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E-Journal of Chemistry
Volume 4, Issue 4, Pages 523-530

Photophysical Study of 1,5 – Diaminoanthraquinone in Different Solvents and at Various pH

P. Sivakumar, S. Kothai Nayaki, and M. Swaminathan

Department of Chemistry, Faculty of Engg & Tech., Annamalai University, Annamalainagar-608002, India

Received 28 February 2007; Accepted 30 March 2007

Copyright © 2007 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The absorption and fluorescence spectral properties 1,5-diaminoanthraquinone (DAAQ) have been investigated in a series of organic solvents of different polarity and in aqueous solutions with Ho / pH /H in the range -10 to 17. The Stokes shifts of DAAQ are correlated with various solvent polarity scales. The better correlation of Stokes shifts of DAAQ with ET(30) indicates the predominance of hydrogen bonding interactions over dipolar interactions. The study also reveals that the fluorescence of DAAQ dication is red shifted on protonation. The abnormal fluorescence of DAAQ is found to be due to large solvent relaxation in polar medium. The acidity constants for various prototropic reactions in So and S1 states are determined and discussed.