Fluorescent indolo[2,3 -b ]quinoxalin-2-yl(phenyl)methanone dyes: photophysical, AIE activity, electrochemical, and theoretical studies

Herein, we have synthesized four indolo[2,3- b ]quinoxalin-2-yl)(phenyl)methanone derivatives by cyclocondensation. The photophysical studies of dyes in various solvents and neat solid film exhibit typical electronic spectra with inbuilt intramolecular charge transfer (ICT) ( λ max : 397–490 nm) confirming donor–acceptor architecture. Herein, dyes fluoresce in the blue-orange region ( λ Emax : 435–614) on excitation at their ICT maxima in toluene, ethyl acetate, chloroform, DMSO, and neat solid film. Two dyes, which exhibit good emission intensity in all mediums, were studied for aggregation-induced emission (AIE) effect. Electrochemical studies indicate the dyes possess relatively low lying LUMO (− 3.65 to − 3.98 eV) comparable to reported n-type/electron-transporting materials. The HOMO and LUMO energy levels were evaluated by DFT and TD-DFT calculations. TGA analysis shows the dyes exhibit good thermal stability. The characteristic optoelectronic properties and thermal stability signify these dyes are potential candidates for their application in optoelectronics. Graphical abstract