Synthesis, characterization, thermal properties and biological activity of diazine-ring containing hydrazones and their metal complexes

New coordination compounds have been synthesized by reacting Zn(II) and Co(II) nitrate or acetate in the presence of triethylamine with Schiff-base ligands containing diazine-ring, pyridine-2-carbaldehyde phthalazine-1-hydrazone, HzPYH, and di(2-pyridyl)ketone 3-chloro-pyridazine-6-hydrazone, HpDPKH. Complexes of [Co(HzPY)2]·3.4H2O, [Zn(HzPY)2] and [Co(HpDPK)2]NO3·H2O were obtained. The crystal and the molecular structure of [Co(HzPY)2]·3.4H2O were determined using X-ray diffraction structure analysis. The compounds were characterized by elemental analysis, FT-IR and UV–Vis spectral data, conductivity and magnetic measurements, too. Except for the diamagnetic Co(III) compound with a nitrate counter-ion, [Co(HpDPK)2]NO3·H2O, all the complexes are neutral-type. The magnetic moment of [Co(HzPY)2]·3.4H2O indicated a low-spin octahedral complex which is relatively rear amongst octahedral Co(II) complexes. Hence, its magnetic moment was measured in the temperature range of 3–300 K. To obtain products in the form of single crystals and/or to increase the yield, the reactions were carried out in solutions with different solvents or recrystallized from solvent mixtures. To determine the nature of the solvent (if any) in the crystalline products and to gain better insight into the decomposition mechanism, coupled TG–MS measurements were carried out. The desolvated compounds were stable at relatively high temperatures (> 200 °C). The cytotoxic, antiproliferative and efflux pump inhibitory effects of the compounds were tested in multidrug-resistant mouse T-lymphoma cells to study their effect on the suppression of MDR. The antibacterial activity of the compounds was also tested. The results of the antibacterial tests were analysed to understand better the effect of the central atoms and the structure on a specific activity.