Unusual mode of protein binding by a cytotoxic π-arene ruthenium() piano-stool compound containing an O,S-chelating ligand

A new pseudo-octahedral π-arene ruthenium( ii ) piano-stool compound, containing an O,S-bidentate ligand (compound 1 ) and showing significant cytotoxic activity in vitro , was synthesized and characterized. In solution stability and interaction with the model protein bovine pancreatic ribonuclease (RNase A) were investigated by using UV-Vis absorption spectroscopy. Its crystal structure and that of the adduct formed upon reaction with RNase A were obtained by X-ray crystallography. The comparison between the structure of purified compound 1 and that of the fragment bound to RNase A reveals an unusual mode of protein binding that includes ligand exchange and alteration of coordination sphere geometry. A new π-arene Ru( ii ) piano-stool compound, showing significant cytotoxic activity in vitro , was synthesized. The X-ray structure of this compound and that of its complex with RNase A were determined.