| This dissertation describes the synthesis of a new type of ICT fluorophors,benzanilides,and the study of their absorption spectra,fluorescence spectra,electronic effect,steric effect and intramolecular charge transfer (ICT). It consists of four chapters:introduction,chapter two,chapter three,and the conclusions and prospects.In chapter one,the discovery and development of the ICT fluorescence theory and application were briefly reviewed. It also concisely illustrated the advances in the recent photophysical and photochemical research of benzanilides. The research proposal for this dissertation was presented.In chapter two,several series of benzanilides(MBAs) were synthesized and characterized. This chapter was divided into two sections. In section one,we changed the positions of methyl group at aniline moiety to introduce the steric effect on benzanilides. We synthesized series of para- and weta-substituted benzoyl para-,meta and ortho-methyl benzanilides as well as ortho,ortho-dimethyl benzanilides (X-MBAs). These compounds were purified by repeated recrystallization from acetone and were characterized by IR.In section two,on the basis of section one,we used another way to introduce the steric effect on benzanilides by changing the positions of methyl group at benzoyl moiety. The procedures for the synthesis of a series of para-,meta and ortho-methyl as well as ortho,ortho-dimethyl benzoyl para- and meta-substituted benzanilides (Y-MBAs) were described. These compounds werealso purified by repeated recrystallization from acetone,and characterized by IR.In chapter three,the photophysical properties of the synthesized benzanilides(MBAs) were studied. This chapter contained five parts. In part one,we briefly deduced the linear relationship between the emission energies of the long-wavelength fluorescence of ICT fluorophors and the Hammett substituent coefficient a,and concisely discussed its significance. Part two described the experimental details.In part three,we investigated the synthesized benzanilides' absorption spectra in cyclohexane and anhydrous diethylether. On the whole,the polarity of the solvent did not affect the absorption spectra of the same benzanilide molecule,and the variation of the substituents at the benzoyl moiety did not influence the ground structures of the MB As,their absorption maxima and spectral profiles. However,the steric effect distinctly affected the MB As' absorption spectra. In part four,the MBAs' fluorescence spectra were measured in cyclohexane and anhydrous diethylether. It was observed that almost all of the synthesized compounds displayed an abnormal long-wavelength fluorescence at around 500nm in cyclohexane. The long-wavelength emission of X-MBAs shifted strongly to the red with increasing electron-withdrawing ability of the substituent at the benzoyl moiety,while the long-wavelength emission of Y-MBAs shifted to the red when aniline moiety was substituted by a decreasing electron-withdrawing substituent. In anhydrous diethylether,the long-wavelength emission of the synthesized benzanilides shifted to the red more strikingly than in cyclohexane because of its higher polarity,and some of the synthesized compounds' fluorescence were even quenched. In our experiments,the emission energies of the long-wavelength fluorescence of both X-MBAs and Y-MBAs in cyclohexane were found to vary linearly with the Hammett substituent coefficient a. It was concluded that the long-wavelength emission of MBAs in cyclohexane originated from the intramolecular charge transfer state. This was the direct spectroscopic evidence for the charge transfer nature of the long-wavelength emission of MBAs in cyclohexane. The especially significant observation was that the position of the methyl group at the aniline or benzoyl moiety hardly affected the slope of the Weller-Hammett equation of MBAs. This meaned that the steric effect hardly influenced the electronic effect of the MBAs and their ICT emission mechanism. But it obviously affected the interception of the MBAs' Weller...
|
PDF Full Text Request