Metal Ion Complexes of Aromatic Amino Acids

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Abstract
This study has shown that certain ring substitutions on aminobenzoic acids are possible without greatly affecting the favorable chelating properties of the parent ligand. It was also shown that para substitution of methyl groups yields more stable complexes than does ortho substitution relative to the amino group. Meta substitution of chlorine enhances chelate formation and yields very insoluble complexes in yields approaching one hundred per cent. Based on carbon-hydrogen analyses and other analytical data, the structures have been determined as square planar ones in which the ligand functions as a bidentate. Some water is usually incorporated in the crystal lattice, and occasionally a complex will contain one or more molecules of coordinated water. The variable amount of water in some compound crystals makes the carbonhydrogen data less exact and tends to obscure interpretation of at least some of the infrared data. Lack of solubility in water and in other polar and nonpolar solvents increases the difficulty of both infrared and ultraviolet-visible analyses; in every case potassium bromide tablets were made and were used in both infrared and ultraviolet-visible spectrophotometers; evidence obtained through study of the ultraviolet-visible data are not presented here, but there substantiate the data obtained by the other methods. With the ligands and metal cations used, fifty-five compounds were possible; forty-four of these were actually prepared and isolated, and of these, thirty-five were shown to be coordination complexes. Twenty-seven of these complexes were previously unreported including all the compounds reported for 3,5-dimethylanthranilic acid, 2-amino-4-chlorobenzoic acid, and 6-amino-3-methylbenzoic acid.

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