A ratiometric rhodamine-naphthalimide pH selective probe built on the basis of a PAMAM light-harvesting architecture

PAMAM light harvesting antenna of second generation was synthesized and investigated. Novel compound was configured as a wavelength-shifting bichromophoric molecule where the system surface is labeled with yellow-green emitting 4-(N,N-dimethylamino)ethylamino-1,8-naphthalimide “donor” units capable of absorbing light and efficiently transferring the energy to a focal Rhodamine 6G “acceptor”. Furthermore, the 1,8-naphthalimide periphery of the system was designed on the “fluorophore-spacer-receptor” format, capable of acting as a molecular fluorescence photoinduced electron transfer based probe. Due to the both effects, photoinduced electron transfer in the periphery of the system and pH dependent rhodamine core absorption, novel antenna is able to act as a selective ratiometric pH fluorescence probe in aqueous medium. Thus, the distinguishing features of light-harvesting systems (fluorescence resonance energy transfer) were successfully combined with the properties of classical ring-opening sensor systems, which may be beneficial for monitoring pH variations in complex samples.