Photochemical and complexation studies for new fluorescent and colored chelator

Abstract

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 mM, 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 Ca^2C 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.

Key Words:

• Photoinduced intramolecular proton transfer
• Photoresponsive chelators
• Dissociation constant