Abstract
An in cellulo study of the ultrafast excited state processes in the paradigm molecular light switch [Ru(bpy)2dppz](2+) by localized pump-probe spectroscopy is reported for the first time. The localization of [Ru(bpy)2dppz](2+) in HepG2 cells is verified by emission microscopy and the characteristic photoinduced picosecond dynamics of the molecular light switch is observed in cellulo. The observation of the typical phosphorescence stemming from a (3)MLCT state suggests that the [Ru(bpy)2dppz](2+) complex intercalates with the DNA in the nucleus. The results presented for this benchmark coordination compound reveal the necessity to study the photoinduced processes in coordination compounds for intracellular use, e.g. as sensors or as photodrugs, in the actual biological target environment in order to derive a detailed molecular mechanistic understanding of the excited-state properties of the systems in the actual biological target environment.