Novel sight into Mn(II) complexation with some tri- and tetradentate ligands in aqueous solutions. Specific aspects of interacting with β-aminotricarballylic acid

For the first time the XRD data of β-aminotricarballylic acid (BATCA) hydrochloride crystals are obtained. The acid-base properties of BATCA are presented herein, as compared to aspartic (AA), citric (CA), iminodiacetic (IDA), and nitrilotriacetic (NTA) acids. The comprehensive analysis of composition, pH distribution areas, and stability constants of manganese(II) complexes is carried out from the pH-metric titration and NMR relaxation (0.47 T) experiments at 298 K. Equilibrium constants were obtained using the CPESSP and STALABS computer programs. The approach based on the values of the spin–spin and spin–lattice relaxivities ratio (r2/r1) is used to assess the number of water molecules bound to Mn2+ ion in its complexes in aqueous solutions. This information is useful for prediction of increasing the contrast of MRI-images by manganese(II) complexes, as well as for analyzing the diversity of the complex structures in the solutions