Experimental And Quantum Chemistry Calculation Studies On The Raman Spectra Of Binaphthyl Diamine

The axially chiral binaphthyl compounds play a crucial role in constructing new stable chiral structures as well as in developing effective asymmetric organocatalysts.Various spectroscopic methods,such as the electronic absorption,IR absorption and Raman scattering,have been used to explore the structures and properties of the binaphthyl compounds in the past several decades.Among various binaphthyl compounds,the 1,1'-binaphthyl-2,2'-diamine(BINAM)derivatives have been found highly useful in developing new asymmetric catalysts.On the other hand,despite of its significance in asymmetric catalysis,the vibrational spectroscopic properties of BINAM have not well studied.To the best of our knowledge,the experimental and theoretical study of Raman spectrum of BINAM has not been reported.Therefore,the present study was conducted with the intention to fill this blank.Chapter 1 briefly introduces the fundamental knowledge of quantum chemistry calculation,Raman scattering spectroscopy,and vibrational optical activity.The research background of this dissertation is also introducedIn Chapter 2,we have studied the IR absorption,visible excited normal Raman,and UV-excited near-resonance Raman spectra of 1,1'-binaphthyl-2,2'-diamine(BINAM).Density functional theory(DFT)calculations were carried out to study the vibrational frequencies and the ground-state structure of BINAM.The measured IR and Raman spectra of BINAM were found in well accordance with the calculations.The assignments of observed IR and Raman bands were proposed on the basis of the calculated and measured frequencies and intensities.In comparison with the visible excited normal Raman,several bands of BINAM were found dramatically enhanced in the UV resonance Raman spectrum.Possible excited state structure distortion was discussed based on the RR intensity analyses.In Chapter 3,we theoretically studied the ECD,VCD and ICPu-ROA spectra of chiral R-BINAM with density functional theory calculations.It was found that the intensities of most of VCD bands in the 800-1650 cm-1 region can be well explained with the degenerate coupled oscillator model.The intensity distribution of ICPu-ROA was found significantly different from that of ICP-Raman,which reflects the difference of physical mechanisms of the two spectroscopic techniques.The intensity patterns of Raman and ROA were discussed from the points of view of the Raman and ROA tensors as well as the atomic displacements of the normal vibrational modes.It was proposed that the considerably large ROA absolute intensities for the v9'/v9 modes of R-BINAM are due to the fact that these modes can effectively couple the electron circulation around the C2 axis of the molecule,which produces a large anisotropic magnetic dipole polarizability.