Design,Synthesis,Optical Properties And Applications Of Alkynyl Conjugated D-A Type Aromatic Amines Derivatives

Conjugated organic molecules with D-A(D is electron donor,A is electron acceptor)structure have tunable photoinduced electron transfer properties,and are widely applied as organic photoelectronic materials.Studying the relationship between the structure of electron donors and acceptors in the D-A type conjugated molecules and the photo-induced electron transfor capacity are very important for the structural designing and application of D-A type conjugated organic molecules.Therefore,a series of acetylene bridged D-A type molecules with outstanding intramolecular charge transfer property were designed and synthesized in this paper.The photophysical and photochemical properties were systematically studied,and their applications in dye sensitized photopolymerization,hydrogen abstraction photopolymerization,photo and thermal dual polymerization and two-photon initinated polymerization were explored.The research of this thesis mainly includes following parts:1.In this thesis,three series of acetylene bridged D-A type molecules were synthesized via Sonagashira coupling reaction,in which the electron acceptor groups are diphenylsulfone,benzophenone and thioxanthone,and the electron donor groups are carbazole,phenothiazine and triphenylamine.The proposed D-A type molecules are:(1)alkynyl conjugated A-?-D-?-A type aromatic amine derivatives with diphenylsulfone as electron withdrawing group(DSOs),including C-DSO,P-DSO and T-DSO;(2)alkynyl conjugated D-?-A and A-?-D-?-A type aromatic amine derivatives with benzophenone as electron withdrawing group(BPs),including C-MBP,C-DBP,P-MBP,P-DBP,T-MBP and T-DBP;(3)The alkynyl conjugated D-?-A and A-?-D-?-A type aromatic amine derivatives with thioxanthone(TXs)as electron withdrawing group,include C-MTX,C-DTX,P-MTX,P-DTX,T-MTX and T-DTX.The synthesized compounds were characterized by 1H NMR,13C NMR,FT-IR and HRMS.2.Researches on the photophysical properties of the synthesized D-A type?-conjugated molecules showed that:(1)DSOs molecules showed good absorption properties at 300?450 nm,and strong fluorescence emission at 400?550 nm.Both the emission wavelength and the quantum yield showed the positive solvation effect.In addition,DSOs possessed good two photon absorption property at 720?850 nm.For example,the molar extinction coefficient of T-DSO is more than 40000 M-1·cm-1 at 400 nm,and the fluorescence quantum yield in toluene can reach 0.68.The fluorescence quantum yields of C-DSO in toluene,1,4-dioxane and tetrahydrofuran are more than 0.80.The two photon absorption cross sections of P-DSO at 720?850 nm were all greater than 200 GM,and up to 1059 GM at 720 nm;(2)The BPs had similar absorption properties with DSOs.Both the aromatic amine and benzophenone groups have influences on the fluorescence properties,thus resulted in complicated fluorescence properties.The fluorescence properties of C-MBP and C-DBP showed hybridizationt of benzophenone-like local excited states and the intramolecular charge transfer states.The fluorescence of other BPs mainly emitted from the intramolecular charge transfer state and showed a positive solvation effect.In addition,DBPs showed excellent two-photon absorption properties from 720 nm to 860 nm,and the maximum absorption cross sections of C-DBP,P-DBP and T-DBP are 810 GM,2008 GM and 1292 GM,respectively.(3)The thioxanthone group played important roles in the UV-vis absorption properties not only as electron withdrawing group,the also as chromophore.TXs showed poor fluorescence properties except that P-MTX and P-DTX emmitted strong fluorescence in non-polar solvents.(4)The synthesized D-A type ?-conjugated molecules had good intramolecular charge transfer ability.The photophysical properties of compounds such as absorption wavelength and emission wavelength mainly depended on the chromophores,and the molar extinction coefficient and fluorescence quantum yielde are determined by the degree of conjugation and the type of electron withdrawing group.3.The studies on photostability,steady state photolysis and fluorescence quenching revealed that the DSOs had good photostability.The C-MBP,C-DBP,C-MTX,C-DTX,T-MTX and T-DTX showed good hydrogen ion reactivity,while other BPs and TXs molecules had good photostability and the benzophenone or thioxanthone groups mainly underwent charge transfer process.All of the D-A type conjugated molecules underwent efficient photo-induced electron transfer reaction with diaryliodonium salt(ION),triarylsulfonium salt(SON)and benzoyl peroxide(BPO).The photo excited phenothiazine based D-A type conjugated underwent efficient photo-oxidation reaction when interaction with ION,SON and BPO.The steady-state photolysis rate and fluorescence quenching constant were mainly determined by the type of photochemical reaction that occured during the photo-induced electron transfer process.4.The D-A type conjugated molecules showed good sensitization abilities for ION,SON and BPO under 405 nm LED light source.(1)The phenothiazine based D-A type molecules can be photo-bleached in free radical photopolymerization and showed extradinnary sensitization ability for SON.(2)The sensitization ability of the proposed D-A type conjugated molecules mainly depends on the excited state that the sensitization process accured.For example,C-DSO is a singlet sensitizer,and C-DTX is a triplet sensitizer,while C-DBP acted both singlet sensitizer and triplet sensitizer,thus the sensitization ability for ION following the order of C-DTX>C-DBP>C-DSO.(3)The BPO based photoinitiating systems showed excellent photo induced thermal and photo dual polymerization initiating ability,and thus had potential appilcations in frontal polymerization and photopolymerization of resins with deep color.(4)C-MBP,C-DBP,C-MTX,and C-DTX showed good photoinitiation properties as hydrogen abstraction initiators.(5)Two photon initiated polymerization were carried out with P-DSO and T-DSO.The polymerization threshold was maily determined by the the two photon absorption cross sections.The two photon excited fluorescence process may compete with the generation of radical.The addition of ION did not showd obvious improvement for to polymerization threshold,however,the accuracy of polymerization would be reduced as the ION is beneficial to the diffusion of radicals.5.The photoinitiation mechanism of the proposed two-component initiation systems were studied by transient absorption spectroscopy,electrochemistry and electron paramagnetic resonance and spin trapping experiments.Transient absorption spectra revealed that C-DBP,C-DTX and T-DTX had strong triplet-triplet absorption properties,and the positive absorptions were ascribed to the typical absorptions of benzophenone and thioxanthone at triplet states.The positive transient absorptions of P-DBP and P-DTX were attributed to the triplet absorption of phenothiazine.Electron paramagnetic resonance-spin trapping experiments showed that the tolyl radical,benzoyloxy radical,and?-aminoalkyl radical were the active radicals in ION,BPO and TEA based two components initiator systems,respectively.