SYNTHESIS, CHARACTERIZATION AND BIOLOGICAL STUDIES OF SOME HYDRAZONES AND THEIR METAL COMPLEXES

Abstract

Several 5-arylfuran-2-carbaldehydes were prepared from furfural by a Meerwein arylation. These were then reacted with a few arylhydrazides to provide respective arylhydrazones which acted as the starting ligands. On reaction with copper, nickel and cobalt (d block elements) salts provided corresponding metal complexes. (Scheme). NH2 R + O CHO R O CHO O CH R N NH O C R' H2N NH C O R' (Hydrazide) M= Cu(II), Ni(II), Co(II) O C N H N C R' O M O C N H N C R' O R R M O C N H N C R' O R Cl (A) (B) O N C H N C O M O (C) R (Hydrazone) (5-arylfuran-2-carbaldehydes ) Both the conventional heating and microwave irradiation were employed for the formation of the hydrazides, hydrazones and the metal complexes. Microwave methods were time and yield efficient and presented as eco-friendly, neater and higher yields processes as viii compared to the conventional methods. All the new compounds were characterized through their elemental analyses and spectra (FTIR, 1H NMR, 13C NMR and EIMS). The metal complexes were further analyzed for their metal contents (ICP-OES) and chloride ions (Metrohm potentiometric autotitrator). Mass spectral fragmentation of the hydrazone ligands was also suggested. Further studies showed that the complexes formed in the ligand to metal ratios were 2:1 and 1:1 which helped identify them as Octahedron (A), Tetrahedron (B) and Square planar (C) in their geometry. Chloride ions when present are perhaps in the bridging position in the complexes. Biological screening of the ligands as well as their complexes was carried out to test for their antibacterial (three Gram Positive (Staphylococcus aureus, Bacillus subtilis and Actinobaculumschaalii) and six Gram Negative (Pseudomonas aerugenosa, Escherichia coli, Salmonella typhimurium, Bordetellabronchiseptica, Shigella and Salmonella) bacterial strains were tested) and antioxidant activity (three: in vitro methods used DPPH method, NO method and Phosphomolybdenum method). These products did not show any pronounced activities however.