A new class of N-H excited-state intramolecular proton transfer (ESIPT) molecules bearing localized zwitterionic tautomers

作者：Stasyuk Anton J; Chen Yi Ting; Chen Chi Lin; Wu Pei Jhen; Chou Pi Tai

来源：Physical Chemistry Chemical Physics, 2016, 18(35): 24428-24436.

DOI：10.1039/c6cp05236c

A series of new amino (NH)-type intramolecular hydrogen- bonding (H-bonding) compounds have been strategically designed and synthesized. These molecules comprise a 2-(imidazo[1,2-a]pyridin-2-yl)aniline moiety, in which one of the amino hydrogens was replaced with substituents of different electronic properties. This, together with the versatile capability for modifying the parent moiety, makes feasible comprehensive spectroscopy and dynamics studies of excited-state intramolecular proton transfer (ESIPT) as a function of N-H acidity. Different from other (NH)-type ESIPT systems where the ESIPT rate and exergonicity increase with an increase in the N-H acidity and hence the H-bonding strength, the results reveal an irregular relationship among ESIPT dynamics, thermodynamics and H-bond strength. This discrepancy may be rationalized by the localized zwitterionic nature of 2-(imidazo[1,2-a]pyridin-2-yl)aniline in the proton-transfer tautomer form, which is different from the pi-delocalized tautomer form in other (NH)-type ESIPT systems.

• 出版日期2016