahedral environment, and below the T c , the motion is frozen.…”