Studies On The Synthesis And Spectra Properties Of Novel Coumarins

Five series of novel coumarins were synthesized by palladium-catalyzed reaction and the structures were characterized by IR, NMR, EA, MS and X-ray diffraction. The absorption-emission spectra and fluorescence quantum yields were determined and the relationships between molecular structure and fluorescence properties were also studied.3-Stilbenylcoumarins were synthesized by Pd(OAc)2-catalyzed Heck reactionusing TOP as ligand in DMF. Determination of 3-(4'-chlorostilben-4-yl)coumarin's single crystal by X-ray diffraction showed that the newly formed olefin was a trans structure and that the hedral angle between the coumarin skeleton and near benzene ring of the stilbene was 42.66 , but that the coumarin skeleton and the far benzene ring were on almost the same plane. Compared to its open-chain analog, 3-(4'-chlorostilben-4-yl)coumarin rigidified by lactone produced a considerably enhanced fluorescence quantum yield and a large bathochromic shift in the emission maximum but little change in absorption. Study of the 7-diethylamino-3-stilbenylcoumarin series prepared in this paper showed that 4'-Cl-substituted stilbenylcoumarin had a higher fluorescence quantum yield than the others in that series.Four 3-diphenylacetylenylcoumarins were prepared by Pd(PPli3)2Cl2-catalyzed Sonogashira reaction. Compared with their corresponding 3-stilbenylcoumarins, they had blue shifts in the absorption and emission spectra and lower fluorescence quantum yields. With the introduction of electron donor (-NEta) at the 7-position of any of these compounds, there was only a slight difference in the absorption and emission maxima of these 7-NEt2-substituted coumarins. However, the diphenylacetylene-extended 7-NEt2-substituted coumarin did have a higher fluorescence quantum yield, which may be attributed to the efficient electronic communication of the structure's triple-bond cylindrical symmetry.Four alkylacetylenyl-substituted coumarins were synthesized by palladium-catalyzed Sonogashira reaction and two 2-benzofuran-substitutedcoumarins were synthesized by palladium-catalyzed cycloaddition of 2-iodophenoland terminal acetylenylcoumarin in relatively high yields. Study of the spectra characteristics showed that 2-benzofuran-substituted coumarin without any substituent at the 7-position had a low fluorescence quantum yield, but that with the introduction of the electron-donating diethylamino at its 7-position, the fluorescence quantum yield increased considerably.Seven 7-styrylcoumarins were synthesized by palladium-catalyzed Heck reaction of coumarin diazonium salts with substituted styrenes. These reactions yielded well under mild conditions. Introducing a strong electron donor (-NEt2) at the p-position of 7-styrene caused a significant bathochromic shift of the absorption maximum, while a weak electron-donor (-CHa) or an electron-acceptor (-CN) produced little change. Bathochromic shifts of the emission maxima also occurred and increased with the enhancement of the substituent's electron-donating ability. The p-CH3 and p-CN substituted styrylcoumarins had higher fluorescence quantum yields than the other styrylcoumarins.7-Phenylacetylenylcoumarins prepared from 4-methyl-7-iodocoumarin and substituted phenylacetylene by Pd-catalyzed reaction had similar fluorescence quantum yields as the corresponding 7-styrylcoumarins, with blue shifts in absorption and emission maxima, except that strong electron-donating diethylamino substituted 7-phenylacetylenylcoumarin had a higher fluorescence quantum yield than the corresponding 7-styrylcoumarin and they both produced yellow fluorescence in THF in contrast to the blue fluorescence produced by 4-methyl-7-diethylamino coumarin in THF.