Synthesis and spectroscopic study of new biscoumarin dyes based on 7-(4-methylcoumarinyl) diesters

A liquid/liquid interfacial technique was used to prepare biscoumarin dyes by condensing 7-hydroxy-4-methylcoumarin with various diacyl chlorides in the presence of a phase-transfer catalyst such as triethylbenzylammonium chloride. The reaction conditions were optimized. Six new biscoumarin derivatives were thus prepared in high yield. Their optical properties were studied in chloroform by UV/vis absorption and fluorescence spectroscopies. It appeared that the shape of the absorption spectra varies with the nature of the tether between both chromophores. In contrast, the excitation and emission spectra were almost unchanged, although the compounds exhibited drastic differences in their fluorescence efficiency.