氰基取代的螺芴氧杂蒽衍生物:激基复合物发光与性质调控

热活化延迟荧光分子因具有高效发光、价格低廉等优点,在发展有机发光二极管方面显示出巨大潜力.与单分子相比,激基复合物容易实现小的单线态-三线态能隙差,在开发延迟荧光材料方面备受关注.然而,相应受体材料的种类仍较为稀少,且激基复合物延迟荧光性质与受体材料结构之间的关系还需深入探讨.本工作设计合成出两个新型的基于螺芴氧杂蒽的电子受体材料（CNSFDBX和DCNSFDBX）.结果表明,它们与给体材料TCTA掺杂后均呈现激基复合物发射,其中TCTA：DCNSFDBX掺杂体系显示更高的发光效率,其原因归结为双氰基取代使得DCNSFDBX具有更强的接收电子的能力.该工作为开发新型电子受体材料用于激基复合物延迟荧光提供了思路.     

三发色基团体系分子内激基复合物形成的环境效应

芳香烃的荧光可以被电子给体如叔胺化合物淬灭,这一现象早为人们所熟知.随着芳烃分子荧光的淬灭出现一个向红移无结构的新荧光峰,它被认为是激发态芳香烃分子A与电子给体D相互作用形成的激基复合物(exciplex)DA所发射的荧光.将两个、三个或更多个发色基团用非共轭链连接起来,受光激发后则可以形成分子内激基复合物.通过这些体系我们可以研究电子给体和电子受体相互作用的机制,研究在复杂的氧化、还原体系(如光合作用)     

咔唑及其衍生物对 9-氰基蒽的荧光猝灭机理的研究

本文研究咔唑及其衍生物对9-氰基蒽(9CNA)的荧光猝灭机理。结果表明, 猝灭过程有以下三种方式:(1)一系列N-烷基咔唑及1,4-二咔唑丁烷、反式1,2-二咔唑环丁烷、N-苄基咔唑等对9CNA的荧光猝灭是通过形成激基复合物。(2)咔唑对9CNA的荧光猝灭是通过形成氢键。(3)1,3-二咔唑丙烷及N-痖烯基咔唑对9CNA的荧光猝灭是属于一般碰撞猝灭过程。以上所有猝灭过程主要都是来自电荷转移相互作用。另外, 还讨论了空间位阻对形成激基复合物的影响。并由稳态和动态荧光实验结果,应用Ware关于激基复合物的形成和解离的动力学公式计算出一系列光物理速率常数。     

咔唑与N-烷基咔唑光物理行为的差异

已知甲基、乙基咔唑等咔唑的衍生物与对位苯二甲酸二甲酯(DMTP)和邻位苯二甲酸二甲酯(DMP)可以形成激基复合物^[1],但是咔唑与DMTP或DMP相互作用时观察不到激基复合物的荧光。     

基于氰基化9-苯基芴衍生物的激基复合物发光与性质研究

激基复合物发光器件因给、受体材料掺杂比例易调且易实现小的单线态-三线态能隙差等优势, 在发展工艺简单、性能高效的有机发光二极管方面显示出很大的应用潜力. 针对目前激基复合物受体材料的种类仍较为匮乏, 器件性能仍需改善等问题, 本工作设计合成出新型基于9-苯基芴的电子受体材料(TCNDPFCz)用于构筑激基复合物发光器件. 实验表明, 受体分子TCNDPFCz与给体分子1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC)掺杂后(TAPC: TCNDPFCz)呈现明显的激基复合物发光, 其光致发光效率为54%, 电流效率为27.2 cd•A^‒1, 功率效率为32.9 lm•W^‒1, 外量子效率为12.5%. 经分析, 我们推测激基复合物TAPC:TCNDPFCz形成的过程得益于TCNDPFCz具有很强的吸电子能力. 本工作表明9-苯基芴可以作为骨架单元来构筑受体分子, 为开发新型电子受体材料提供了新策略.     

