Phase transitions and molecular motions in a model biomembrane (C12H25NH3)2SnCl6

Two successive phase transitions in bis-n-dodecylammonim hexachlorostannate, (n-C12H25NH3)2SnCl6, were studied by means of 1H NMR. From the temperature dependent dipolar splitting, the low and the high temperature transition were attributed to an order–disorder transition and a conformational transition of the rigid hydrocarbon chain, respectively. The spin-lattice relaxation rate in the low and the intermediate temperature phase was well fitted with four types of molecular motions, and the ammonium group was revealed to dictate the order–disorder transition temperature.