Synthesis of coumarin based fluorescent compounds

The reaction of different 7,8-disubstituted coumarin 4-acetic acids with 7-diethylaminocoumarin-3-carbaldehyde in the presence of piperidine in methanol gives highly fluorescent (E)-1-(7-diethylaminocoumarin-3-yl)-2-(7,8-disubstituted coumarin-4-yl)ethenes in good yield. Only the (E) diastereomers of these are obtained. The compounds are new, orange to red in colour and show emission in yellow to red region. These compounds were further studied for their emission properties.