N-乙烯基咔唑的光聚合

N-乙烯基咔唑的三氯甲烷溶液经光照后可以获得聚N-乙烯基咔唑,这一结论已经通过荧光光谱和NMR谱得到证实,产率很高可达70％。又通过荧光淬灭实验证实:这一反应首先在光照下形成激基复合物,由激基复合物分解产生自由基而引发N-乙烯基咔唑的聚合,此外,本文还研究了光强、N-乙烯基咔唑的浓度和光照时间对产率的影响。     

痂囊腔菌素A与咔唑化合物间的光致电子转移

研究了咔唑、咔唑-9-乙酸、3-溴-咔唑-9-乙酸在缺氧条件下对天然苝醌化合物痂囊腔菌素A(简记为EA)的荧光猝灭行为;由竹红菌甲素(HA)和乙素(HB)的荧光寿命估算了EA在乙腈中的荧光寿命,并进而计算了三个咔唑化合物的双分子猝灭速度常数.结果表明,三个咔唑化合物在EA的可见光吸收区无光吸收,据此推测其对EA的荧光猝灭作用归因于咔唑化合物作为电子给体而EA作为电子受体的光致电子转移作用.三个咔唑化合物的Stern-Volmer猝灭常数分别为698、704和1 063L·mol-1;乙酸基对咔唑环的光致电子转移速率几乎没有影响,而溴原子取代能够增加咔唑化合物对EA的荧光猝灭程度和光致电子转移速率.此外,EA在乙腈中的荧光寿命为1.98ns,而三个咔唑化合物的双分子猝灭速率常数分别为3.52×1011,3.56×1011和5.37×1011 L·mol-1·s-1.     

2-(ω-联苯基多亚甲基)-5-联苯基-1,3,4-二唑的荧光光谱研究

本文测定了双荧光团化合物2-(ω-联苯基多亚甲基)-5-联苯基-1,3,4-二唑及其模型化合物2-甲基-5-联苯基-1,3,4-二唑和2,5-二联苯基-1,3,4-二唑的荧光光谱.对分子内,分子间激基缔合物和激基复合物的形成进行了研究,并对分子构型与形成分子内激基复合物之间关系作了初步探讨.从实验结果得到,亚甲基桥链的碳数为奇数时容易形成分子内激基复合物.     

同分异构体对形成激基复合物的影响——对位和邻位苯二甲酸二甲酯与乙基咔唑形成的激基复合物

对位和邻位苯二甲酸二甲酯与乙基咔唑都能形成激基复合物,但对位苯二甲酸二甲酯对乙基咔唑荧光的淬灭常数大于邻位苯二甲酸二甲酯对乙基咔唑的淬灭常数,所形成的激基复合物的荧光谱带的峰位置也不一样,前者的峰位置的波长较短,它们形成激基复合物的速度常数K_3和分解为原初状态的速度常数K_4也都不一样,对位的两个速度常数分别大于邻位的两个速度常数,这些实验结果无法用已有的理论进行统一的解释,因此我们假定了一个新的模型,这一模型可以满意地解释现有的实验结果。     

上转换荧光化合物DMSSB与CSSB的合成、结构与光物理性质

以苯并噻唑为电子受体,以双苯乙烯基为共轭桥链,分别以二甲基胺和咔唑为电子给体合成了2个新的有机化合物DMSSB(反式,反式-2-{4-[(4-N,N-二甲基胺)苯乙烯基]苯乙烯基}-1,3-苯并噻唑)和CSSB(反式,反式-2-{4-[(4-N-咔唑)苯乙烯基]苯乙烯基}-1,3-苯并噻唑).用X射线衍射方法测定了CSSB的晶体结构.用波长为800nm的激光激发时,DMSSB与CSSB在THF中分别发出强的上转换橙色(λ_max=589nm)和蓝绿色荧光(λ_max=488nm).2个化合物在不同溶剂中的光物理数据和理论计算结果表明,苯并噻唑基是一个很好的电子受体.     

Magnetic field effect on fluorescence in a mixture of N-ethylcarbazole and dimethyl terephthalate in a polymer film in the presence of electric fields

Magnetic field effects on the fluorescence spectrum and on the electrofluorescence spectrum (plots of the electric field-induced change in fluorescence intensity as a function of wavelength) have been examined in electron donor and acceptor pairs of N-ethylcarbazole (ECZ) and dimethyl terephthalate (DMTP) in polymer films at different ratios of donor/acceptor concentration. In the mixture having a high concentration of ECZ, electric field-induced quenching of the exciplex fluorescence originating from the photoinduced electron transfer becomes less efficient in the presence of a magnetic field. In the mixture having a low concentration of ECZ, on the other hand, no magnetic field effect was observed in the electrofluorescence spectrum, indicating that the hole carrier plays an important role in synergy effects of magnetic and electric field effects on exciplex fluorescence. In the absence of the applied electric field, the magnetic field does not affect either exciplex fluorescence with a peak at 450 nm or LE fluorescence emitted from the locally excited state of ECZ but enhances the broad emission with a peak at approximately 380 nm, probably assigned to the fluorescence of another type of exciplex between ECZ and DMTP. Thus, two kinds of magnetic field effects on fluorescence have been observed in a mixture of ECZ and DMTP in a polymer film.     

