Synthesis, crystal structures and IR spectra of isotypic pseudopolymorphs complexes of Zn(II) by indole-2-carboxylic acid and 2,9-dimethyl-1,10-phenanthroline with different solvates (DMA, DMF or DMSO)

Three ternary complexes of zinc indole-2-carboxylate (2-IC) with 2,9-dimethyl-1,10-phenanthroline (NC) in dimethylacetamide (DMA), dimethylformamide (DMF) or dimethyl sulfoxide (DMSO) were synthesized, their X-ray crystal structure and IR spectra were determined. In compound [Zn(2-IC)2(NC)]·(DMA) (1), Zn is five-coordinate by one bidentate NC ligand and two 2-IC anionic ligands one of which is monodentate, and the other is bidentate. The individual molecules are linked into chains running parallel to the a-axis by intermolecular hydrogen bonding. The crystal structure is completed by a DMA solvate molecule. Compounds [Zn(2-IC)2(NC)]·(DMF) (2) and [Zn(2-IC)2(NC)]·(DMSO) (3) contain one monomeric zinc complex similar to 1 and a disordered solvate molecule (DMF in 2; DMSO in 3) in contrast to 1. In the IR spectra of the three compounds, the most important feature is the appearance of a very broad band at about 3175 cm−1 presenting a fine structure which can be correlated to hydrogen bonds in N-H⋯O bifurcated links, via inter and intramolecular interactions. A tentative assignment was made to point out the bidentate or monodentate carboxylate groups attached to the Zn atom.