Synthesis, characterization, crystal structure and antitumor activities of a novel demethylcantharidato bridged copper(II) phenanthroline complex

A new polymeric demethylcantharidato (DCA) bridged copper(II) phenanthroline (phen) complex ([Cu(DCA)(phen)] _n ·nH₂O) has been synthesized and characterized by elemental analysis, IR and electronic spectra studies, molar conductivity measurement, and single crystal X-ray diffraction. The complex crystallizes in the orthorhombic space group Pbca with crystallographic data: a = 12.4537(4) Å, b = 9.3897(5) Å, c = 30.1264(10) Å, and Z = 8. In the crystal structure, the octahedral coordinated copper(II) ions are bridged by demethylcantharidate ligands into a one-dimensional zigzag-like structure with the Cu…Cu separation of 6.1719 Å, along with phen ligands attached to both sides of the chain alternatively. Interdigitation of the chelating phen ligands of two neighboring chains via hydrophobic interaction and van der Waals forces along ac plane forms two-dimensional polymeric bilayers with discrete water sandwich layer between the adjacent polymeric bilayers. The evaluation of the cytotoxic activity of the copper(II) complex against HCT-8 (colorectal carcinoma), A549 (pulmonary carcinoma), HeLa (cervical cancer), HepG2 (hepatocarcinoma), BGC-823 (gastric carcinoma), and MCF-7 (breast adenocarcinoma) cell lines revealed that it is a potent cytotoxic agent, superior to Na₂DCA and phen against HeLa, HepG2 and BGC-823 cells.