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Solvent dependent excited state spectral properties of 4-hydroxyacridine: Evidence for only water mediated excited state proton transfer process

Paper ID Volume ID Publish Year Pages File Format Full-Text
29005 44112 2008 9 PDF Available
Title
Solvent dependent excited state spectral properties of 4-hydroxyacridine: Evidence for only water mediated excited state proton transfer process
Abstract

The possibility of ground and excited state proton transfer reaction across the five member intramolecular hydrogen bonded ring in 4-hydroxyacridine (4-HA) has been investigated spectroscopically and the experimental results have been correlated with quantum chemical calculations. The difference in the emissive behaviour of 4-HA in different types of solvents is due to the presence of different species in the excited state. In non-polar solvents, the species present is non-fluorescing in nature, whereas 4-HA molecule shows normal emission from intramolecularly hydrogen bonded closed conformer in polar aprotic solvents. In polar protic solvents like MeOH, EtOH, etc. (except water), a single broad emission band is attributed to the hydrogen bonded solvated form of 4-HA. However, in case of water, fluorescence from the tautomeric form of 4-HA is observed apart from emission from the solvated form. Emission from the tautomeric form may arise due to double proton transfer via a single water molecule bonded to 4-HA. Evaluation of the potential energy surfaces by quantum chemical calculations using density functional theory (DFT) and time dependent density functional theory (TDDFT), however, points towards the possibility of proton transfer—both intrinsic intramolecular as well as water mediated in the first excited state of 4-HA.

Keywords
4-Hydroxyacridine; Intermolecular proton transfer; Absorption; Fluorescence; Density Functional Theory (DFT)
First Page Preview
Solvent dependent excited state spectral properties of 4-hydroxyacridine: Evidence for only water mediated excited state proton transfer process
Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 200, Issues 2–3, 15 December 2008, Pages 325–333
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering