| Chirality is one of the structural characteristics of chemical and biological organic molecules.Chirality was originally used to describe a spatial structure that cannot completely coincide with one's own scene.Then,in order to better understand the chiral structure,the researchers developed chiral spectroscopy techniques.For example,electronic circular dichroism(ECD)is mainly used in the chiral application of chromophores,and Raman optical activity(ROA)represents the optical properties of the vibrating groups.The combination of the two spectra can help to better understand the chiral characteristics of the molecule.In the first research content of this article,we visually studied the chiral spectral characteristics of norascyronone C,a new polycyclic polyprenylated acylphloroglucinols(PPAPs)derivative with a highly oxygenated phloroglucinol core.The one-photon and two-photon spectra of norascyronone C,ECD spectra and ROA spectra under different scattering directions were calculated and simulated,and the correlation between chiral features and spectral information was investigated.First,by calculating the transition density matrix diagram and charge density difference diagram of the simulated norascyronone C,the interaction between the transition electric dipole moment,the transition magnetic dipole moment,the transition electric quadrupole moment and its tensor product is visualized.It shows that the intensity of electromagnetic interaction is related to local excitation or photo-induced charge transfer.Then,the ROA spectra were further calculated and simulated.In order to explore whether the response of Raman photoactivity is related to the molecular structure,we analyzed the relationship between the chirality of the chromophore and the molecular vibration mode.It was finally discovered that the ROA spectral inversion phenomenon was mainly related to the anisotropy exhibited by the molecular chromophore at the dipole moment density under the excitation of a specific wavelength of excitation light.In recent years,the application of typical third-order nonlinear optical effects(two-photon absorption(TPA)has gradually become a trend.Because the probability of occurrence of TPA is lower than that of one-photon absorption(OPA),the probability can be increased by adjusting the cross-sectional size.Therefore,it is necessary to design molecules with large TPA cross-sectional characteristics in the field of chemistry to enhance the two-photon absorption process.Researchs have shown that the transition efficiency of the dimer system can be controlled under the action of an external electric field,thereby affecting the charge transfer efficiency between molecules,which has practical research significance in improving the photoelectric conversion efficiency.The second research content of this article,we explored the charge transfer characteristics of the D-B-A system in two-photon absorption under the control of an external electric field.Through the analysis of the strong absorption peaks in the TPA spectra of the porphyrin-tetra-thiophene-fullerene complex under the condition of an external electric field,the results show that the sequential charge transfer and super charge transfer during the TPA process of the complex can be promoted by adjusting the direction and intensity of the external electric field.In the two-step transition process of TPA in the current system,it is found that when the direction of the electric field is the same as the direction of the donor pointing to the acceptor,the strength of the charge separation is strong at this time after observing the density matrix and the charge differential density map,and the phenomenon of super exchange charge transfer is prone to occur;on the contrary,the phenomenon of charge recombination may also occur.It shows that this kind of macroscopic electric field regulation can promote or inhibit the charge transfer in different directions on the atomic scale. |
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