Synthesis, crystal structure, catalytic and anti-Trypanosoma cruzi activity of a new chromium(III) complex containing bis(3,5-dimethylpyrazol-1-yl)methane

The reaction of CrCl₃6H₂O with the ligand bis(3,5-dimethylpyrazol-1-yl)methane (L) yielded the cationic complex [(Cr(L)(H₂O)₂Cl₂]⁺, which crystallized as the chloride trihydrate [(Cr(L)(H₂O)₂Cl₂]Cl·3H₂O. The chromium complex was characterized by elemental analysis, electrical conductivity, Infrared and Ultraviolet/Visible spectroscopy. The crystal structure determination using single-crystal X-ray diffraction showed a chromium center in a distorted octahedral coordination sphere. In the crystal, the packing was directed by O[sbnd]H⋯(O,Cl) hydrogen bonds and weak C[sbnd]H⋯O interactions to build a monoclinic P2₁/c supramolecular structure. The complex showed excellent properties as an initiator for the ring opening polymerization of є-caprolactone (CL) under solvent-free conditions. The obtained polymer showed high crystallinity (89.9%) and a decomposition temperature above 475 °C. In addition, the new complex was evaluated against epimastigotes from Trypanosoma cruzi (T. cruzi) strains. The results indicated that this complex has a high activity against this parasite with a minimum inhibitory concentration 50 (MIC₅₀) of 1.08 μg/mL. Interestingly, this compound showed little effect on erythrocytes, indicating that it is not cytotoxic. These results provide interesting contributions to the design of metal complexes by using simple and accessible ligands with activity against T. cruzi and with potential applications in the polymerization of CL.