Coordination-Driven Self-Assembly and Anticancer Potency Studies of Arene-Ruthenium-Based Molecular Metalla-Rectangles

The two new large molecular metalla-rectangles 6 and 8 were obtained by the reaction of the two different arene-ruthenium acceptors [Ru-2(p-cymene)(2)(mu-eta(4)-C2O4)Cl-2] (2) and [Ru-2(p-cymene)(2)(donq)(Cl)(2)] (donq = 5,8-dioxido-1,4-naphthoquinonato) (4) with a symmetrical N,N'-bis(4-(pyridin-4-ylethynyl)phenyl)-terephthalamide (1) donor ligand. Both metalla-rectangles were isolated in good yields as triflate salts and were characterized by multinuclear NMR, ESI-MS, and UV-vis spectroscopy. X-ray crystallography of 6 confirmed a molecular metalla-rectangle. The cytotoxicities of metalla-rectangles 6-9 were established in SK-hep-1 (liver cancer), AGS (gastric cancer), and HCT-15 (colorectal cancer) human cancer cell lines. The cytotoxicity of metalla-rectangle 8 was found to be considerably stronger against all cancer cell lines, even much more effective than the well-known anticancer drugs doxorubicin and cisplatin. In addition, expressions of APC and p53, colorectal cancer suppressor genes, were significantly increased following exposure to the metalla-rectangle 8.