Synthesis, characterization and cancer cell growth inhibition activity of ruthenium(II) complexes bearing bidentate pyrrole-imine ligands

A series of bidentate pyrrole-imine ligands, [C₄H₃NH-(2-CH=N-R)] (1, R = cyclohexenyl; 2, R = CH₂CH₂-1-cyclohexenyl; 3, R = ^tBu; 4, R = CH₂-2-furyl; 5, R = 2-methoxylphenyl; 6, R = phenyl; 7, R = 3-nitrophenyl; 8, R = 2,6-di-isopropylphenyl; 9, R = 2,4,6-trimethylphenyl), were synthesized and their corresponding ruthenium metal compounds {Ru (ɳ⁶-p-cymene)[C₄H₃N-(2-CH=N-R)]Cl} (Ru-1∼Ru-9) were also synthesized. These ligands and ruthenium compounds were all characterized by ¹H and ¹³C NMR spectroscopy and some of their structures are also determined by single crystal X-ray crystallography. The Ru-1∼Ru-9 showed excellent GI₅₀ for PC-3 and DU-145 with the range of 3.83–12.13 and 4.25–11.22 μM, respectively. Among of these ruthenium compounds, Ru-6 has the best activity indicating phenyl ring is the key group on the imine substituents of these ruthenium compounds.