Synthesis and structure of trans-bis(4-amino-3-nitrobenzoato-κO)bis(4-amino-3-nitrobenzoic acid-κO)diaquamanganese(II) dihydrate

Abstract

The manganese title complex, [Mn(C7H5N2O4)2(C7H6N2O4)2(H2O)2]·2H2O, is one of the first 4-amino 3-nitrobenzoic acid (4 A3NBA) monoligand metal complexes to be synthesized. It crystallizes in the centrosymmetric monoclinic space group P21/n with the complex molecules located on inversion centers. Four 4 A3NBA ligand molecules are monodentately coordinated by the Mn2+ ion through the carboxylic oxygen atoms while the other two positions of the inner coordination sphere are occupied by water molecules, giving rise to a distorted octahedron, and two water molecules are in the outer coordination sphere. There are two intramolecular hydrogen bonds in the complex molecule. The first is of the common N—H...O=N type, while the second is a rarely occurring very strong hydrogen bond in which a common proton is shared by two uncoordinated oxygen atoms of neighboring carboxylate groups. In the crystal, an intricate system of intermolecular hydrogen bonds links the complex molecules into a three-dimensional-network.