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Low-temperature heat capacity and thermodynamic properties of crystalline [Re2(Ala)4(H2O)8](ClO4)6 (Re = Eu, Er; Ala = alanine) |
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| Authors: | Beiping Liu Zhi-Cheng Tan Dashun Zhang Zhaodong Nan Lixian Sun Fen Xu Xiaozhen Lan Ping Liang Xiaomei Yu |
| Institution: | a Department of Chemistry, Changde Normal College, Changde 415000, China b Thermochemistry Laboratory, Dalian Institute Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China c State Key Laboratory of Fine Chemical, Dalian University of Technology, Dalian 116012, China |
| Abstract: | Re2(Ala)4(H2O)8](ClO4)6 (Re=Eu, Er; Ala=alanine) were synthesized, and the low-temperature heat capacities of the two complexes were measured with a high-precision adiabatic calorimeter over the temperature range from 80 to 370 K. For Eu2(Ala)4(H2O)8](ClO4)6, two solid–solid phase transitions were found, one in the temperature range from 234.403 to 249.960 K, with peak temperature 243.050 K, the other in the range from 249.960 to 278.881 K, with peak temperature 270.155 K. For Er2(Ala)4(H2O)8](ClO4)6, one solid–solid phase transition was observed in the range from 270.696 to 282.156 K, with peak temperature 278.970 K. The molar enthalpy increments, ΔHm, and entropy increments,ΔSm, of these phase transitions, were determined to be 455.6 J mol?1, 1.87 J K?1 mol?1 at 243.050 K; 2277 J mol?1, 8.43 J K?1 mol?1 at 270.155 K for Eu2(Ala)4(H2O)8](ClO4)6; and 4442 J mol?1, 15.92 J K?1 mol?1 at 278.970 K for Er2(Ala)4(H2O)8](ClO4)6. Thermal decompositions of the two complexes were investigated by use of the thermogravimetric (TG) analysis. A possible mechanism for the thermal decomposition is suggested. |
| Keywords: | Alanine rare earth compounds Heat capacity Thermal decomposition Adiabatic calorimeter TG analysis |
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