Sectional intramolecular charge transfer manipulating in a D-A-D' coumarin derivative for recessive rewritable paper

Abstract

External-stimuli-responsiverewritable paper has attracted significant attention for application in secure information. However,to encrypt information on paperswhichcan not be read out under visible light is still challenging. In this work, recessive rewritable paper for security information handling was realized via sectional intramolecular charge transfer (SICT) manipulating in a delicately designed coumarin derivative CMNT. By rational arranging a thiophenyl group and a diethylamino group as electron donors at the 3- and 7-position of coumarin skeleton, respectively, CMNT exhibited obvious fluorescence switching upon BF3 and trimethylamine stimuli. After impregnating a filter paper into CMNT solution with low concentration (1 × 10−6 M), no color change of the paper could be observed under visible light. Meanwhile, when writing and erasing the information on the paper by BF3 ink and trimethylamine eraser, respectively, the process can only be witnessed under UV light. Studies revealed the ICT effect from diethylamino group to chromen-2-one was suppressed after adding BF3, while the ICT channel from thiophenyl group to chromen-2-one was retained, thus producing such unique phenomenon.