Cu(II), Mn(II) and Zn(II) complexes of hydrazones with quaternary ammonium moiety: synthesis, experimental and theoretical characterization and cytotoxic activity

In this paper Cu(II), Mn(II) and Zn(II) complexes with N,N,N-trimethyl-2-oxo-2-(2-(1-(thiazol-2-yl)ethylidene)hydrazinyl)ethan-1-aminium chloride (HL1Cl) were synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis and DFT calculations. In all three complexes ligand (L1) is coordinated in deprotonated formally neutral zwitter-ionic form via NNO donor set atoms. Cu(II) and Zn (II) form mononuclear penta-coordinated complexes [CuL1(N3)(CH3OH)]BF4 and [ZnL1(N3)2], respectively, while with Mn(II) a binuclear [Mn2L12(μ-1,1-N3)2(N3)2]‧2CH3OH complex, with unusual distorted trigonal-prismatic geometry around metal centers, has been obtained. Antimicrobial activity was tested against a panel of Gram-negative and Gram-positive bacteria, two yeasts and one fungal strain. The binuclear Mn(II) complex showed antifungal activity of similar intensity as amphotericin B. Based on the results of the brine shrimp test and DPPH radical scavenging activity, the most active, Cu(II) and Mn(II) complexes, were selected for evaluation of cytotoxic activity against five malignant cancer cell lines (HeLa, A375, MCF7, PC-3 and A549) and one normal cell line HaCaT. Both complexes showed a significant activity. It should be pointed out that the activity of Mn(II) complex against breast cancer MCF7 cell is only slightly weaker than that of cisplatin, but with selectivity to the tumor cell line in comparison to normal HaCaT cells, which is non-existent in case of cisplatin.