Acta Phys. -Chim. Sin. ›› 2002, Vol. 18 ›› Issue (06): 481-485.doi: 10.3866/PKU.WHXB20020601

• Communication •     Next Articles

Calorimetric Study and Thermal Analysis of [Ho2(Ala)4(H2O)8]Cl6 and >;[ErY(Ala)4(H2O)8](ClO4)6

Liu Bei-Ping;Tan Zhi-Cheng;Nan Zhao-Dong;Liu Ping;Sun Li-Xian;Xu Fen   

  1. Thermochemistry Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023;Department of Chemistry, Changde Normal College, Changde 415000
  • Received:2002-01-28 Revised:2002-03-26 Published:2002-06-15
  • Contact: Tan Zhi-Cheng

Abstract: Two solid complexes of rare-earth compounds with alanine, [Ho2(Ala)4(H2O)8]Cl6 and [ErY(Ala)4(H2O)8](ClO4)6 (Ala=alanine) were synthesized,and a calorimetric study and thermal analysis for the two complexes were performed through adiabatic calorimetry and thermogravimetry. The low-temperature heat capacities of [Ho2(Ala)4(H2O)8]Cl6 and [ErY(Ala)4(H2O)8](ClO4)6 were measured with an automated adiabatic precision calorimeter over the temperature range from 78 to 377 K. Solid-solid phase transitions were found between 214 K and 255 K with a peak temperature of 235.09 K for [Ho2(Ala)4(H2O)8]Cl6,between 99 K and 121 K with a peak temperature of 115.78 K for [ErY(Ala)4(H2O)8](ClO4)6.The enthalpies and entropies of the phase transitions were determined to be 3.02 kJ•mol-1,12.83 J•K-1•mol-1 for [Ho2(Ala)4(H2O)8]Cl6; 1.96 kJ•mol-1,16.90 J•K-1•mol-1 for [ErY(Ala)4(H2O)8](ClO4)6, respectively. Thermal decomposition of the two complexes were investigated in the temperature range of 40~800 ℃ by using the thermogravimetric and differential thermogravimetric (TG/DTG ) analysis techniques. The TG/DTG curves showed that the decomposition started from 80 ℃ and ended at 479 ℃,completed in two steps for [Ho2(Ala)4(H2O)8]Cl6,and started from 120 ℃ and ended at 430 ℃,completed in three steps for [ErY(Ala)4(H2O)8](ClO4)6,respectively.The possible mechanisms of the thermal decompositions were elucidated.

Key words: [Ho2(Ala)4(H2O)8]Cl6, [ErY(Ala)4(H2O)8](ClO4)6, Adiabatic calorimetry, Heat capacity, Thermal decomposition