Résumé : Under visible irradiation, [Ru(TAP)2(phen)]2+(Cl−)2, [Ru(TAP)2(POQ-Nmet)]2+(Cl−)2 and [Ru(bpy)2(phen)]2+(Cl−)2 were able to dramatically reduce the in vitro transcription of a plasmid DNA template by a bacteriophage RNA polymerase. This photoactivity is related to two different mechanisms of reactivity towards DNA exhibited by these complexes under illumination.