Two new photochromic supramolecular compositions based on viologen: photocontrolled fluorescence, aniline detection and inkless erasable printing performance

Abstract

Two supramolecular components {[3-BCBPY][H₃BTEC]₂}_n (1) and {[H₂BPYBC]_1/2[H₃BTEC]·H₂O}_n (2) based on benzene carboxylic acid (H₄BTEC = 1,2,4,5-benzenetetracarboxylic acid) and different viologen cations (3-BCBPY·2Cl = 1,1′-bis(3-cyanobenzyl)-4,4′-bipyridinium chloride, and 4-BCBPY·2Cl = 1,1′-bis(4-cyanobenzyl)-4,4′-bipyridinium chloride) were synthesized. Single crystal X-ray diffraction analysis showed that the three-dimensional supramolecular network was constructed in compounds 1 and 2, due to the hydrogen bond between H₃BTEC⁻ and 3-BCBPY²⁺ and the hydrogen bond between H₃BTEC⁻, H₂BPYBC²⁺ and water molecules, respectively. Both compounds 1 and 2 exhibit photochromic behavior of electron transfer. However, the discoloration speed of compound 2 is slower than that of compound 1, which may be due to the higher ionic state of compound 1 increasing the potential. At the same time, the two compounds also showed interesting photomodulated fluorescence behavior. Time-dependent density functional theory (TDDFT) was used to study the discoloration mechanism of compounds 1 and 2. Compound 1 exhibits selective sensing of aniline and triethylamine when exposed to different organic amines. And through the phenomenon of visual discoloration and fluorescence quenching, the sensing of aniline by compound 1 was confirmed, and the minimum concentration of detection was 10⁻⁵ M. It is also possible to completely dissolve compound 1 in ammonia water or coat and deposit compound 1 on paper with an absolute ethanol solution. These two types of paper can be used as inkless and erasable printing media and can be printed repeatedly at least five times.