The coordination properties of aminobenzoate ligands in complexes with alkali metals

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.