以芳香硫醚为桥链的三体化合物的荧光分子开关性能

将一些发色团分子组装成具有特定功能的分子器件,是近年来随超分子化学和分子信息科学兴起而十分活跃的领域［１］,其中具有逻辑功能的光控开关器件是下一代分子计算机的核心,它们可在分子水平实现信息的存储和数据的处理、传输［２］．国内外这方面的研究主要有顺反异...     

Long range energy transfer in conjugated polymer sequential bilayers

Steady-state and time-resolved photoluminescence have been used to investigate the optical properties of bilayer and blend films made from poly(9,9-dioctyl-fluorene-2,7-diyl) (PFO) and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH PPV). Energy transfer has been observed in both systems. From steady-state photoluminescence measurements, the energy transfer was characterized by the effective enhancement of the MEH PPV emission intensity after exciting the donor states. Relatively faster decays for the PFO donor emission have been observed in the blends as well as in the bilayer structures, confirming effective energy transfer in both structures. In contrast to the bilayers, the time decay of the acceptor emission in the blends presents a long decay component, which was assigned to the exciplex formation in these samples. For the blends the acceptor emission is in fact a composition of exciplex and MEH PPV emissions, the later being due to Fo?rster energy transfer from PFO. In the bilayers, the exciplex is not observed and temperature dependence photoluminescence measurements show that exciton migration has no significant contribution to the energy transfer. The efficiency and very long range of the energy transfer in the bilayers is explained assuming a surface-surface interaction geometry where the donor/acceptor distances involved are much longer than the common Fo?rster radius.     

Luminescence studies in polymers—VII. Exciplex formation in polyvinylnaphthalene and polyacenaphthylene

The reactivities of polymers in exciplexes and CT complex formation were compared with those of model compounds for the following systems in solution: (1) exciplexes between excited diethylaniline as donor and ethylnaphthalene, acenaphthylene, poly-1-vinylnaphthalene or polyacenaphthylene; (2) exciplexes between excited dicyanoanthracene as acceptor and the same aromatics as donors: (3) CT complexes between chloranil and either poly-1-vinylnaphthalene or polyacenaphthylene. The rate constant for exciplex formation was found to be much larger for the model than for the polymer when diethylaniline is the donor and poly-1-vinylnaphthalene or ethylnaphthalene the acceptor. The equilibrium constant for CT complex formation between chloranil and the same aromatics is also higher in the case of model compounds. This difference is tentatively assigned to entropy terms arising from the lower accessibility of the aromatic groups fixed on a polymer backbone. These conclusions are extended to the other systems. Exciplexes do not form in poly-1-vinylnaphthalene or polyacenaphthylene films containing dicyanoanthracene.     

Determination of the barrier to intramolecular exciplex formation in a jet-cooled, bichromophoric molecule

The emissive properties of a bichromophor molecule (1) are reported. This contains an anilino group as an electron donor (D) and a 1-cyanonaphthalene group as an electron acceptor (A) interconnected by a saturated hydrocarbon bridge of limited flexibility, which holds D and A far apart in the electronic ground state. The emission spectrum of 1, both in solution and in the gas phase, indicates that quantitative formation of an intramolecular exciplex between D and A occurs. This exciplex formation was studied as a function of excitation energy in molecules of 1 isolated in a supersonic free jet. A barrier of 1700 ± 200 cm⁻¹ was found between the Franck-Condon excited conformation and the conformation of the exciplex. Although this value is significantly higher than that reported earlier for exciplex formation between chromophores connected by a simple polymethylene chain (≈ 900 cm⁻¹) it is much lower than the barrier predicted for folding the bridge in 1 sufficiently to bring D and A in close contact. A tentative explanation of this discrepancy is given.     

