Synthesis And Optical Response Performance Of Functional Molecules Containing Sulfur And Nitrogen Atoms

Organic functional materials are featured with lightweight and flexibility that makes them have promising applications in flexible electronics,particularly in foldable displays which are now becoming commercially available.The materials which display the sensitive response toward external stimuli are of great importance in information storage,environmental protection,and bio-imaging.The organic functional molecules are the key building blocks of organic functional materials.Meanwhile,the optical signals can be conveniently captured in high sensitivity.The design and synthesis of organic molecules showing optical response toward external stimuli are thus one of important gateway to develop responsive materials.We aim at the design and synthesis of organic molecules showing optical response toward external stimuli as reported in the present thesis.These functional molecules are conjugated polycycles containing sulfur?S?and nitrogen?N?atoms.The existence of N-atom brings optical responses toward acid and single-electron oxidation,and the manipulation of covalent state of S-atom shows great influence on electronic states and coordination modes.We have gain the following achievements:?1?donor-acceptor?D-A?type benzophenones were synthesized via region-selective acylation of electron-rich hetero polycycle THDTAP,then the benzophenones were employed to synthesize tetraphenylethylenes through McMurry reaction,and finally novel hetero polycycles were created via oxidative dehydrogenation cyclization of tetraphenylethylenes.?2?The intermolecular oxidative dehydrogenation coupling of THDTAP was performed to give new electron-donor 5,5'-biTHDTAP,which was then employed to construct various supramolecular assembly by complexing with guest molecules.?3?Employing Pictet-Spengler reaction as key step,we synthesized thiophene and pyridine embedded coronene,which was further transformed into star-shaped conjugated molecules.All these three types of compounds exhibit the optical response toward the external stimuli such as acid,one-electron oxidation,peroxide,and transition metal ions.Several compounds also display the high-performance optical limiting property better than C₆₀.In chapter 1,we give the brief summary on the recent progress and perspective of organic functional materials,particularly for the responsive materials containing N-and S-atoms.Meanwhile,we summarize the theory and research protocol for nonlinear optical?NLO?phenomena,the characteristic of molecules showing NLO behavior,and the organic NLO materials containing S and N-atoms.Finally,we give the hypothesis,design rationale,and research proposal of the present thesis.In chapter 2,we report the selective synthesis of D-A type benzophenones containing THDTAP moiety.The THDTAP is an analogue of phenalene containing the sp³ hybridized S and N-atoms.The two S-atoms are located at the 1-and 3-positions and the N-atom is located at the 2-position of benzene ring.Therefore,the THDTAP have two active sites for Friedel-Crafts acylation,say,N-para and S-para.By screening the reaction conditions,we successfully conducted the region-selective acylation of THDTAP to introduce various aroyls onto the N-para and S-para positions of THDTAP.The resulting two types of benzophenones are both of D-A type structures,whereas they display the different photophysical properties.It is found that the N-para type benzophenones show the reversible optical responses upon acidification and neutralization,and the acidification occurs at the carbonyls as proved by the theoretical calculations.In chapter 3,we report the synthesis and oxidative dehydrogenation cyclization of tetraphenylethylenes?TPE?containing THDTAP moiety.These TPEs were synthesized from the above-mentioned benzophenones through the McMurry reaction.Since these TPEs possess the electron-rich THDTAP moiety,the intramolecular oxidative dehydrogenation cyclization of them can be easily performed.During the oxidative dehydrogenation cyclization process,the re-arrangement reaction occurred owing to the migration of aryls.Under the oxidation of DDQ,both the two THDTAP moieties of TPEs loss one electron to give a dicationic imtermediate,which then undergoes the nucleophilic addition.Followed by the 1,2-migratory shift of THDTAP moiety and the deprotonation,the novel conjugated hetero polycycles are formed.In chapter 4,we report the photophysical properties and the responsive behavior of TPEs and their cyclization products.The above-mentioned TPEs exhibit the aggregation-induced emission?AIE?and show yellow fluorescence in aggregated states.On the other hand,the cyclization products of the TPEs display the green fluorescence in the solution and the fluorescence is quenched in the solid states.Both the TPEs and their cyclization products show the response toward external stimuli at the two active sites,N-and S-atoms.In the presence of m-chloroperoxybenzoic acid?m-CPBA?,the emissions of TPEs diminishes owing to the oxidation of the central C=C bond,whereas the cyclization products of TPEs show the fluorescence enhancement caused by the oxidation of S-atoms on THDTAP moiety.In the presence of trifluoroacetic acid?TFA?,the N-atoms on the cyclization products of TPEs are protonated to result in the intramolecular charge-transfer transition?ICT?.Consequently,their cyclization products show the red-shifts of absorption bands.It is also found that the cyclization products display the excellent optical limiting?OL?behavior with the performance better than that of the standard OL material fullerene C₆₀.In chapter 5,we report the synthesis and properties of the new electron-donor molecule 5,5'-biTHDTAP.The 5,5'-biTHDTAP show the significant red-shifts of the absorption bands from UV-region to the NIR-II window?750-1650 nm?under existence of acid,transition metal ions,and electron-acceptors.The ESR spectroscopic study shows that the N-centered cation radical is formed in 5,5'-biTHDTAP under the above conditions.A pseudo C₃-symmetric molecular cage is formed through the coordination of the S-atoms on THDTAP and transition metal ions.Furthermore,the 5,5'-biTHDTAP form the charge-transfer complexes with TCNQ and F₄TCNQ.In chapter 6,we report the star-shaped molecules containing the sp² hybridized S-and N-atoms.Employing Pictet-Spengler reaction as key step,we synthesized thiophene and pyridine embedded coronene.Taking the resulting coronene analogues as side units and triphenylamine?TPA?or 1,3,5-triphenylbenzene?TPB?as the core,the novel star-shaped conjugated molecules were created.Among these compounds,the TPA-centered and thiophene-embedded compound shows the strong fluorescence in the solution.Upon acidification and neutralization of pyridine moiety of these compounds,the absorption and emission of these compounds can be reversibly manipulated.These compounds exhibits the NLO response,and the TPA-centered ones show the better performance than the TPB-centered ones.In chapter 7,we summarize the progress and innovation points this thesis,and also give a personal perspective for this field.