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Slow proton transfer dynamics of a four member intramolecular hydrogen bonded isoindole fused imidazole system: A spectroscopic approach to photophysical properties

Paper ID Volume ID Publish Year Pages File Format Full-Text
25860 43894 2015 9 PDF Available
Title
Slow proton transfer dynamics of a four member intramolecular hydrogen bonded isoindole fused imidazole system: A spectroscopic approach to photophysical properties
Abstract

•Photophysics of pharmaceutically important heterocyclic of isoindole fused imidazole system.•Excited state lactim–lactam tautomerism reaction studied spectroscopically.•Proton transfer in four member hydrogen bonded network favors over six member ring.•Irreversible and slow (kPT ∼ 109 s−1) proton transfer dynamics.

Spectral studies of 1-(2-hydroxy-5-chloro-phenyl)-3,5-dioxo-1H-imidazo-[3,4-b] isoindol (ADCL) in various solvents reveal the occurrence of excited state intramolecular proton transfer (ESIPT) process. Excitation at the shorter wavelengths preferentially leads to dual emission from an equilibrium mixture of excited state normal (N*, lactim form) and tautomeric (T*, lactam form) form due to the operation of proton transfer process. The proton transfer dynamics is found to be very slow in various organic solvents and it occurs in the nano-second time scale. This may be due to high energy barrier along the proton transfer coordinate through a strained four member hydrogen bonded network compared to the usual six member hydrogen bonded ring.

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Keywords
1-(2-Hydroxy-5-chloro-phenyl)-3,5-dioxo-1H-imidazo-[3,4-b] isoindol; Irreversible ESIPT; Dynamics; Emission spectroscopy
First Page Preview
Slow proton transfer dynamics of a four member intramolecular hydrogen bonded isoindole fused imidazole system: A spectroscopic approach to photophysical properties
Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 302, 1 April 2015, Pages 42–50
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering