Synthesis and calorimetric study of rare earth complexes [RE(C3H7NO2)2(C3H4N2)(H2O)](ClO4)3 (RE: Sm, Eu, Dy, Er)

The crystals of four complexes of rare earth perchlorate with dl-α-alanine and imidazole were synthesized and characterized. The components of them were determined to be [RE(C3H7NO2)2(C3H4N2)(H2O)](ClO4)3 (RE: Sm, Eu, Dy, Er) by FT-IR, chemical, elemental and thermal analysis. The enthalpies of dissolution of [2C3H7NO2(s) + 3NaClO4(s)], [C3H4N2(s) + RECl3·6H2O(s)] and [3NaCl(s)], {[RE(C3H7NO2)2(C3H4N2)(H2O)](ClO4)3(s)} were determined by a solution–reaction isoperibol calorimeter at T=298.15 K, respectively. According to Hess’s law, the standard molar enthalpies of reaction of four reactions, RECl3·6H2O(s) + 2C3H7NO2(s) + C3H4N2(s) + 3NaCl(s) = [RE(C3H7NO2)2(C3H4N2)(H2O)](ClO4)3(s) + 3NaCl(s) + 5H2O(l) (RE: Sm, Eu, Dy, Er) were determined to be 4.87±0.20, 7.23±0.19, 0.96±0.27 and 12.88±0.32 kJ mol−1, respectively. The standard molar enthalpies of formation of the four complexes at T=298.15 K, ΔfHmΘ {[Re(C3H7NO2)2(C3H4N2)(H2O)](ClO4)3(s)} (RE: Sm, Eu, Dy, Er), were determined to be −(2448.1±3.3), −(2360.3±3.3), −(2451.8±3.3) and −(2444.3±3.3) kJ mol−1, respectively.