Coordination of metronidazole to Cu(II): Structural characterization of a mononuclear square-planar compound

• A copper complex of the anti-parasitic drug metronidazole (MET) was prepared.
• Cu(MET)2Cl2 is the first example of a mononuclear copper–MET compound.
• Copper is square planar with trans arrangements of both Cl and MET ligands.
• The complex exhibits intermolecular Cu⋯O and Cu⋯Cl interactions.

The reaction between metronidazole [1-(2-hydroxyethyl)-2-methyl-5-nitroimidazole, MET] and CuCl2⋅2H2O in methanol solution has allowed isolation of blue crystals of composition Cu(MET)2Cl2⋅MeOH. These crystals have been shown by X-ray diffraction to consist of mononuclear square-planar trans-Cu(MET)2Cl2 molecules in which the metronidazole ligands are trans to each other, as are the Cl ligands. The structure of this compound is very different from other compounds that have been obtained from the reaction between CuCl2⋅2H2O and metronidazole, namely [Cu(MET)2(μ-Cl)Cl]2 and [Cu(MET)2(μ-Cl)(OH2)]2[Cl]2, which are dimers featuring bridging chloride ligands.

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