Thermodynamic properties and molar heat capacity of Er2(Asp)2(Im)8(ClO4)6·10H2O
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A complex of Erbium perchloric acid coordinated with l-aspartic acid and imidazole, Er2(Asp)2(Im)8(ClO4)6·10H2O was synthesized for the first time. It was characterized by IR and elements analysis. The heat capacity and 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. Glass transition and phase transition were discovered at 220.45 and 246.15 K, respectively. The glass transition was interpreted as a freezing-in phenomenon of the reorientational motion of ClO4− ions and the phase transition was attributed to the orientational order/disorder process of ClO4− ions. 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 in nitrogen atmosphere was studied by thermogravimetric (TG) analysis and differential scanning calorimetry (DSC).
KeywordsEr2(Asp)2(Im)8(ClO4)6·10H2O Adiabatic calorimetry Low-temperature heat capacity Glass transition Phase transition Thermal analysis
This study was financially supported by the National Nature Science Foundation of China under the NSFC Grant No. 21003069, 21073189.
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