Abstract: The mechanism of the solid-solid phase transition in the perovskite-type layer of the title complex has been studied by infrared spectroscopy.The phase transition is related to the structural change of alkyl chains and it is mainly arises from the change of the packing structure and conformational order-disorder change in the alkyl chains.The phase transition is accompanied by an obvious decrease of the hydrogen bond strength.The "melting"of the chains occurs owing to the TG defects near the terminal groups and GTG+GTG',as well as GG defects at higher temperature,It is found that the frequencies of an in-phase and an out-of-phase streching of C-C bonds are sensitive to the phase transition of the"chain melting".

Key words: dodecylammonium tetrachlorozincate, phase transition, molecular conformation, infrared spectroscopy