Molar heat capacity and thermodynamic properties of Lu(C5H9NO4)(C3H4N2)6(ClO4)3·5HClO4·10H2O

A complex of Lutetium perchloric acid coordinated with l -glutaminic acid (C 5 H 9 NO 4 ) and imidazole (C 3 H 4 N 2 ), Lu(C 5 H 9 NO 4 )(C 3 H 4 N 2 ) 6 (ClO 4 ) 3 ·5HClO 4 ·10H 2 O was synthesized and characterized. Thermodynamic properties of the complex were studied with an adiabatic calorimeter (AC) from 80 to 390 K and differential scanning calorimetry (DSC) from 100 to 300 K. Two thermal abnormalities were discovered at 220.34 and 248.47 K, which were deduced to be phase transitions. One was interpreted as a freezing-in phenomenon of the reorientational motion of ClO 4 − ions and the other was attributed to the orientational order/disorder process of ClO 4 − ions. The low-temperature molar heat capacities were measured by AC and the thermodynamic functions [ H T − H 298.15 ] and [ S T − S 298.15 ] were derived in the temperature range from 80 to 390 K with temperature interval of 5 K. Thermal decomposition behavior of the complex was studied by thermogravimetric analysis and DSC.