Y. Di, Z. Tan
2007
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Journal
Acta Chimica Slovenica
Abstract
A coordination compound of erbium perchlorate with L-α-glycine, [Er 2 (Gly) 2 (H 2 O) 12 ] (ClO 4 ) 6 · 4H 2 O(s), was synthesized. By chemical analysis, elemental analysis, FTIR, TG/DTG, and comparison with relevant literature, its chemical composition and structure were established. The purity was found to be >99.0%, without melting point. Low-temperature heat capacities were measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 372 K. An obvious endothermic peak in the heat capacity curve was observed over the temperature region of 275-296 K, which was ascribed to a solid-to-solid phase transition according to the results of TG/DTG analysis. The temperature T tr , the enthalpy Δ tr H m and the entropy Δ tr S m of the phase transition for the compound were determined to be, T trs = (283.315 ± 0.061) K, (11.026 ± 0.059) kJ mol -1 and (38.918 ± 0.206) J K -1 mol -1 . Two polynomial equations of heat capacities as a function of the temperature in the regions of 78-275 K and 296-372 K were fitted by the least square method, respectively. The mechanism about thermal decomposition of the complex was deduced on the basis of the TG/DTG analysis. In accordance with Hess law, the standard molar enthalpy of formation for the complex was determined as Δ f H o m = -(7794.40±1.01) kJ mol -1 , by an isoperibol solution-reaction calorimeter.