X-Ray Structures of Three Polymeric and Two Mononuclear Metal Complexes on the Base of p-Aminobenzoic Acid

Abstract

Crystals of five coordination compounds have been grown from solutions containing p-aminobenzoic acid (PABA), diethanolamine (DEA) and salt of the definite metal. The X-ray crystallography attests that complexes [Co(PABA)2(H2O)2]n·H2O (1), [Ni(PABA)2(H2O)2]n·H2O (1′) and [Zn(PABA)2(H2O)]n·H2O (2) are polymeric, while Mn(DEA)2·2(PABA)·2(H2O) (3) and Cr(DEA)2·2(PABA) (4) are mononuclear coordination compounds. In the isomorphic polymers 1 and 1′ metal ions are bridged to infinite columns by coordination bonds of the two antiparallel PABA molecules (bimolecular association). The complex 2 is 2-D polymer repeating units of which are hexagons generated by combination of mono- and bimolecular associations. All six coordination sites of Mn2+- and Cr2+-ions in 3 and 4 are occupied by two DEA molecules retaining PABA anions in outer sphere. The CSD analysis shows that there are five types of coordination polymers bridged by O and N atoms of the PABA-molecules. As a result of this research two new type motif polymers have been added to the existing list.