MOLECULAR-MOTION IN SOLID TETRAETHYLAMMONIUM AND TETRABUTYLAMMONIUM PERCHLORATES

The proton NMR second moment and spin-lattice relaxation time for poly crystalline tetraethyl- and tetrabutylammonium perchlorates have been measured over a wide range of temperatures. Solid-solid phase transiti ons related to the onset of cation tumbling were found for both compou nds and confirmed by DSC. In the low temperature phases methyl-group r eorientation was evidenced. For tetrabutylammonium cation a dynamic no nequivalence of one methyl group is found. The geared motion of the al kyl chains related with the onset of successive CH2-group reorientatio ns is suggested.