Synthesis and calorimetric study of rare earth complexes [RE(C 3H 7NO 2) 2(C 3H 4N 2)(H 2O)](ClO 4) 3 (RE: Sm, Eu, Dy, Er)

Abstract

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(C 3H 7NO 2) 2(C 3H 4N 2)(H 2O)](ClO 4) 3 (RE: Sm, Eu, Dy, Er) by FT-IR, chemical, elemental and thermal analysis. The enthalpies of dissolution of [2C 3H 7NO 2(s) + 3NaClO 4(s)], [C 3H 4N 2(s) + RECl 3·6H 2O(s)] and [3NaCl(s)], {[RE(C 3H 7NO 2) 2(C 3H 4N 2)(H 2O)](ClO 4) 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, RECl 3·6H 2O(s) + 2C 3H 7NO 2(s) + C 3H 4N 2(s) + 3NaCl(s) = [RE(C 3H 7NO 2) 2(C 3H 4N 2)(H 2O)](ClO 4) 3(s) + 3NaCl(s) + 5H 2O(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, Δ f H m Θ {[Re(C 3H 7NO 2) 2(C 3H 4N 2)(H 2O)](ClO 4) 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.