Synthesis and Thermochemical Properties of New Ternary Lanthanum Complex La(Glu)(Im)(6)(ClO4)(3)center dot 4HClO(4)center dot 4H(2)O

A new ternary lanthanurn complex, La(Glu)(Im)(6)(ClO4)(3)center dot 4HClO(4)center dot 4H(2)O (Glu: glutamic acid, Im: imidazole), was synthesized and its thermodynamic properties were studied. Heat capacities of the complex were measured with a high-precision automatic adiabatic calorimeter over a temperature range from 80 to 390 K and the thermodynamic functions (H-T-H-298.15) and (S-T-S-298.15) were derived from the heat capacity data with a temperature interval of 5 K. Glass and phase transitions of the new complex at around 216 and 246 K were observed both by adiabatic calorimetry and differential scanning calorimetry (DSC) analyses. Thermodynamic data of the phase transitions were calculated and the transition mechanism was determined to be a 're-orientational process of the perchlorate ions in the complex. The thermal stability of the complex was tested by the thermogravimetric (TG) technique and a possible mechanism for its decomposition was proposed