Fig. 5. Alkaline earth metal complexes of macropa-β-alanine. (a) Species distribution diagrams of macropa (left) and macropa-β-alanine (right) in the presence of Ba²⁺ at [Ba²⁺]_tot = [L]_tot = 1.0 mM, I = 0.1 M KCl, and 25 °C. (b) X-ray crystal structure of [Ba(macropa-β-alanine)(DMSO)]. Ellipsoids are drawn at the 50% probability level. Nonacidic hydrogen atoms are omitted for clarity. A full discussion of the crystallographic disorder of the structure is provided in the ESI.† (c) Comparison of the immediate coordination sphere of the Ba²⁺ center in the crystal structures of [Ba(Hmacropa)(DMF)]⁺ and [Ba(macropa-β-alanine)(DMSO)].