The Study On The Circular Dichroism Spectrum Of The Chiral Porphyrin Supramolecular

Supramolecular chemistry as a chemical science frontier area has been well developed. Chirality is closely related to life activities in the nature. So chiral supramolecular has widely application. And chiral porphyrin supramolecular that built on porphyrins with special characteristics and properties has become a research hotspot because of potential applications in the fields of materials science, molecular devices, biomedical, etc. Properties and application of chiral porphyrins supramolecular is closely related to the molecular configurations, but the conformation is easily affected by various internal or external factors, and is protean in solution. Circular dichroism(CD) spectrum as one of the most effective tools to determined chiral molecule stereo configuration can solve this problem. Theoretical simulation CD spectrum changes can not only play a guiding role and prediction effect on the synthesis, molecular design but also promote the theoretical analysis and improve calculation model. But now experimental research is the most common way to research chirality porphyrin supramolecular CD spectra, theoretical simulation is seldom reported. So theoretical simulation of the CD spectra with different configurations and of the influence of various factors on configurations has became a pressing issue.Based on the above reasons, the CD spectra of series of flexible and semi-flexible chiral porphyrins supramolecular were studied. Firstly, the CD sprctra of a series of chiral amino acids bridded bis-porphyrin compounds and the recognition of ethylenediamine guest were studied qualitatively by molecular mechanics(MM) in Hyperchem software and molecular dynamics(MD) method in Gromacs software. We have successfully simulated the inversion phenomenon of the CD spectra with 1:1 host-guest stoichiometry and give theoretical explanation combined with exciton coupled theory. This has proved the reliability of MM and MD method to simulate chiral porphyrin supramolecular CD spectra. This provides a reliable theoretical simulation method to simulate the flexible supramolecular conformation and CD spectra under different stoichiometry.The second part is the quantitative calculation to CD spectrum of a series of chiral binaphthyl bridged bis-porphyrin compounds. The quantitative calculation was based on the theory of exciton coupling and three models of De Voe polarization theory. It is worth mentioning that the specific calculation method is based on the calculation results of porphyrin monomer. Two-peaks fitting and the redistribution of intensity were used to calculate CD spectrum through the results of porphyrin monomer. It is concluded that the calculation CD spectrum is asymmetry and well accordance with experimental spectrum. The most suitable model of para porphyrin, meta porphyrin, ortho porphyrin were respectively hybrid model, circular oscillator model and the effective dipole moment. This results indicates that the guiding role of porphyrin monomer calculation to the CD spectrum calculation. So the analysis of porphyrin monomer before CD spectrum calculation is necessary, which provides a method to guide the calculation of CD spectra, makes calculation model more targeted and enrich the theoretical calculation method.