Two supramolecular complexes based on 4-hydroxybenzoic acid and triethanolamine: Synthesis and structure

Two new copper and nickel complexes with triethanolamine (TEA) and 4-hydroxybenzoic acid (L) have been synthesized within the framework of systematic studies into the formation of mixed-ligand metal complexes on the basis of commercially available compounds with the simplest structure, such as ethanolamines and benzoic acid monoderivatives (hydroxy-, amino-, and nitrobenzoic acids). According to X-ray diffraction data, the complexes have the compositions [Cu2(L)2(TEA)2] · [Cu(TEA)2] · 2H2O (I) and [Ni(TEA)2] · 2L (II). Compound I is a mixed-ligand complex, while complex II is a supramolecular compound consisting of a nickel–TEA monoligand complex anion and non-coordinated L. TEA molecules in complex I are coordinated in both tetradentate and tridentate mode, while only tridentate coordination is typical for complex II. The coordination polyhedra of metal atoms are tetragonal bipyramids elongated due to the Jahn–Teller effect in complex I and octahedra in complex II. In both crystals, structural units are linked into 2D associates via hydrogen bonds.