Table 4.

Previously establishedand commonly used organic and amino acid chelate ligands for magnesium complexes. Table includes pKa values for the terminal carboxylic proton (pKa₁) and the amino proton (pKa₂). Backbone protons are displayed as pKa₃. The asterisk (*) represents the secondary pKa of citric acid and malic acid, which have no amino proton—in the case of malic acid, the value is for the terminal carboxylic acid farthest from the backbone alcohol. The hyphen (---) indicates that the specified value does not apply to this specific ligand.

Ligand	pKa1	pKa2	pKa3	Lewis Bases
Orotic Acid	2.83	---	---	1
Mandelic Acid	3.41	---	---	2
Anthranilic Acid	2.14	4.85	---	2
Formic Acid	3.75	---	---	1
Glycine	2.34	9.60	---	2
Malic Acid	3.40	5.11 *	---	3
Maleic Acid	1.83	---	---	2
Aspartic Acid	1.88	9.60	---	3
Glutamic Acid	2.19	9.67	---	3
Citric Acid	3.13	4.76 *	6.40	4