Rational molecular design: functional quinoline derivatives for PA detection, gaseous acid/base switching and anion-controlled fluorescence

Three new D--A quinoline derivatives (G1, G2 and G3) were synthesized by facile methods. The three obtained ICT molecules revealed evident solvatochromic effect. Importantly, G1 and G2 can be effectively applied as powerful tools for PA detection in the monomer state with low limits of detection (LOD). The fluorescence quenching by PA can be attributed to the obstruction of ICT process in the quenching process. In solid-state, owing to reversible transformation by protonation and deprotonation, the three compounds exhibited excellent acid-base switching. Meanwhile, six compounds containing different anions (G(2a), G(2b), G(2c), G(2d), G(2e), G(2f)) based on G2 were obtained by anion regulation in methanol. Importantly, the findings demonstrated distinct differences in the solid-state fluorescence of these compounds. These differences may arise from controlling anions to form different molecular packing arrangements.