The coordination properties of aminobenzoate ligands in complexes with alkali metals

Abstract

The crystal structures of sodium 4-amino-2-hydroxybenzoate dihydrate [NaL·2H₂O, L = C₆H₃(NH₂)(OH)COO] and potassium 2-aminobenzoate monohydrate [KL*·H₂O, L* = C₆H₄(NH₂)COO] were determined by X-ray diffraction methods. The compound NaL·2H₂O crystallizes in the monoclinic system, space group P2₁/c with a = 8.820(2), b = 14.632(3), c = 6.948(2) Å, β = 97.88(3)°. The structure consists of sodium ion pairs joined together by tridentate 4-amino-2-hydroxybenzoate moieties creating a polymeric chain. In the metal centres, two water molecules bridge the sodium atoms. Five oxygen atoms and one nitrogen atom form a distorted octahedral environment. The compound KL*·H₂O crystallizes in the monoclinic system, space group P2₁/c with a = 14.684(3), b = 7.618(2), c = 7.512(2) Å, β = 96.95(3)°. The structure consists of octacoordinated potassium atoms bonded with three water molecules and five carboxylate oxygen atoms. Water molecules appear as bridging ligands. The 2-aminobenzoate ligand acts as a pentadentate ligand with the molecular network stabilized by hydrogen bonds. Among the polymeric chains in both structures appear noncovalent interactions of type N−H···X.

Keywords:

• Sodium 4-amino-2-hydroxybenzoate
• Potassium 2-aminobenzoate
• Crystal structure