Anticancer properties, apoptosis and catecholase mimic activities of dinuclear cobalt(II) and copper(II) Schiff base complexes.

The present work describes coordination chemistry and biological evaluation of two novel dinuclear complexes [Co₂(HL¹)₂(H₂O)₂]·8H₂O (1) and [Cu₂(L²)₂] (2) obtained from the Schiff base ligands, H₃L¹ and H₂L² (formed in situ). The two complexes are characterized by single crystal X-ray, spectral and variable temperature magnetic and theoretical (DFT/TDDFT) analysis. X-ray analysis confirms both the complexes to be dinuclear with distorted octahedral and square pyramidal geometry around Co(II) and Cu(II) ions, respectively. Magnetic studies reveal presence of moderate ferromagnetic interactions in both the complexes with J = 98 (1) and 32 (2) cm^-1. The magnetic interactions are further corroborated by DFT studies. Co(II) complex (1) exhibited enhanced catecholase activity with K_cat = 213.48 h^-1, which is attributed to the greater extent of charge contribution on Co²⁺ as compared to Cu²⁺ as determined by DFT calculations. Furthermore, both the complexes show potent anticancer activity toward HeLa (cervical) and A549 (lung) cancer cell lines with IC₅₀ = 6-7 µM at 48 h, which ascertains both the complexes as better anticancer drugs than cisplatin. Furthermore, 1 and 2 exhibit apoptosis of HeLa cells by demonstrating nuclear blebbings with shrinking morphology. Hence, the present complexes could be employed as a model for metalloenzymes as well as potential anticancer substituents of cisplatin in future course.