l-Tyrosine derived fluorescent molecular probes as solvent mediated flip-flop halide (iodide/fluoride) sensors and reversible chromogenic pH indicators

Abstract

In this work, we have developed two single-molecular probes, (S)-3-(4-hydroxyphenyl)-2-((4-nitrobenzyl)amino)propanoic acid (H₂Tyr-4-nitro, 1) and (S)-3-(4-hydroxyphenyl)-2-((3-nitrobenzyl)amino)propanoic acid (H₂Tyr-3-nitro, 2), from cheap and readily available L-tyrosine and demonstrated their use as (i) a solvent mediated differential fluorescent sensor for iodide in aqueous methanol and fluoride in aqueous DMSO and (ii) a reversible chromogenic pH indicator in DMSO. A flip-flop halide sensor also acting as a pH indicator is unprecedented.