Binuclear azide-bridged hydrazone Cu(II) complex: Synthesis, characterization and evaluation of biological activity

The condensation product of 7-acetyl-6-azaindole and Girard's T reagent ((E)-2-(2-(1-(1H-pyrrolo[2,3-c]pyridin-7-yl)ethylidene)hydrazineyl)- N,N,N-trimethyl-2-oxoethan-1-aminium, HL ligand) was used as a ligand in the reaction with Cu(BF4)2?6H2O and NaN3. The reaction led to the formation of a binuclear Cu(II) complex containing two end-to-end (di-m-1,3-N3) azide bridges, as well as two NNO-donor hydrazone ligands, forming an axially elongated square pyramidal geometry around each Cu(II) center. This end-to-end (di-m-1,3- N3) azide bridge binding mode has not yet occurred in Cu(II) complexes containing the NNO-donor hydrazone ligands, which makes the structure of the complex even more interesting for further studies. The complex was characterized by elemental analysis, IR spectroscopy and X-ray crystallography, and it was found that it crystallizes in the triclinic space group P-1 with the asymmetric unit comprising one Cu(II) centre, zwitterionic ligand L, one azide (N3?) ligand, and BF4? counter anion. Examination of antimicrobial activity of the complex shows higher antifungal and antibacterial activity towards tested Gram-positive bacteria in comparison to the hydrazone ligand, with the antifungal activity of the complex even being comparable to the activity of amphotericin B.