Research On The Synthesis And Fluorescent Properties Of Coumarin-chalcone Derivatives

Coumarin-chalcone has ? conjugated system. Due to the over lapping of ? orbital,delocalization of electronic charge distribution leads to a high mobility of the electron density.What's more, the presence of appropriate terminal electron donor or acceptor groups on aromatic rings of chalcone can enhance the asymmetric electron distribution in either or both ground and excited electron states leading to large molecular hyperpolarizabilities, which greatly improves the fluorescence performance. Because of the wide application in pesticides,optical brighteners, cosmetics and food additives, the synthesis of coumarin-chalcone derivatives have attracted much attention of chemists. Thus, three series of coumarin-chalcone derivatives were synthesized in this thesis, and the influence of the changes of molecular structure on the fluorescent properties was preliminarily discussed. The thesis mainly includes three parts:The first part introduced the application of the coumarin-chalcone as fluorescent whitening agent, dye laser and their antitumor, antimalaria, antifungal and antiviral activities and so on. Then, the synthetic methods of coumarin-chalcone compounds such as solution synthesis, microwave-assisted synthesis and green synthesis were summarized.The second part: Firstly, using salicylaldehyde and ethyl acetoacetate as raw materials,3-acetylcoumarins were achieved by Knoevenagel reaction. Then, 3-acetylcoumarin underwent Claisen-Schmidt reaction with different substituted benzaldehydes to afford the corresponding coumarin-chalcone products 2a-2f and 8a-8c. Secondly, 4-diethylamino salicylaldehyde was used as raw materials and subjected to Wittig reaction to give the coumarin-3-aldehyde, which reacted with different substituted acetophenone by Claisen-Schmidt reaction to provide the corresponding coumarin-chalcone derivatives 6a-6d.In the above-synthesized coumarin-chalcones, 2a-2d and the corresponding 6a-6d are isomers each other. The former are 1-coumarinyl-3-phenylpropenone compounds, the latter belong to1-phenyl-3-coumarinylpropenone compounds. They have similar molecular structure, but the positions of the double bond and carbonyl group occurr swaps. These synthesized compounds were characterized by IR, NMR and MS methods.The third part: Through measuring the UV–vis absorption spectra, fluorescence emission spectra and fluorescence quantum yields of the three series of coumarin-chalcone derivatives,the relationship between the molecular structure and optical properties was explored preliminarily. Compared to the parent 3-acetylcoumarin and 3-formylcoumarin, the three series of compounds were resulted from the introduction of chalcone moiety with different substituents to the parent structure, which leaded to the extension of conjugate system, so the UV-Vis absorption and fluorescence emission peaks were all red-shifted. Compared to thecoumarin-chalcones each other in the same series, the influence of substituents on benzene ring on the absorption and emission spectra was not obvious. However, compared with compounds 2a-2d, the UV-vis absorption and the fluorescence emission maxima of the corresponding isomers 6a-6d were significantly red-shifted, and the fluorescence quantum yields were obviously improved, respectively. This revealed that compounds 6a-6d perhaps have better molecular plane and have better intramolecular charge transfer properties compared to the corresponding isomers 2a-2d.