A highly selective ratiometric fluorescent pH probe based on a PAMAM wavelength-shifting bichromophoric system

• PAMAM antenna decorated with Rhodamine 6G and 1,8-naphthalimides is synthesized.
• Periphery of the antenna is designed as a PET based fluorescence probe.
• System manifests excellent selective response to protons in aqueous medium.
• Core emission of the systems is enhanced 30 times as a function of pH.
• Bichromophoric system acts as a selective ratiometric probe in complex samples.

A novel PAMAM wavelength-shifting bichromophoric system has been successfully developed. Novel compound was configured as a light harvesting antenna 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”. The 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 the fluorescence resonance energy transfer systems were successfully combined with the properties of classical ring-opening charge transfer systems, which may be beneficially for monitoring pH variations in complex samples.

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