Microwave-assisted synthesis of arene ruthenium(ii) complexes [(η6-RC6H5)Ru(m-MOPIP)Cl]Cl (R = -H and -CH3) as groove binder to c-myc G4 DNA

Abstract

Two arene Ru(II) complexes coordinated by 2-(3-methoxyphenyl)imidazole[4,5-f][1,10]phenanthroline, [(η⁶-RC₆H₅)Ru(m-MOPIP)Cl]Cl (R = H, 1; R = CH₃, 2), have been prepared under microwave irradiation; the crystal structure of 2 exhibits a typical “piano stool” conformation, with bond angles for N1–Ru1–Cl1 86.02 (14)° and N2–Ru1–Cl1 84.51 (14)°. The Ru–C distance for the Ru atom bound to the benzene ring is about 0.2178(8) nm, and the average Ru–N distance for Ru atom to the two chelating N atoms is about 0.2092(4) nm. The evaluation of in vitro anticancer activities revealed that these synthetic Ru(II) complexes selectively inhibited the growth of HepG2 hepatocellular carcinoma cells, with low cytotoxicity toward LO2 human normal liver cells. The results demonstrated that the complexes exhibited great selectivity between human cancer and normal cells by comparing with the ligand m-MOPIP. Furthermore, complexes 1 and 2 could bind to c-myc G4 DNA in groove binding mode in promising affinity, and the insertion of the methyl groups in the arene ligand contributed to strengthen the binding affinity. This was also confirmed by molecular docking calculation and ¹H NMR analysis which showed that both 1 and 2 can bind in the loop constructed by A6–G9 and G21–A25 base pairs in c-myc G4 DNA to block the replication of c-myc oligomer. Taken together, these results suggest that arene Ru(II) complexes display application potential as small molecule inhibitors of c-myc G4 DNA.