For the assessment of the biological activity, the compounds were prepared as stock solutions in dimethylsulfoxide (DMSO). Similar to former reports , the 1 H NMR spectra of the functionalized diruthenium complexes 6, 7, 20, 22, 25 and 26 in DMSO-d6, recorded at 25°C 5 min and more than 1 month after sample preparation showed no significant modifications (see Figure in the Supporting Information), demonstrating a very good stability of the compounds in this highly complexing solvent.