Three new Cu(II) and Cd(II) complexes with 3-(2-pyridyl)pyrazole-based ligand: Syntheses, crystal structures, and evaluations for bioactivities

Three new complexes [Cu(L)2(NO3)](NO3)(H2O)1/2(CH3OH)1/2 (1), [Cd(L)2(NO3)2](H2O)3 (2) and [Cd(L)2(ClO4)(CH3OH)](ClO4)(H2O)1/4(CH3OH) (3) (L = 1-[3-(2-pyridyl)pyrazol-1-ylmethyl]naphthalene) were synthesized and characterized by elemental analyses, IR and X-ray diffraction analysis. Among them, the Cu(II) and Cd(II) ions were both coordinated by four N donors from two distinct L ligands via N,N-bidentate chelating coordination mode. Additional weak interactions, such as the face-to-face π–π stacking and C–H⋯O H-bonding interactions, linked the mononuclear unit into 1D chain and further into 2D network. Complexes 1–3 were subjected to biological assays in vitro against six different cancer cell lines. All of them exhibited cytotoxic specificity and notable cancer cell inhibitory rate. The interactions of 1–3 with calf thymus DNA were investigated by thermal denaturation, viscosity measurements, spectrophotometric and electrophoresis methods. The results indicate that these complexes bound to DNA by intercalation mode via the ligand L and had different nuclease activities, which were in good agreement with their DNA-binding strength. Moreover, the central metal ions of 1–3 played a vital role in DNA-binding behaviors, DNA-cleavage activities and cytotoxicities, whereas the contribution of the different counter anions to their bioactivities also should not be ignored.