Calorimetric study and thermal analysis of [Ho-2(Ala)(4)(H2O)(8)]Cl-6 and [ErY(Ala)(4)(H2O)(8)] (ClO4)(6)

Two solid complexes of rare-earth compounds with alanine, [ho2(ala)(4)(h2o)(8)] cl-6 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)] cl-6 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)] cl-6, 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)] cl-6; 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 similar to 800 degreesc by using the thermogravimetric and differential thermogravimetric (tg/dtg) analysis techniques. the tg/dtg curves showed that the decomposition started from 80 degreesc and ended at 479 degreesc, completed in two steps for [ho2 (ala)(4) (h2o)(8)]cl-6, and started from 120 degreesc and ended at 430 degreesc, completed in three steps for [ery(ala)(4) (h2o)(8)] (clo4)(6), respectively. the possible mechanisms of the thermal decompositions were elucidated.