【作者】 袁茂森；

【导师】 方奇；

【作者基本信息】 山东大学 ， 材料学， 2008， 博士

【摘要】 本论文对新型有机光电功能材料进行探索，并对化合物结构与性质间的构效关系进行讨论。我们认识到，有机光电功能分子与其三方面的结构属性相关：（1）π共轭性；（2）电荷转移性；（3）对称性。因而提出如下材料设计总体思想：以氮硼为电子授受中心的，以碳骨架为π共轭体，以“氮（Ⅴ）-碳（Ⅳ）-硼（Ⅲ）”作为理想D-π-A单元，在此基础上组合和扩展各种电荷转移模式（例如偶级子，四级子，八级子）。三价有机硼基团由于硼的缺电子性，成为一个强拉电子基（受体），和π共轭体系连接后可以形成p-π共轭而实现电荷转移。与硼相反的是，三价有机胺由于氮的孤对电子而成为一个强的推电子基（给体）。三聚茚（truxene）和三聚咔唑（triindole）基团是具有C₃对称性的，碳骨架为主的π共轭体。上述基团或结构单元是我们材料设计的物质出发点。我们分别把拉电子的二米基硼（米基是mesityl的译名，mesityl=2,4,6-trimethylphenyl）和推电子的二苯胺基与三聚茚和三聚咔唑键合，并在结构明确的基础上适当扩大中心核的π共轭体系，由此合成了一系列新的光电功能分子，较为系统地研究了它们的线性和非线性光物理性质，探索了它们在有机发光，双光子吸收及上转换荧光，多功能荧光探针，有机场效应器件等方面的应用。主要结果如下：1．化合物的合成与表征首次合成了以下17个具有π-D_n、π-A_n、A₂-π-D、A-π-D₂、D₃-π-A₃等分子构型的光电功能化合物，其分子结构已通过¹H NMR、¹³C NMR、质谱、元素分析等得到证实。有些分子已通过X-ray单晶结构测定。它们在固态和普通溶剂中是稳定的。2．晶体结构的测定与电子结构的计算用X-ray CCD测得5个新化合物的晶体结构。化合物B3、N3、03、04的结构数据表明：三聚茚呈很好的平面性。由三聚茚的2，7，12-位三个点所构成等边三角形，功能化后的B3、N3的三角形边长要比功能化前03的边长增加，这是在基态二米基硼的拉电子作用和二苯胺基的推电子作用的结果。B3结构中的硼原子与三聚茚之间的B-C键长明显短于硼原子与米基之间的B-C键长，与硼原子相连的苯环表现出苯醌结构，这表明硼原子与三聚茚之间的p-π共轭作用。分别测了化合物N2O2在室温（295 K）和低温（120 K）的晶体结构，随着温度的降低，化合物的中心对称消失，手征性出现，晶体空间群由常温下的P2₁／n转变为P2₁。密度泛涵量化计算表明，化合物B3中硼原子上的电荷密度在LUMO和LUMO+1中的电子密度比在HOMO中的大一个数量级，这说明了显著的激发态电荷转移，其它含硼化合物也表现出同样的光激发电荷转移性质。从化合物B2N和BN2的分子轨道图可以看出，在激发态，发生了从N原子到B原子非常剧烈的电荷转移。3．线性光学性质：系统研究了所合成化合物的吸收和荧光性质。重点考察了功能化、侧链支数、对称性、共轭桥、取代位置，以及不同极性溶剂等对光学性质的影响。（1）三聚茚在其2，7，12-位分别被二苯胺基和二米基硼基功能化后，无论吸收还是荧光都比前体明显红移，且荧光增强现象十分显著，荧光量子产率达到未功能化三聚茚的4-5倍，这都是推拉基团导致八极多向电荷转移的结果。（2）π-A₃或π-D₃型分子B3或N3其中的一个给（受）基被受（给）基取代形成D-π-A₂或D₂-π-A型分子B2N或BN2时，最大吸收峰位几乎没有变化，荧光发射峰却红移了110nm。B2N和BN2具有非常大的溶剂变色效应，非常大的Stokes位移。（3）对三聚咔唑的合成进行了成功探索。三聚咔唑同三聚茚相比，具有更长波的吸收峰和荧光峰，说明它具有更好的π共轭性。被二米基硼基团功能化后，吸收和荧光峰位进一步红移，这是因为三聚咔唑本身是一个富电体系，同吸电子的二米基硼基团之间可以形成更有效的推拉型电荷转移结构。（4）用二米基硼基受体分别在三聚咔唑端基不同位置（2，7，12-和3，8，13-位）取代，分别得到D₃-π-A₃型分子p-N3B3和m-N3B3。它们的吸收光谱中表现出较大的差异，构型分析结果表明：p-N3B3进行了跨越咔唑的长程电荷转移，而m-N3B3的短程电荷转移局限于苯环对位。4．非线性光学性质：研究了目标光电功能化合物在THF溶液中用800 nm激光激发的双光子上转换荧光性质：（1）所合成的光功能分子都表现出一定的双光子吸收（TPA）与双光子上转换荧光（TPEF）性质。具有八极电荷转移模式的化合物表现TPA增强效应。B系列化合物比N系列化合物具有更大的TPA截面。（2）兼含给体和受体的D-π-A₂或D₂-π-A型化合物B2N和BN2，在同一条件下的单光子荧光强度要比单含给体或受体的π-A₃或π-D₃型化合物B3和N3弱许多，但B2N和BN2双光子荧光强度却比B3和N3大出许多倍，前者的TPA截面也比后者大出一个数量级。这主要来自于B2N和BN2的推拉型电荷转移的贡献。（3）N1、N2、N3增长共轭链后得到TN1、TN2、TN3，其TPA截面增加了两个数量级。（4）三聚咔唑化合物N3T3、m-N383和p-N383具有相对较大的TPA截面，尤其是p-N383，分子中具有推拉电子基团，且具有长程电荷转移方式，TPA截面达到了250 GM。5．含硼化合物作为多功能荧光探针的研究D-π-A₂和D₂-π-A型化合物B2N和BN2在非质子溶剂中表现出大的荧光溶致变色效应，同时它们的斯托克斯位移△v_st和非质子溶剂取向极化率△f表现出了很好的线性关系，并对质子环境表现出与一般的极性探针不同的响应特性。这使其可以成为一种特异的环境极性荧光探针。本论文中所合成的含硼化合物无论在吸收还是荧光发射都对氟离子有灵敏响应和优良的选择性，可以用作氟离子探针来指示氟离子，尤其是化合物B2N和BN2，它们对氟离子具有独特的turn-on-off荧光响应，不仅在探测氟离子时具有极大的方便性，而且可以使它们对氟离子的探测灵敏度提高两个数量级。更多还原

【Abstract】 The main contribution of this paper is at exploring the novel organic photoelectric functional materials and discussing the structure-property relationships. We recognized that organic photoelectric functional molecules are related to three structural characters: （1）π-conjugation property; （2） charge-shift property; （3） molecular symmetry. So we put forward the following idea to the designing of materials: Nitrogen and boron are used as the centers of donor and acceptor respectively, and carbon framework asπ-conjugation bridge to built the perfect "N（Ⅴ）-C（Ⅳ）-B（Ⅲ）" D-π-A units. Based on these units, we assemble and extend some kinds of charge-shift models （e. g. dipolar, quadrupolar and octupolar models）.Because of the electron deficient nature of boron, three-coordinate organic boron group is a strong acceptor, which can lead to significant charge-transfer due to p-πconjugation when conjugated with an adjacent organicπ-system. As a comparison, three-valence organic amine