Design, synthesis and pH sensing properties of novel 1,8-naphtalimide-based bichromophoric system

In this work we report on the design, synthesis and sensor properties of a novel bichromophoric sensor system based on 1,8-naphthalimide fluorophores. The synthesized dyad was configured as a fluorescent wavelength-shifting energy transfer chromophore. The novel donor-acceptor system contains blue emitting 4-methoxy-1,8-naphthalimide donor dye, capable of both absorbing light and efficiently transferring the energy to yellow-green emitting 4-N-methylpiperazinyl-1,8-naphthalimide acceptor. The energy-transfer efficiency in the dyad system was calculated to be more than 99%. The acceptor unit in the donor-acceptor system was also designed as a PET based sensor according to the "fluorophore-spacer-receptor" model. The fluorescence behaviour of the bichromophoric system was investigated as a function of pH. The fluorescence enhancement of the novel dyad in acidic media was more than 29 times indicating the high ability of the system to act as an efficient pH chemosensor.