Abstract
Reaction between [RuCl
(CO)
]
and 1
-benzimidazol-2-ylmethyl-(
-phenyl)amine ligands (L
) functionalized with various electron-donating and electron-withdrawing substituents on the phenyl ring (R = H, 4-CH
, 4-Cl, 4-COOCH
, and 3-COOCH
) afforded the dark-stable photoactivatable carbon monoxide prodrugs of the general formula [RuCl
(CO)
L
]. Release of the CO molecules from the Ru(II) compounds was examined by monitoring the electronic and IR spectra upon illumination at 365 nm. A noticeable decrease in the intensities of the two characteristic
(CO) modes for Ru(CO)II2 species, and the growth of two new bands for the mono-carbonyl species and free CO, were the main features of the photolysis profiles. The cytotoxicity of the complexes towards breast cancer (MCF-7) cells was assessed with and without illumination at 365 nm. All the complexes except that with a 4-COOCH
group (IC
= 45.08 ± 3.5 μM) are nontoxic under dark conditions. Upon illumination, all the compounds acquired cytotoxicity in the following order: H > 4-COOCH
> 4-CH
> 4-Cl > 3-COOCH
. Investigation of the cytotoxicity of the CO-depleted fragments showed that the light-induced cytotoxicity can be attributed to the liberated CO and CO-depleted metal fragments, including the liberated benzimidazole ligands.