group acts as a typical donor because of the lone of electrons of N. Truxene and triindole areπ-conjugated C-frameworks which possess C₃ symmetry. The above groups and units are our scratch line of our synthesis and materials preparation.We designed and synthesized a serial of novel organic photoelectric functional molecules by connecting dimesitylboryl （-B（Mes）₂） acceptor and diphenylamine group donor to the terminal of truxene and triindole or properly extending theπconjugated system of truxene and triindole. Their linear and nonlinear optical properties have been investigated in detail. We mainly explored their applications in organic light emitting, two-photon absorption （TPA）, two-photon excited fluorescence （TPEF） and multifunctional fluorescent probe.1. Synthesis and characteristic of the new compoundsA total of seventeen organic photoelectric functional compounds with the kinds ofπ-D_n,π-A_n, A₂-π-D, A-π-D₂ and D₃-π-A₃ have been firstly synthesized. Their constituents and structures have been fully characterized by ¹H NMR, ¹³C NMR, MS and elemental analysis. Some molecular structures have been determined by single crystal X-ray CCD diffraction. All of these new compounds are stable in solid state and in common organic solvents in air. 2. Crystal structures and electronic structuresFive single crystals have been determined by X-ray CCD single crystal diffraction. The crystallographic data of compounds B3, N3, 03 and 04 show that the truxene moiety has excellent planar structure. Three para-C atoms （2-, 7-, 12-） of truxene form an equilateral triangle, and the edge lengths of the B3 and N3 triangle are longer than that of 3 and 4, which is the result of charge-transfer based on the electron-pull nature of B atom and electron-push nature of aniline N atom. In B3 crystal, the B-C bond length between B atom and truxene is shorter than that between B atom and mesityl. The benzenes of truxene which connecting to B atom exhibit benzoquinone-like structure. All the above data indicate that there is p-πconjugation between boron atom and the truxene.The crystal structure of N2O2 has been determined at room temperature and low temperature respectively. The phase transition from P2₁/n （295 K） to P2₁ （120 K） happens accompanying the loss of centro-symmetry and the appearing of chirality. A calculation of B3 by using the density functional theory （DFT） shows that the negative charge on any B atom in LUMO and LUMO+1 is one order of magnitude larger than that in HOMO. From the graphs of molecular orbitals of B2N and BN2, we recognized that substantial negative charge have been transferred from the donor center of N atom to the acceptor center of B atom to B in their low lying excited LUMO state.3. Linear optical properties:The influences of functioning, branching, symmetry, conjugated bridge, substituted position and solvent, et al. to linear optical properties have been investigated.（1） After truxene is substituted at 2, 7, 12-positions by dimesitylboryl （A） or diphenylamine group （D）, the absorption and fluorescence spectra of the functional molecules B3 and N3 exhibit obvious red-shift compared with their precursor. The fluorescent enhancement is very notable and the fluorescence quantum yields （Φ） are 4-5 times that of the precursor. This is the results of octupolar charge shift derived from pull or push groups.