Theoretical Study On The Structure-Photophysical Property Relationship Of Phenothiazides Derivatives

Phenothiazine derivatives have long been used in psychiatry due to their unique biochemical properties.In recent years,the application of such derivatives in the field of photoelectricity(such as optical sensing,fluorescent probe,dye sensitizer,organic light-emitting diode,optical switch,etc.)has been very eye-catching.The phenothiazine derivatives can possess a variety of photophysical properties thanks to their structural characteristics: the phenothiazine precursor contains electron-rich N and S atoms,which makes the other chromophores of phenothiazine easy to have strong electron donation capacity;The central heterocyclic ring is a butterfly structure,which has a large non-coplanar curvature in the ground state,and can effectively reduce aggregation-induced quenching when forming a polymer or a crystal;The central heterocyclic ring has many active sites,and it is easy to adjust its photophysical properties by substitution modification.Among the many phenothiazine substitutions,N-10 and C-3(or symmetric C-7)are the most active substitution sites,and a large number of N-10 and C-3 substituted phenothiazine derivatives with various optical properties have been experimentally synthesized,but there are relatively few theoretical studies on the number of regularities of these derivatives.Systematic structure-photophysical properties study of a certain number of regularly substituted phenothiazide derivatives is beneficial to further optimize and design new phenothiazine-based chromophore and probe.In this paper,nearly 20 kinds of phenothiazine derivatives with N groups,C-sites,N-sites and C-sites substituted by different groups were selected as the research objects,using density functional theory and time-dependent density functional theory.Theoretical studies on structure,absorption spectroscopy,emission spectroscopy,Stokes shift,radiation/non-radiative efficiency,charge transfer and other aspects have been carried out,discussed the active site alone replaced the source of the optical properties change and the synergistic effect between different active site instead.The paper is divided into several chapters: The first chapter briefly introduces the source of phenothiazine and the application of phenothiazine derivatives in photovoltaic materials,drugs and dye-sensitized solar cells.In addition,it also introduces the meaning of the work done in this article.The second chapter introduces in detail the theoretical methods used in this paper,density functional theory and time-dependent density functional theory.The third and fourth chapters discuss the opticalproperties of the phenothiazine derivatives substituted at the N position,the C position,and the C/N position,respectively.The main conclusions we obtained are as follows:(1)The alkyl chain and the aromatic ring are substituted at the N-10 position,and the wavelength is mainly affected by the central heterocyclic ring.The absorption wavelength and the emission wavelength are limited,when the alkyl chain is replaced by butane,the wavelength tends to converge,and the red shift value of absorption wavelength is about 20 nm.The emission wavelength of the naphthalene ring-substituted phenothiazine derivative is significantly longer,and a significant charge transfer occurs.(2)The aromatic amine,phenol,pyridine ring and small organic molecules are substituted at the C-3 position,and the molecular spectrum is changed by the planar transformation and charge transfer of the heterocyclic ring.The results show that the spectrum is significantly prolonged and the vibrator strength is significantly increased.The Stokes displacement increases.When the C-3 position is substituted by cyanoacrylic acid(PTZ-12),the charge transfer is very obvious,the absorption and emission wavelengths are significantly prolonged,the emission wavelength is red-shifted up to 303 nm,and the Stokes shift is at most 297 nm.(3)When the N-10 and C-3 positions are simultaneously substituted by an alkyl chain and an electrophilic group,a synergistic effect occurs.The maximum emission wavelength is 351 nm red,and the Stokes shift is the largest 354 nm.(4)On the basis of the analysis in the previous section,the alkyl chain containing sulfur element is substituted at the C-2and C-8 positions,the planarity of the heterocyclic ring is almost unchanged,and the absorption and emission wavelengths are prolonged.(5)The calculation results also show that the solvent polarity has little effect on the stable configuration and absorption spectrum of the phenothiazine derivative,but the emission spectrum and the molecules with obvious charge transfer are still sensitive to the polarity of the solution.(6)The C-3 position substitution has a higher radiation rate and quantum yield than the N-10 position substitution.In summary,the theoretical study on the photophysical properties of phenothiazine derivatives provides a solid theoretical basis for further optimization and design of phenothiazine-based fluorescent dyeing and dye molecules.