Exploration of ESIPT in 4,6-O-Ethylidene-N-(2-hydroxybenzylidene)-β-D-glucopyranosylamine and Its Application in Selective Turn-on Response Toward Lu(III) ion.

4,6-O-Ethylidene-N-(2-hydroxybenzylidene)-β-D-glucopyranosylamine (PL1) exhibits excited state intramolecular proton transfer (ESIPT) mechanism, which has been established by experimental and theoretical calculations. Further, PL1 selectively interacts with Lu3+ ion yielding a turn-on response in methanol, where the emission intensity of the former enhances (~15 fold) after metal ion interaction. The complexation has been investigated using various analytical tools like UV-visible absorption/emission, nuclear magnetic resonance spectroscopy and lifetime studies. The relative quantum yield of PL1 (0.0043) enhances to 0.1025 upon interaction with the Lu3+ ion. The studies on stoichiometry by Job's plot, ESI mass spectrometry and density functional theory calculations revealed the ligand-to-metal interaction in 2 : 1 ratio.