Novel Y-shaped AIEE-TICT active π-extended quinoxalines-based donor–acceptor molecules displaying acidofluorochromism and temperature dependent emission

Seven novel donor–acceptor-donor type push–pull quadrupolar quinoxaline scaffolds exhibiting blue or green emission in solution were synthesised in good yields by Heck coupling reaction. The photophysical properties of these quinoxaline derivatives were tuned by introducing functional groups of varying electronic nature on the quinoxaline moiety. Mega Stokes shifts and large bathochromic shifts in emission wavelength were observed on moving from non-polar toluene to polar DMSO. A twisted structural conformation and donor–acceptor interactions along with herringbone arrangement were revealed by single crystal XRD studies. "on–off-on" fluorescence switching was observed upon increasing water fraction in DMSO-water mixture. A reversible switching in colour and emission properties upon treatment with TFA and TEA in both solution and solid state was also observed which was utilised for the fabrication of filter paper strips for the detection of volatile acids. These compounds also displayed linear dependence of emission maxima on temperature.