New fluorescent monomers and polymers displaying an intramolecular proton-transfer mechanism in the electronically excited state (ESIPT)

Eight new highly fluorescent benzazolylvinylene monomers were synthesized by reaction of 2-(4′-amino-2′-hydroxyphenyl)benzazoles with two functionalized vinylene derivatives and acryloyl chloride. The monomers were characterized by means of infrared, 13C and 1H-NMR and elemental analysis. UV-vis and steady-state fluorescence in solution were also applied in order to characterize its photophysical behaviour. The benzoxazole and benzimidazole derivatives are fluorescent in the blue-purple region and the benzothiazole in the green region. The monomers presented a Stokes shift between 51 and 159 nm. A dual fluorescence ascribed to a conformational equilibrium in solution in the ground state dependent on the solvent polarity could be observed in the monomers. The radical polymerization of the monomers with methyl(methacrylate) allowed the production of eight new fluorescent polymers with good optical and thermal properties.