MOLECULAR-MOTION IN SOLID TETRAETHYLAMMONIUM AND TETRABUTYLAMMONIUM PERCHLORATES

The proton NMR second moment and spin-lattice relaxation time for polycrystalline tetraethyl- and tetrabutylammonium perchlorates have been measured over a wide range of temperatures. Solid-solid phase transitions related to the onset of cation tumbling were found for both compounds and confirmed by DSC. In the low temperature phases methyl-group reorientation was evidenced. For tetrabutylammonium cation a dynamic nonequivalence of one methyl group is found. The geared motion of the alkyl chains related with the onset of successive CH2-group reorientations is suggested.