Synthesis, crystal structure, DNA binding and antitumor studies of ß-diketonate complexes of divalent copper, zinc and palladium

This paper reports a simple approach for the synthesis of three pairs of novel mononuclear β-diketonate complexes of copper(II), zinc(II) and palladium(II) from monobasic O^O donor ligands 3-phenyl-4-fluorobenzolyl-5-isoxazolone (HL1) and 3-phenyl-4-toluyl-5-isxoazolone (HL2). The synthesized compounds are characterized by FT-IR, ESI/FAB mass, 1H NMR, UV–visible and thermogravimetric analyses. The free ligand HL1 and the copper(II) complex, [Cu(L2)2(CH3OH)2] are unambiguously characterized by single crystal X-ray diffraction studies. The free ligand HL1 has adopted orthorhombic crystal system with P2(1) space group and the unit cell parameters are a = 8.1552(3), b = 10.1169(4), c = 17.0819(6) Å, and α = β = γ = 90°. The crystal structure of the complex, [Cu(L2)2(CH3OH)2] is monoclinic with P2(1)/c space group and the unit cell parameters are a = 10.2571(2), b = 16.2640(3), c = 20.1717(3) Å, and α = 90, β = 99.56 and γ = 90°. The copper(II) complex has adopted distorted octahedral geometry where the z-axis is occupied by two solvent methanol molecules according to the crystal data. While the EPR spectra of both the Cu(II) complexes display a strong axial signal with g|| ≈ 2.2 and g⊥ ≈ 2.0, which obviously suggests the square planar geometry around the copper(II) ion. The interaction of the complexes with calf thymus DNA (CT-DNA) was investigated using UV–visible and fluorescence spectroscopic techniques. Anticancer activity of the complexes revealed their potential towards inhibiting the growth of human breast cancer cell lines, MDA-MB-231. The palladium complexes of both the ligands are found to be good in exhibiting apoptosis. Moreover, the complexes of fluoro-substituted ligand are better antimicrobial agents when compared with those of methyl substituted ligand.