Synthesis and characterization of new green and orange region emitting anthracene based oxazol-5-one dyes

Abstract

New anthracene oxazol-5-one dyes featuring an extended π-conjugated electron system have been successfully prepared by Erlenmeyer synthesis, structurally characterized and their spectroscopic properties were investigated by UV–vis absorption spectroscopy and fluorescence spectroscopy. The oxazol-5-ones were attached to the 9-position of the anthracene to obtain the desired structures. The dyes are having extended conjugation throughout their structure with oxazol-5-one ring as the chromophore. The spectral properties of the oxazol-5-one ring were monitored with respect to the substituents at the phenyl ring. All of the dyes synthesized show good solubility in common organic solvents. Also in order to establish whether there was any solvent affects the absorption and emission spectra of the compounds were measured in the solvents of acetonitrile, tetrahydrofuran and chloroform which have different polarity. Moreover, their absorption and emission properties were investigated in plasticized PVC film matrix. In comparison to the solution phase, the dyes displayed enhanced fluorescence emission quantum yield values when embedded in poly(vinyl chloride) polymer film. The anthracene based oxazol-5-ones were found to emit in the green portion of the spectrum for 2a and 2b, and in the orange portion of the spectrum for 2c. By attachment of nitro substituent at the para position of the phenyl ring bound to oxazol-5-one core, the fluorescence maxima could be effectively modulated from the green region of the spectra to the orange region. 4-(9-anthralydene)-2-(4-nitrophenyl)oxazol-5-one (2c) exhibits large Stokes shift up to 146 nm presumably due to intramolecular charge transfer.