高分子链对激发态芳烃和胺相互作用的影响

本文研究了在激发状态下芳烃(受体)和脂肪胺(给体)的相互作用以及高分子链在其中的影响。结果表明,高分子胺与不带高分子链的胺相比,其对激发态芳烃的淬灭速度和形成激基复合物的能力都强得多,并且激基复合物光谱发生明显红移。     

Photoinduced intra- and intermolecular electron transfer in solutions and in solid organized molecular assemblies

The present paper highlights results of a systematic study of photoinduced electron transfer, where the fundamental aspects of the photochemistry occurring in solutions and in artificially or self-assembled molecular systems are combined and compared. In photochemical electron transfer (ET) reactions in solutions the electron donor, D, and acceptor, A, have to be or to diffuse to a short distance, which requires a high concentration of quencher molecules and/or long lifetimes of the excited donor or acceptor, which cannot always be arranged. The problem can partly be avoided by linking the donor and acceptor moieties covalently by a single bond, molecular chain or chains, or rigid bridge, forming D-A dyads. The covalent combination of porphyrin or phthalocyanine donors with an efficient electron acceptor, e.g. fullerene, has a two-fold effect on the electron transfer properties. Firstly, the electronic systems of the D-A pair result in a formation of an exciplex intermediate upon excitation both in solutions and in solid phases. The formation of the exciplex accelerates the ET rate, which was found to be as fast as >10(12) s(-1). Secondly, the total reorganization energy can be as small as 0.3 eV, even in polar solvents, which allows nanosecond lifetimes for the charge separated (CS) state. Molecular assemblies can form solid heterogeneous, but organized systems, e.g. molecular layers. This results in more complex charge separation and recombination dynamics. A distinct feature of the ET in organized assemblies is intermolecular interactions, which open a possibility for a charge migration both in the acceptor and in the donor layers, after the primary intramolecular exciplex formation and charge separation in the D-A dyad. The intramolecular ET is fast (35 ps) and efficient, but the formed interlayer CS states have lifetimes in microsecond or even second time domain. This is an important result considering possible applications.     

双枝芳醚树枝形聚合物构象研究

合成了外围只以一个芘基团修饰、核心为苯胺的双枝芳醚树枝形聚合物Py-[Gn]2-NPh (n＝1～2), 利用分子内电子转移和激基复合物的形成对其折叠构象和折叠程度进行了研究. 二氯甲烷溶液中选择性激发芘基团, 树枝形聚合物Py-[Gn]2-NPh分子内发生从苯胺到芘基团之间的电子转移, 观察到了分子内外围芘基团和核心苯胺基团之间形成激基复合物的发光, 为芳醚树枝形聚合物折叠构象的存在给出了直接实验观察. 二氯甲烷溶液中1～2代Py-[Gn]2-NPh分子内电子转移效率分别为0.87和0.81, 速率常数分别为2.3×108和1.5×108 s－1. 利用电子转移速率常数估算得到1～2代Py-[Gn]2-NPh分子内给、受体之间的距离分别为0.79和0.81 nm, 说明双枝芳醚树枝形聚合物与单枝结构类似, 其外围基团也可以折叠到达分子内部接近核心的位置.     

Exciplexes photonics on the silica surface

Processes of photoinduced electron transfer and formation of bimolecular complexes on the surface of nonporous dispersed silica and aerosil have been explored. Complexes of the two types, with a dissociative (acene + electron donor) and a stable (acene + acceptor) ground state have been obtained. Formation of the anthracene-N,N-diethylaniline exciplex on the surface proceeds in a diffusion mode. Increasing the quencher concentration to σ = 1% is accompanied by exciplex formation. Formation and stabilization of Mullican’s (dark) complexes has been noted with σ = 10%. The reaction of complexation on the surface is stimulated by heating. A suggestion of CTC localization in places of the highest energetic uniformity of the surface has been made.     

Magnetic field effect in fluorescence of excited fluorophore equilibrated with exciplex that reversibly dissociates into radical-ion pair undergoing the spin conversion

The fluorescence of the photoexcited electron acceptor, (1)A?, and the exciplex, (1)[D(+δ)A(-δ)] formed at contact of (1)A? with an electron donor (1)D, is known to be very sensitive to a magnetic field, assisting the spin conversion in the resulting geminate radical ion pair (RIP), (1, 3)[D(+)...A(-)]. The relative increase of the fluorescence in the highest magnetic field compared to the lowest one, known as the magnetic field effect, crucially depends on the dielectric constant of the solvent, ?. This phenomenon first studied experimentally is at first reproduced here theoretically by means of the so called integral encounter theory. It was shown to be very sensitive to the position of the exciplex energy level relative to the levels of exciplex precursors and the charged products of its dissociation. The results obtained strongly depend on the dielectric properties of the solvents as well as on the exciplex and RIP formation rates.