Trans-C versus Cis-C thermally induced isomerisation of a terpyridine adduct of cytotoxic cycloruthenated compound.

Two novel cycloruthenated compounds, 2 and 3 , derived from cycloruthenated 2-phenyl pyridine (Ru(PhPy)) have been synthesized by adding one equivalent of 2,2′;6′,2″-terpyridine (terpy) to [Ru(2-C 6 H 4 -2′-C 5 H 4 N-κC,N)(MeCN) 4 ]PF 6 in MeOH/MeCN (16:1) at reflux temperature as a mixture of 1:1 isomers. The structures of both compounds that were formed under kinetic and thermodynamic control respectively, differ by the position of the central pyridine unit of terpy that was found trans or cis to the C-Ru bond of the Ru(PhPy) unit for 2 and 3 respectively. Whereas 2 did not afford substitution reactions when treated with any ligand, the substitution by MeOH or H 2 O of the MeCN trans to C in 3 could be followed by UV-vis spectroscopy. Moreover, the reaction in MeOH between 3 and imidazoles afforded new cycloruthenated compounds, 6a and 6b whose cytotoxicities, together with that of 2 and 3 , against HCT116 and AGS cancer cells were determined. [ABSTRACT FROM AUTHOR]