Synthesis and study of the sensory properties of bichromophoric systems based on 1,8-naphthalimide and styrylpyridine, containing an oligoglycolic receptor fragment

Naphthalimide—styrylpyridine-, styrylpyridine—styrylpyridine-, and naphthalimide—naphthalimide-type bichromophoric chemosensors for metal cations were obtained. Their photoactive fragments were linked by an open-chain oligoethylene glycol spacer, which acted as a receptor group. Optical and NMR spectroscopy was used to show that these compounds can form complexes with calcium and barium cations in an acetonitrile solution. In the case of an “asymmetric” bichromophore, the binding of these cations was accompanied by a redshift of the absorption and emission bands of styrylpyridine, a decrease of the efficiency of resonance energy transfer in the system, and an increase in the intensity of the fluorescence band of the naphthalimide residue. Complexation led to a hypsofluoric shift of the maximum in the fluorescence spectrum of the “symmetric” bis(styryl-pyridine). In both cases, spectral changes made it possible to register a ratiometric fluorescent response to the presence of metal cations in the solution.