AIEE-TICT quadrupolar push-pull quinoxaline derivatives displaying solvatochromism, acidofluorochromism and logic gate operation

Abstract

A series of novel quadrupolar push-pull molecules based on quinoxaline moiety as an electron acceptor, biphenyl as a spacer and methoxy groups as electron donors was designed, synthesized and characterized. Their structural, photophysical, thermal, aggregation and acidofluorochromic properties were investigated. Photophysical studies showed that the introduction of an electron withdrawing group onto the quinoxaline moiety caused red shifts in absorption and emission maxima due to enhanced ICT. A positive solvatochromic behavior with large bathochromic shifts, up to 106 nm, was observed in the emission wavelength upon increasing solvent polarity from toluene to DMSO. All compounds displayed TICT-AIEE characteristics in DMSO-Water. Single crystal X-ray diffraction studies of QM2, QM4-QM6 revealed highly twisted structures and the absence of π-π stacking interactions. A visual color change from colorless to yellow accompanied by fluorescence quenching was observed in the molecules upon treatment of DCM solution with TFA and the changes were reversed upon addition of TEA. Reversible acidofluorochromism was also observed in the solid state. Filter paper strips coated with QM1 and QM4 were fabricated for detecting TFA. An IMPLICATION molecular logic gate operation can be performed on these molecules using acid and base as chemical inputs.