Synthesis and fluorescence study of phenylcoumarin/cyanophenylbenzocoumarin-3-carboxylates

The absorption and fluorescence spectra of phenylcoumarin and cyanophenylbenzocoumarin-3carboxylates 6a-f and 9a-e have been investigated in chloroform, acetonitrile and ethanol. The substituting groups with varying electron donating ability such as N,N-diethyl amine and morpholine at 7-position, in phenylcoumarin-3-carboxylate 6a-f exhibits fluorescence at a longer wavelength i.e. 420-460 nm in chloroform and 460-504 nm in acetonitrile. However the morpholine derivatives 6f-j did not show fluorescence in chloroform. In another series of cyanophenylbenzocoumarin-3-carboxylates 9a-e, the compound 9c exhibits fluorescence at 546 nm in ethanol and 256 nm in acetonitrile, and lower emission wavelength i.e. 356 nm in chloroform. Further the compounds 6e, 9b, 9d and 9e exhibited high quantum yield in ethanol i.e., ΦF = 0.79, 0.70, 0.80 and 0.74 respectively compare to Rhodamine B (ΦF = 0.24) in ethanol.