Optical properties of new fluorescent iminocoumarins. Part 2. Solvatochromic study and comparison with the corresponding coumarin

The optical properties of two new iminocourmarin dyes, bearing a cyano group at the 3-position and an N-diethylamino group at the 7-position, were studied by UV-vis absorption and fluorescence spectroscopy in a large number of solvents. Dye 1 bears a free imino group, while dye 2 is substituted by an ethoxycarbonyl group on the imino function. The properties of these dyes were compared with those of 3-cyano-7-diethylaminocoumarin (3). The study shows that the three compounds display close spectroscopic behaviour in a large range of solvents, but the iminocoumarins exhibit much better fluorescence efficiency than the coumarin in polar and moderately protic solvents. This shows that iminocoumarin derivatives can advantageously replace coumarins in this type of solvents, and confirms that substitution on the imino group is a convenient way to obtain good fluorescent probes designed for various purposes. (C) 2006 Academic des sciences. Published by Elsevier SAS. All rights reserved.