Nitis Chandra Saha

Synthesis and characterization of two Cu(II) complexes with a new pyrazole-based Schiff base ligand: crystallography, DNA interaction and antimicrobial activity of Ni(II) and Cu(II) complexes

Abstract Reaction of Cu(II) nitrate with a new pyrazole-based Schiff base ligand, 5-methyl-3-formylpyrazole-N-(2′-methylphenoxy)methyleneimine (MPzOA), afforded two types of Cu(II) complexes at different reaction temperatures, [Cu(MPzOA)(NO3)]2 (1) and [Cu(3,7,11,15-tetramethylporphyrin)(H2O)](NO3)2 (2), reported together with a Ni(II) complex, [Ni(MPzOA)2(H2O)2]Br2 (3). The compounds are characterized by single crystal X-ray structure analyses along with several physico-chemical and spectral parameters. Complex 1 is authenticated as a bis(μ-pyrazolato)dicopper(II), while 2 is a porphyrinogen and 3 is a distorted octahedral complex. Structural analyses of the complexes reveal that 1 crystallized in monoclinic P21/n space group while 2 and 3 crystallized in monoclinic C2/c space group. DNA-binding studies of the complexes have shown that the complexes interact with CT-DNA. DNA-cleavage studies with plasmid DNA have shown that 1 and 2 induce extensive DNA cleavage in the presence of H2O2 as an additive, whereas there is no change in degradation of super-coiled DNA by 3 in the presence of additive. The antimicrobial studies of the complexes against Escherichia coli DH5α bacteria strain indicated that all the complexes were capable of killing E. coli with different LD50 values.

Synthesis, characterization, X-ray crystallography, and antimicrobial activities of Ni(II) and Cu(II) complexes with a salicylaldehyde-based thiosemicarbazone ligand

A new salicylaldehyde-based ‘ONS’ tridentate salicylaldehyde-N(4)-diethylthiosemicarbazone (H2SANEt2) has been synthesized and characterized by elemental analyses, mass, IR, and 1H NMR spectral parameters. The coordination mode of the synthesized ligand is reported by solid state isolation and physico-chemical identification of Ni(II) and Cu(II) complexes, [Ni(SANEt2)]2 (1) and [Cu(SANEt2)]2 (2). Both complexes are neutral and oxygen-bridged dinuclear species. The ligand is bideprotonated ‘ONS’ tridentate in both complexes. IR spectral data indicate that coordination of each metal of the two complexes occurs through phenolic oxygen, azomethine nitrogen, and thiolato sulfur. X-ray crystallographic data of 1 and 2 (both monoclinic, P21/c) show a MONSO (where M=Ni and Cu) square-planar coordination around each metal. Magnetic studies of 2 show that the two Cu(II) centers are strongly antiferromagnetically coupled via the bridging phenoxo O. All the synthesized compounds were tested for their in vitro antimicrobial activities against pathogenic bacteria. The inhibition power of the complexes was greater than the parent ligand.