DSC studies on structural phase transitions and molecular motions in some A2MCl4 compounds

Structural phase transitions and molecular motions in (CH3NH3)2CoCl4, (C5H5NH)2ZnCl4, and [(CH3)3CNH3]2ZnCl4 were investigated by differential scanning calorimetry (DSC) between about 130 K and the melting points. All of the compounds showed at least one structural phase transition over the temperature region investigated. The values of the transition entropies obtained suggest that most of the transitions are of the order‐disorder type. From these entropy values, thermal motions of the molecules in the highest‐temperature solid phases were inferred. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)