| With the increasing progress of society today,the concept of "green health"has been deeply rooted in people's hearts.Phytoestrogens of natural origin have gradually entered the public view due to their special effects.Studies have found that phytoestrogens have important effects on plants and humans,and their extraction,preservation,and functioning are all affected by an important factor-"light".This paper mainly selects the parent molecules of two types of phytoestrogens,and explores their photoreaction mechanism through theoretical calculations in order to provide help for their effectiveness.The parent molecule of the stilbene phytoestrogen resveratrol is stilbene.It is usually a type of plant antitoxin synthesized by plants themselves,used to resist the invasion of harmful pathogens or environmental pressure.At the same time,its parent molecule stilbene is related to the primary stage of biological vision.We explored the photoisomerization process of cis-stilbene molecules by combining electronic structure calculations and non-adiabatic kinetic simulations.The results are as follows:(1)Static electronic structure calculations show that the S1 state of cis-stilbene is bright,and the system has a relatively flat S1 state potential energy surface in the Franck-Condon region.(2)We obtain three S1/S0 conical intersections(CI)and propose two non-adiabatic deactivation paths to effectively return the system to the ground state.In the first pathway,when the light is excited to the S1 state,cis-stilbene advances along the S1 potential energy surface and quickly reaches the S1 minimum.Thereafter,the molecule tends to isomerize around the central C=C double bond until it encounters the S1S0-C cone intersection,at which the system decays to the ground state.Another approach involves the S1S0-D cone intersection from which the S1 system decays to the ground state and produces a photocyclization product.(3)In addition to the mechanism information,we also estimated that the lifetime of the excited state of S1 is 600.0 fs,and three products(cis,trans isomer,and DHP)were obtained at the end of the 2 ps simulation time.Through the above studies,we have clearly explained the photochemical reaction mechanism of stilbene in theory.It is worth noting that the theoretical calculation results are highly consistent with the experimental results.Therefore,we have transferred our successful research experience to the study of the photoreaction mechanism of another important type of phytoestrogens,namely the quercetin parent molecule,3-hydroxyflavonoids.Quercetin can be used as a plant virus agent to control plant virus diseases;because its parent molecule is easy to induce dual fluorescence phenomenon,which is conducive to plant color and photosynthesis.The study found that the 3-hydroxyflavonoid molecule is bright in the Frank-Condon region of the S1 excited state,and the electronic transition from the S0 ground state to the S1 excited state mainly comes from the singlet excitation of HOMO-LOMO.Comparing the S0 ground state,S1 excited state structure,and HOMO and LUMO molecular orbitals,we can speculate that in the process of the decay from the excited state to the ground state,intramolecular proton transfer may occur in the excited state.At the same time,we also obtained the maximum absorption wavelength and vertical excitation energy,which are consistent with the experimental results.With the development of science and technology,we can not only explore the photochemical and photophysical properties of molecules experimentally,but also perform relevant verification and prediction in theory,so as to provide some theoretical guidance for experiments.In this study,quantum chemistry research methods were used to explore the photophysical and photochemical properties of the resveratrol parent molecule stilbene and quercetin parent molecule 3-hydroxyflavonoids,which provided a study of the photoreaction mechanism of phytoestrogens parent molecules ideas. |
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