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

<p>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(MP_zOA)(NO₃)]₂ (<b>1</b>) and [Cu(3,7,11,15-tetramethylporphyrin)(H₂O)](NO₃)₂ (<b>2</b>), reported together with a Ni(II) complex, [Ni(MPzOA)₂(H₂O)₂]Br₂ (<b>3</b>). The compounds are characterized by single crystal X-ray structure analyses along with several physico-chemical and spectral parameters. Complex <b>1</b> is authenticated as a bis(μ-pyrazolato)dicopper(II), while <b>2</b> is a porphyrinogen and <b>3</b> is a distorted octahedral complex. Structural analyses of the complexes reveal that <b>1</b> crystallized in monoclinic <i>P2</i>_<i>1</i><i>/n</i> space group while <b>2</b> and <b>3</b> crystallized in monoclinic <i>C2/c</i> 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 <b>1</b> and <b>2</b> induce extensive DNA cleavage in the presence of H₂O₂ as an additive, whereas there is no change in degradation of super-coiled DNA by <b>3</b> in the presence of additive. The antimicrobial studies of the complexes against <i>Escherichia coli</i> DH5α bacteria strain indicated that all the complexes were capable of killing <i>E. coli</i> with different LD50 values.