Preparation And Optical Properties Of Donor-Acceptor Dyes Connected By Dynamic Covalent Bonds

In this thesis,three donor-acceptor dyes linked by Diels-Alder dynamic covalent bond were designed and synthesized,and their optical behavior and dynamic covalent chemical properties were investigated.These three dyes contain carbazole /triphenylamine / perene and dansyl double fluorescent chromophores,and there is intramolecular fluorescence resonance energy transfer.The chemical structures of three maleimide-furan dyes based on Diels-Alder dynamic covalent bond were fully characterized.The synthesis of these three functional molecules is based on efficient,mild,clean and no side effect Diels-Alder addition.The effects of 1,3 and 1,4substituents of furan on the activity of Diels-Alder addition are discussed.The optical behaviors of the donor-acceptor dyes and their donor,acceptor parts were investigated by UV-vis absorption spectra and fluorescence emission spectra.The UV-vis absorption and fluorescence emission spectra,three-dimensional fluorescence spectra and time-resolved spectra of the donor-acceptor dyes show that intramolecular fluorescence resonance energy transfer occurs from carbazole /triphenylamine / perene to dansyl chromophore.The calculated transfer efficiencies are 94.9 %,38.6 % and 64.0 %,respectively.Intramolecular energy transfer results in the large Stokes shifts of these donor-acceptor dyes,and their fluorescence emission is highly sensitive to environmental polarity.With the increase of solvent polarity,the fluorescence spectra of donor-acceptor dyes are red shifted,which proves their potential as new fluorescent resonance energy transfer probes.The results of single crystal X-ray diffraction show that the Diels-Alder dynamic covalent bond is easy to break and reformation.The dynamic covalent chemical properties of donor-acceptor dyes were investigated,and linked with energy transfer.It was found that their energy transfer could be regulated by the reversible formation and breaking of dynamic Diels-Alder covalent bond,and these two kinds of energy transfer systems could be transformed by dynamic exchange experiments.In addition,a new white light emission was obtained through the dynamic exchange experiment.