2231–4202  (Print)                
2249–9970  (Online)             
Peer Reviewed and Refereed Journal

JPAST is a Peer Reviewed & Refereed biannual multidisciplinary journal starting from July 2011. Articles are invited for Dec 23 issue.
Volume 5, Issue 2, Pages 33-37, July 2015

Effect of Solvents and Substituents on the Fluorescence Behaviour of Coumarin Dye Lasers

Rajesh Giri

Department of Physics and Electronics

Rajdhani College, University of Delhi, New Delhi, India.


In order to investigate the effect of solvents and substituents on the fluorescence behaviour of coumarin derivatives the absorption and fluorescence emission spectra of 4–phenyl substituted coumarins namely: 4-phenyl-7-hydroxy coumarin (1), 4-phenyl-7-methoxy coumarin (2), 4-phenyl-6-hydroxy-7-methoxy coumarin (3), 4-pheny-6,7-dimethoxy  coumarin (4) and 4-phenyl-6,7-dihydroxy coumarin (5) have been studied in various organic solvents of varying dipole moment. It was found that in a given solvent the position of the absorption and fluorescence maxima depends on the nature and position of the additional substituent group linked to the 4-phenyl coumarin and the wavelengths shifts obtained are interpreted in terms of the changes in the mobility of π electrons. From the fluorescence emission spectra of the present coumarins it was found that the 4-phenyl coumarins are less fluorescent and show a smaller change in polarity on excitation as compared to the corresponding 3- henyl derivatives. These changes are interpreted in terms of the possible resonance structures of the coumarin derivatives.

Keywords: Fluorescence, Dipole moment, Resonance structures.

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