Charge Transfer Theoretical Study On Photochromic Materials Thiophene[3,2-b]phosphorus Oxide

In recent years,photochromic materials have been widely used in various fields such as photosensitive materials and electronic information storage due to their unique properties.Since visible light is relatively destructive and harmful to various optical devices and biological cells,photochromic reaction under visible light irradiation has also become a hot issue.Phosphors have potential applications in optoelectronics due to their unique structure and tunable photophysical properties.The novel thieno[3.2-b]phosphorus heterocycle described in this paper can achieve photochromic reaction under visible light irradiation,and it has the advantages of good thermal irreversibility and excellent fatigue resistance.At the same time,it also has a relatively high photoelectric conversion rate.Incorporating differentπsystems into the phosphor backbone of thieno[3.2-b]phosphahal oxide 1-5affects the charge transfer process of these molecules,thereby changing their properties.Molecule 1 incorporates a thiophene（C₄H₄S）on the phosphor backbone,molecule 2 incorporates benzothiophene on the phosphor backbone,molecule 3 is incorporated into the phosphor backbone and dithiophene,molecule 4 On the basis of molecule 2,an electron-rich diphenylamine NPh2 is added to the phosphor backbone,and molecule 5 is a benzene ring incorporated on the phosphor backbone on the basis of molecule 3.While studying the excited state properties of these five molecules in vacuum,the five molecules were placed in the solvent environment of acetonitrile（CH₃CN）,tetrahydrofuran（THF）and toluene,and the solvent environment and solvent itself were determined by comparison.How does the polarity affect the charge transfer of molecules 1-5?In the research process,we use quantum mechanics as the theoretical basis and use the density functional method.First,we optimize the five molecular structures through Gaussian09 and other related calculation software to make the molecular structure more stable,and then we can calculate the molecule 1-5 The difference between the highest occupied orbit（HOMO）and the lowest unoccupied orbit（LUMO）in the excited state,and the corresponding absorption spectrum can be drawn.It is found that the energy level difference gradually increases with the extension of theπsystem on the phosphor backbone.Decrease,the absorption spectrum is red shifted.Then compare the transition dipole moments of the molecules 1-5 in vacuum and three different solvent environments,and draw the molecular transition density map（TD）and the charge difference density map（CDD）to observe the charge transfer more intuitively..Finally,Multiwfn software was used to analyze the electron cloud density of molecules in different solvents.It was found that the molecules in the above solvent environments did promote charge transfer,and the increase of solvent polarity was more favorable for charge transfer.