Photochemical and complexation studies for new fluorescent and colored chelator

The photo-induced intramolecular proton (or hydrogen atom) transfer (ESIPT) and metal binding properties of Oxa-ester were studied in methanol solution. The dissociation constant between Oxa-ester and the metal ion was highly dependent with the metal ion and was determined by Hill plots or iterative least squares fitting to be 447 mM, 14.9 μM, and 290 nM for Ca2+, Zn2+, and Cu2+, respectively, in methanol. The fluorescence intensity of Oxa-ester greatly increased with increasing concentration of Zn2+, while the fluorescence intensity decreased with the addition of Ca2+ and Cu2+. Transient absorption spectroscopy revealed that Oxa-ester underwent ESIPT to give Z-NH isomer in the excited state in benzene, while Oxa did not undergo ESIPT probably due to the hydrogen bonding with solvent water.