Synthesis and characterization of some new complexes of Cu(II), Ni(II) and V(IV) with Schiff base derived from indole-3-carboxaldehyde. Biological activity on prokaryotes and eukaryotes

Six new Cu(II), Ni(II), and VO(II) complexes (1–6) with Schiff base 1-phenyl-2,3-dimethyl-4-(1H-indole-3-carboxaldehyde)-3-pyrazolin-5-one (HL) were synthesized. The Schiff base was prepared through the condensation of 1-phenyl-2,3-dimethyl-4-amino-3-pyrazolin-5-one (antipyrine) with 1H-indole-3-carboxaldehyde. The new obtained compounds were characterized by 1H NMR, 13C NMR, UV–VIS, IR, EPR spectroscopy, elemental analysis, molar electric conductibility, magnetic susceptibility and thermal gravimetric analysis. In addition, the structure of the ligand HL has been determined by X-ray diffraction methods. The biological activity of complex compounds was investigated in terms of antibacterial effect on prokaryotic cells, by using paper disc diffusion technique, and for antiproliferative effect on eukaryotic cells, by monitoring mitotic activity in timelapse videomicroscopy experiments. The compounds were screened for their antibacterial activity against gram-positive bacteria (Staphylococcus aureus var. Oxford 6538, Klebsielle pneumoniae ATCC 100131 and Legionella monocytogenes ATCC 35182), gram-negative bacteria (Escherichia coli ATCC 10536, Pseudomonas aeruginosa ATCC 9027 and Salmonella typhimurium ATCC 14028) and anti-fungal activity (Candida albicans and Aspergillus flavus) using paper disc diffusion technique. The minimum inhibitory concentrations (MICs) of the compounds were also determined by agar streak dilution method. Compounds 3 and 4 proved to be the most effective as antibacterial agents. The antiproliferative activity was investigated by counting the number of mitoses for HeLa, and MCF7 cells. No significant antiproliferative effect was noted for HL and complex 2, for both used cell types. For complexes 1 and 3 complete inhibition of cell proliferation was observed in the case of HeLa cells, while the effects on MCF7 cell proliferation were lower.In conclusion, six new complex compounds were synthesized, and their biological activity investigated on both prokaryotic and eukaryotic cells, proving that some of them could be putative therapeutic substances.

Synthesis, characterization, and biological activity investigation on prokaryotes and eukaryotes of novel Cu(II), Ni(II) and VO(II) complexes bearing indole-3-carboxaldehyde-based Schiff base as ligand. Six new Cu(II), Ni(II) and VO(II) complexes (1–6) with the Schiff base (HL) obtained through the condensation of 1-phenyl-2,3-dimethyl-4-amino-3-pyrazolin-5-one (antipyrine) with 1H-indole-3-carboxaldehyde were synthesized. The antiproliferative activity was investigated by counting the number of mitoses for HeLa and MCF7 cells in timelapse videomicroscopy experiments. No effect was noted for HL and complex 2, but complete inhibition of cell proliferation was observed for complexes 1 and 3.Figure optionsDownload as PowerPoint slideHighlights
► Six new Cu(II), Ni(II), and VO(II) complexes with Schiff base 1-phenyl-2,3-dimethyl-4-(1H-indole-3-carboxaldehyde)-3-pyrazolin-5-one were synthesized.
► The molecule HL is essentially planar except the phenyl ring of antipyrine moiety which is rotated at 65° to the adjacent five-membered ring.
► The EPR parameters g//, g⊥, A// and the energies of d–d transition were used to evaluate the bonding parameters α2, β2, δ2.
►  Antimicrobial study reveals that metal complexes have more biological activity than free ligand.