Syntheses and Acid-Stimulus Responsiveness of Aminobenzopyranoxanthene Spiroethers

Morpholine‐Substituted Rhodamine Analogue with Multi‐Configurational Switches for Optical Sensing of pH Gradient under Extreme Acidic Environments

“…As regards the acidic pH responsiveness of ABPX‐SL ( 1 ), compound 1 facilitated the opening of both spiro‐rings through the elimination of the carboxylic acids to give D ++ without the observation of M + (Figure 1 b, Figure S1). In our previous experiments, we showed that M + was formed under acidic pH conditions when SL in ABPX was replaced with spiroether (SE) (Figure 1 b and Figure S1) [15] . Although this approach is viable, compound 2 still suffers from low‐contrast color change due to small changes in the absorption spectral shift.…”

“…In our previous experiments,w es howedt hat M + + was formed under acidic pH conditions when SL in ABPX was replaced with spiroether (SE) (Figure 1b and Figure S1). [15] Althought his approach is viable, compound 2 still suffers from low-contrast color change due to small changes in the absorption spectral shift. Further systematic understanding of the structure-property relationship (SPR) for enhancing pH responsivenessi sw arranted to develop practical pH-responsive molecules and new applications.…”