（2） When one acceptor or donor ofπ-A₃ molecule B3 orπ-D₃ molecule N3 is replaced by a donor or an acceptor, the D-π-A₂ or D₂-π-A molecule B2N or BN2 will be formed. The absorption peak positions of the two kinds of molecules are almost same, but the emitting peaks of the D-π-A₂ or D₂-π-A molecule have a 110 run red shift compared with those of B3 or N3. B2N and BN2 exhibit remarkable solvatochromism and large Stokes Shift.（3） We successfully synthesized several novel triindole compounds. The maximal absorption and fluorescence peaks of triindole are longer than that of truxene, which indicates that triindole has largerπconjugation or electronic delocalization. When functionalized by dimesitylboryl group, triindole compounds has much red-shifted maximal absorption and fluorescence peaks than that of corresponding truxene compound. It is because of the electronic rich property of the triindole and the pull-push structure of its acceptor substitute compounds, which facilitates the charge transfer.（4） By connecting dimesitylboryl to the different positions of triindole （2, 7,12- or 3, 8, 13-）, compounds p-N3B3 and m-N3B3 have been obtained. Their absorption spectra have obvious distinction, and the results of theoretical conformation analysis indicate that p-N3B3 carries out a long-distance charge transfer spanning carbazole unit. However, m-N3B3 carries out a short-distance charge transfer spanning benzene.5. Nonlinear optical propertiesWe investigated the TPEF （Two-photon Excited Fluorescence） properties of all title photoelectric functional compounds in THF with 800 ran laser exciting.（1） All title functional compounds exhibit TPA and TPEF properties. The compounds with octupolar charge-transfer character exhibit TPA "cooperative enhancement". B serials compounds have large TPA cross sections than that of N serials compounds.（2） The SPEF （Single Photon Excited Fluorescence） intensity of D-π-A₂ or D₂-π-A molecule （B2N or BN2） is weaker than that ofπ-D₃ orπ-A₃ molecule （N3 or B3）. However, the TPEF intensity of B2N or BN2 are much stronger than that ofπ-D₃ orπ-A₃ molecule, and the TPA cross sections of B2N or BN2 are one order of magnitude that of N3 or B3, which result from the contribution of pull-push charge transfer of B2N and BN2.（3） TN1, TN2 and TN3 can be obtained by extending theπ-conjugation of N1, N2 and N3. The TPA cross sectionsσof TN1, TN2 and TN3 are two orders of magnitude that of N1,N2 and N3.（4） Triindole compounds N3T3, m-N3B3 and p-N3B3 have larger TPA cross sections and p-N3B3 has the largest TPA cross section of 250 GM among others. This excellent TPA property can be attributed to its electronic donor and acceptor groups, to the excellent 7r-conjugate system, and to its long-distance charge transfer.6. Boron （Ⅲ） compounds as multifunctional fluorescent probesNot only the D-π-A₂ and D₂-π-A molecules B2N and BN2 behave strong solvatochromism in aprotic solvent, but also their Stokes shift△v_st and aprotic orientation polarizability△f exhibit good linear relationship. And they exhibit different responding characters to protic environment compared to normal polar probes. These make them can be used as a special environmental polar probes.Both absorption and fluorescence spectra of all boron （Ⅲ） compounds exhibit sensitive and selective probing ability to F". Especially, the characteristic color change of B2N and BN2 make their detecting of F- more convenient, more sensitive, and less subject to external factors. Furthermore, the "off-and-on" character of BN2 or B2N means that they can act as highly sensitive and selective sensors, and the sensitivity to F^-probe can be enhanced 2 orders of magnitude.更多还原