132758-90-8Relevant articles and documents
Steric factors and stability of the complexes of pyridinecarboxylate ions with group IIA cations. A thermodynamic study
Aruga, Roberto
, p. 79 - 82 (2007/10/02)
Heats and entropies of complex formation of 2-pyridinecarboxylate and 2,6-pyridinedicarboxylate with Mg(II), Ca(II), Sr(II) and Ba(II) cations were determined by direct calorimetry, and using the stability constants in the literature.The measurements were carried out in aqueous solution at 25 deg C and I = 0.2 mol.l(-1) (NaNO3).Examination of the results shows that the cause of the comparatively high stability of the complexes of pyridinecarboxylic ligands with group IIA cations is enthalpic.This is probably due to the coplanar position of the pyridine ring and the carboxylic groups.This factor acts more strongly in the case of Ca, Sr and Ba than of Mg, probably for reasons connected with the cation dimension.The different order of stability of the Mg and Ca complexes with the present ligands is probably due to the same cause.