Metal coordination compounds derived from tinidazole and transition metals. Halogen and oxygen lone pair···π interactions

The crystal structures of four metal coordination compounds derived from CuCl2, ZnCl2 or ZnBr2 and 1-(2-ethylsulfonylethyl)-2-methyl-5-nitro-imidazole (tinidazole) are reported. The polyfunctional and enatiomerically pure ligand gave place to metal coordination compounds bearing two halogen atoms and two ligands bound by the imidazole nitrogen atom. Two conformers were isolated from the reaction with CuCl2. One is the kinetic product (1) with two ligands where the flexible chain is in an extended conformation. The second is the thermodynamic compound (2) which has a folded conformation in one of its ligand. The stabilization of the folded conformation was due to two intramolecular SO oxygen atom interactions with the imidazolic rings, as was observed in the X-ray diffraction analysis and confirmed by calculations. Comparison between the X-ray diffraction structure of the free ligand with its imidazolium hydrochloride showed that the decrease of the electronic density of the ring favors the SO oxygen contacts. Reactions with ZnCl2 and ZnBr2 afforded only the folded conformers (3 and 4) were isolated. In compound 1 the extended arms give a V shape which favors the chloro atoms contact in the inner side of the imidazole rings forming ribbons, which in turn are held together by hydrogen bonds forming pleated sheets. In compound 2, the folded ligand inhibits the intermolecular contacts with the internal side; therefore the molecules are alternate and coupled by π-contacts by their external surfaces forming a ribbon. The ribbons give place to hexagonal assemblies creating channels. Compounds 1–4 present diverse intra- and intermolecular short stabilizing contacts between halogen and oxygen atoms and the imidazole ring electronic system.

Metal organic coordination compounds from CuCl2 or ZnX2 and tinidazole were synthesized. The [Cu(tnz)2Cl2] compounds presented two conformers, the kinetic one has extended ligands while the thermodynamic presents a folded ligand with SO···imidazole interactions. Calculations showed that the folded structure is more stable than the extended one, due to the electroaccepting properties of the imidazole ring promoted by coordination of the metal ion or by protonation. The coordination compounds present different metal organic compounds, with several π contacts: C···C, Cl···π, Br···π, SO···π and hydrogen bonding.Figure optionsDownload as PowerPoint slide