Thermochemistry on the Complex of Erbium Perchlorate with L-α-Glutamic Acid [Er2（L-Glu）2（H2O）6]（ClO4）4·6H2O（s）

A coordination compound of erbium perchlorate with L-α-glutamic acid, Er2（Glu）2（H2O）6]（ClO4）4·6H2O（s）, was synthesized. By chemical analysis, elemental analysis, FTIR, TG/DTG, and comparison with relevant literatures, its chemical composition and structure were established. The mechanism of thermal decomposition of the complex was deduced on the basis of the TG/DTG analysis. Low-temperature heat capacities were measured by a precision automated adiabatic calorimeter from 78 to 318 K. An endothermic peak in the heat capacity curve was observed over the temperature region of 290-318 K, which was ascribed to a solid-to-solid phase transition. The temperature Ttrans, the enthalpy △transHm and the entropy △transSm of the phase transition for the compound were determined to be： （308.73±0.45） K, （10.49±0.05） kJ·mol^-1 and （33.9±0.2） J·K^-1·mol^-1. Polynomial equation of heat capacities as a function of the temperature in the region of 78-290 K was fitted by the least square method. Standard molar enthalpies of dissolution of the mixture 2ErCl3·6H2O（s）＋2L-Glu（s）＋6NaClO4·H2O（s）] and the mixture {Er2（Glu）2（H2O）6]（ClO4）4·6H2O（s）＋6NaCl（s）} in 100 mL of 2 mol·dm^-3 HClO4 as calorimetric solvent, and {2HClO4（1）} in the solution A＇ at T=298.15 K were measured to be, △dHm,1=（31.552±0.026） kJ·mol^-1, △dHm,2 = （41.302±0.034） kJ·mol^-1, and △dHm,3 = （ 14.986 ± 0.064） kJ·mol^-1, respectively. In accordance with Hess law, the standard molar enthalpy of formation of the complex was determined as △fHm-=-（7551.0±2.4） kJ·mol^-1 by using an isoperibol solution-reaction calorimeter and designing a thermochemical cycle.

Thermochemistry on the Complex of Erbium Perchlorate with L-α-Glutamic Acid [Er2（L-Glu）2（H2O）6]（ClO4）4·6H2O（s）

A coordination compound of erbium perchlorate with L‐α‐glutamic acid, Er₂(Glu)₂(H₂O)₆](ClO₄)₄·6H₂O(s), was synthesized. By chemical analysis, elemental analysis, FTIR, TG/DTG, and comparison with relevant literatures, its chemical composition and structure were established. The mechanism of thermal decomposition of the complex was deduced on the basis of the TG/DTG analysis. Low‐temperature heat capacities were measured by a precision automated adiabatic calorimeter from 78 to 318 K. An endothermic peak in the heat capacity curve was observed over the temperature region of 290–318 K, which was ascribed to a solid‐to‐solid phase transition. The temperature T_trans, the enthalpy Δ_transH_m and the entropy Δ_transS_m of the phase transition for the compound were determined to be: (308.73±0.45) K, (10.49±0.05) kJ·mol^?1 and (33.9±0.2) J·K^?1·mol^?1. Polynomial equation of heat capacities as a function of the temperature in the region of 78–290 K was fitted by the least square method. Standard molar enthalpies of dissolution of the mixture 2ErCl₃·6H₂O(s)+2L‐Glu(s)+6NaClO₄·H₂O(s)] and the mixture {Er₂(Glu)₂(H₂O)₆](ClO₄)₄·6H₂O(s)+6NaCl(s)} in 100 mL of 2 mol·dm^?3 HClO₄ as calorimetric solvent, and {2HClO₄(l)} in the solution A' at T=298.15 K were measured to be, Δ_dH_m,1= (31.552±0.026) kJ·mol^?1, Δ_dH_m,2= (41.302±0.034) kJ·mol^?1, and Δ_dH_m,3= (14.986±0.064) kJ·mol^?1, respectively. In accordance with Hess law, the standard molar enthalpy of formation of the complex was determined as Δ_fH^?_m = ? (7551.0±2.4) kJ· mol^?1 by using an isoperibol solution‐reaction calorimeter and designing a thermochemical cycle.