Design,Synthesis And Photoelectric Physical Properties Of D-A Molecules With THDTAP As Electron Donor

The D-A molecule with electron donor and electron acceptor have been investigated extensively and applied in the fields of organic field-effect transistors,organic light-emitting diodes,and organic solar cells.Electron transfer?ET?or charge transfer?ICT?processes can occur between donor and acceptor in a D-A molecule,which is an important pathway of the deactivation of molecular excited states.The properties of electron donor and acceptor in the molecule can alter the intramolecular electron or charge transfer process and have a significant effect on the photoelectric physical properties of the molecule.Therefore,the design and synthesis D-A molecular system that containing multi-step adjustable electron donor or acceptor is of great significance for investigating the molecular push-pull electronic effects and applications.The incorporation of sulfur and nitrogen atoms into the D-A molecule can modulate the properties of the molecule effectively:on the one hand,both the S atom and the N atom contain a lone pair of electrons,which can participate in the molecular conjugated system,and enhance the electron donating ability of the electron donor,then promote the intramolecular charge transfer process.On the other hand,the valence state of S atom is multiple and it can be oxidized to sulfoxide and sulfone under appropriate conditions gradually.N atom can be protonated to form corresponding ammonium salts.By these two methods,the electron donating ability of the electron donor can be attenuated carefully,and the intramolecular charge transfer process can be inhibited,thereby adjusting the photophysical properties of the molecule.THDTAP is an excellent electron donor and possesses a strong electron donating ability due to the introduction of two sulfur atoms and one nitrogen atom.In this thesis,we designed and synthesized three types of D-A molecules whose electron donor and acceptor were connected by a single bond,with THDTAP as electron donor,BODIPY,terpyridine,benzimidazole skeleton as electron acceptor respectively.The following three new results have been achieved by the study of these D-A molecules:?1?We have achieved the adjustment for the electron donating ability of THDTAP by oxidation of S and protonation of N atom,and then modulated the ICT/PET process of BODIPY D-A molecules,finally tuned the performance of photoelectric;?2?We have achieved the modulation of the ICT process of the terpyridine ligand and the interaction between the ligand and the metal ion by oxidation of S atom in THDTAP,and resulting selective recognizing the metal ion by the ligand;?3?The protonation of amidine N?sp²?atom enhanced the ICT process without reducing the electron donating ability of THDTAP and brought about the ET process.Furthermore,the photoelectric properties were accordingly tuned.The details are as follows:Chapter 1,the literature research.A briefly introduction of development status of functional organic materials,especially functional organic small molecule materials containing S and N atoms was made.Summary of the research and application of materials containing S and N atoms was presented and accompanied by an introduction of the role and mechanism of sulfur and nitrogen atoms performed in the regulation of D-A molecules properties.Finally,we put forward the strategies and basic ideas of this thesis.Chapter 2,the synthesis and oxidation of D-A type BODIPY compounds with THDTAP as electron donor.An appropriate synthesis method was selected to efficiently prepare D-A molecules with THDTAP as electron donor and BODIPY as electron acceptor.The sulfur atoms of the THDTAP moiety was oxidized by m-chloroperoxybenzoic acid and five oxidation products were obtained with high yield.Their electrochemical properties are consistent with theoretical calculations:say,the oxidation of sulfur atoms reduced the HOMO orbital energy level effectively and adjust the molecular energy gap without affecting the LUMO orbital energy level.Chapter 3,the photophysical processes and external stimuli responses of D-A type BODIPY compounds with THDTAP as electron donor.The intramolecular charge transfer process of these compounds is studied systematically.Solvent effect model studies show oxidation of sulfur atom can modulate the degree of charge transfer accompanying by the fluorescence off-on switch and blue shift.The theoretical calculations and femtosecond transient spectroscopy results have clarified this point subsequently.In addition,the protonation and electrochemical oxidation of nitrogen atoms also accomplished the modulation of intramolecular charge transfer or photoinduced hole transfer.The emission off-on switch and blue shift can be observed,and the fluorescence quantum yield was also changed significantly.At last,the effect of polymorphism on the solid-state luminescence was discussed.Chapter 4,the energy transfer process of BODIPY compounds containing THDTAP moiety.Another microscopic process:the energy transfer process is explored.Combining with the exciton coupling theory,a basic vector model was established,and the effect of the energy transfer process on the luminescence properties molecular was presented.Finally,it was verified by theoretical calculation and polarization fluorescence experiment.Chapter 5,the synthesis and properties of D-A type terpyridine compounds with THDTAP as electron donor.A D-A molecule with THDTAP as electron donor and terpyridine as electron acceptor was constructed.The sulfur atom of the THDTAP moiety was oxidized by m-chloroperoxybenzoic gradually and five oxidation products were obtained with high yield.The intramolecular charge transfer process of the ligand and the charge transfer process between the ligand and the metal ion is modulated by means of the oxidation of sulfur atoms,thus the properties of the coordination compound been adjusted.In the end,we found that metal ions Zn²⁺,Cd²⁺,and Ag⁺can be recognized stepwise by employing two of these molecules as fluorescence probes.Chapter 6,the synthesis and properties of D-A type amidine polycyclic compounds with THDTAP as electron donor.The D-A molecule with THDTAP as an electron donor,and amidine polycyclic as electron acceptor was constructed.The protonation of the N atom of the amidine N?sp²?enhance the electron-withdrawing ability of the electron acceptor in the molecule,modulates push-pull electron effect of the molecule,and lead to the transition of the intramolecular charge transfer process to the electron transfer?ET?process.The effects of different amidine ring systems on charge transfer and electron transfer processes were also discussed.Chapter 7,the summary and outlook.We summarize the work of this thesis,sort out the problems that have emerged or not solved in the course of the research,and clarify the direction of the follow-up work.