A rhodamine 6G derived Schiff base as a fluorescent and colorimetric probe for pH detection and its crystal structure

A new rhodamine-based fluorescent H+ probe (RP1) which is highly selective and sensitive has been developed. At pH values of 1.1-3.1, the probe exhibits remarkable fluorescent changes which are due to the ring-opening property of the rhodamine spirolactam. The pKa value of RP1 was determined to be 2.08 (±0.07). Furthermore, at low pH values, RP1 exhibits a color change from colorless to pink making RP1 suitable for the naked-eye detection of H+. Finally, fourteen metal ions were tested for possible interferences and not were found.243