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 [Ru2(p-cymene)2(μ-η4-C2O4)­Cl2] (2) and [Ru2(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.