Solution-reaction Calorimetric Study of Coordination Compounds of Rare Earth Perchlorates with Alanine and Imidazole

Two coordination compounds of rare earth perchlorates with alanine and imidazole, [RE(Ala)n(Im)(H2O)]- (ClO4)3(s) (RE=La, n=3; RE=Nd, n=2), have been prepared and characterized. The standard molar enthalpies of reaction for the following two reactions, LaCl37H2O(s)+3Ala(s)+Im(s)+3NaClO4(s)=[La(Ala)3(Im)(H2O)]- (ClO4)3(s)+3NaCl(s)+6H2O(l) (1) and NdCl36H2O(s)+2Ala(s)+Im(s)+3NaClO4(s)=[Nd(Ala)2(Im)(H2O)]- (ClO4)3(s)+3NaCl(s)+5H2O(l) (2), were determined by solution-reaction calorimetry, at T=298.15 K, as 36.168±0.642 kJmol-1 and 48.590±0.934 kJmol-1 respectively. From the results and other auxiliary quantities, the standard molar enthalpies of formation of [La(Ala)3(Im)(H2O)](ClO4)3(s) and [Nd(Ala)2(Im)(H2O)] (ClO4)3(s) were derived, fmHD!{[La(Ala)3(Im)(H2O)](ClO4)3, s}=(-2984.8±1.0) kJmol-1 and fmHD! {[Nd(Ala)2(Im)(H2O)]- (ClO4)3, s}=(-2387.8±0.8) kJmol-1 , respectively.