【作者】 Muhammad Shabbir；

【导师】 苏忠民；

【作者基本信息】 东北师范大学 ， 物理化学， 2010， 博士

【摘要】 硼、氮化合物广泛存在于自然界以及人工合成化合物中,含硼、氮原子的官能团的存在赋予这些化合物体系不同的物理和化学性质。含硼、氮原子的官能团参与的化学反应往往具有独特的化学反应类型,从而在制备合成药物、农用化学品、染料、生物分子以及非线性光学（NLO）材料等方面发挥着重要作用。在暂短的过去的十年里,人们已经成功地合成大量的具有高内禀性非线性光学响应的化合物体系,并且在材料科学领域得到了广泛应用,比如:光学通信、信号处理、数据储存、图像重构、逻辑技术、感应探测以及光学计算等。目前,已有大量关于通过各种常规方法设计合成非线性光学响应增强的非线性光学材料的文献报道,这些设计策略主要有增加分子的π共轭体系、使用电子给体-π共轭桥-电子受体（D-π-A）模型、应用键长交替理论、扭曲π电子体系、将配位金属引入有机化合物以及采用多分枝手段增加电荷转移途径的分子等等。然而分子间相互作用,尤其是原子或离子的电负性以及电正性,对分子第一超极化率的影响,目前尚未得到充分的研究与探讨。本论文以碱金属（Li,Na,K）和卤素（F,Cl,Br）原子/离子掺杂在酸性含硼、氮原子基团分子体系为研究对象,旨在通过深入探讨这些掺杂原子/离子与酸性硼、氮基团分子的相互作用本质以及它们的非线性光学响应性质,希望找到一种完全不同于传统方法且能够显著改善材料非线性光学性质的设计策略。本论文主要围绕以下四个方面开展研究:1.苯邻二甲酰亚胺是具有“开-闭”（On-Off）特性的感应分子,通过调节各卤素离子与苯邻二甲酰亚胺间相互用来调控非线性光学性质。采用密度泛函理论（DFT）探讨了化学感应分子,N-（2-Methyl-1,3-dioxo-indan-5-yl）-benzamide （1）,与各卤素离子（F—,Cl—和Br—）的分子间相互作用。系统地研究了感应阴离子的结合过程。发现色度以及荧光信号的产生是由于Fˉ的引入使感应分子的基态去质子化造成的。与其它卤素离子（Clˉ和Brˉ）相比,Fˉ与感应分子间的结合能要高出两倍。设计的具有高结合能及更长波长吸收谱的体系1的系列衍生物,除化合物分子4-Methyl-N-（2-methyl-1,3-dioxo-indan-5-yl）- benzamide （2）外,均较母体化合物1有更好的感应灵敏度。2.理论设计了一系列具有可逆转换和调制的非线性光学（NLO）性质的新型分子化合物。采用密度泛函理论计算了四个dibenzoborole衍生物的静态第一超极化率（β）。结果表明,Fˉ的结合或单电子还原使dibenzoborole衍生物的β值明显增大。例如5-fluoro-5-（2,4,6-triisopropylphenyl）-2,8-dimethoxy-3,7-bithienyl-5H-di-benzo[d,b] borole ion （3·Fˉ）和5-fluoro-5-phenyl-3,7-bis-dinitrothienyl-5H-di-benzo[d,b]bor- ole ion （4·Fˉ）的β值分别增加至64×10^-30 esu和272×10^-30 esu,分别是母体5-（2,4,6-triisopropylphenyl）-2,8-dimethoxy-3,7-bithienyl-5H-dibenzo[d,b]borole （3）和5-phenyl-3,7-bis-dinitrothienyl-5H-dibenzo[d,b]borole （4） （无Fˉ）的12倍和4倍。同时单电子还原体系3Red和4Red也显示出相应中性体系化合物的47倍和15倍的β值。有趣的是,这类NLO转换具有二维特性。即大的远对角线超极化率张量与垂直分子偶极对称轴极化的电荷跃迁相关。态密度（DOS）和前线分子轨道（FMOs）分析表明,Fˉ结合于硼原子以及单电子还原过程破坏了硼原子的LUMOs中空的p轨道的Pz→π*共轭,从而导致了更大程度的垂直电荷跃迁和更大的β值的产生。该研究为该系列dibenzoborole化合物分子的多功能应用提出了新思路和新方法。尤其是对于已经被合成出来的具有高笛卡尔非线性各向异性（η= 10.48）的3·Fˉ分子来说,它能够在二维NLO分子转换开关中得到很好的应用。3.用氟离子以及酸性氢原子质子提取对不同苯并咪唑发色团NLO性质的调节研究。通过质子化/去质子化过程实现了一系列新型分子化合物的可逆二阶非线性光学转换和调节。密度泛函理论计算结果得出这种NLO转换可以实现第一超极化率（β0）从低至14×10^-30 esu （关闭状态）到高达1014×10^-30 esu （打开状态）的转换。在有效取代衍生物1^ˉ（1a^ˉ, 1b^ˉ, 1c^ˉ和1d^ˉ）中β0可被提升到2028×10^-30 esu。有趣的是,这些取代基化合物分子与它们相应的中性分子体系相比,其关-开NLO转换响应分别高出7、63、85和75倍。TD-DFT计算以及自然键轨道（NBO）、前线分子轨道和分子静电势（MEP）分析结果表明,酰亚胺的质子提取使得到的阴离子分子构型转换为推-拉构型,致使吸收和发射光谱发生红移,进而表现为高的二阶NLO分子转换响应。该类发色团分子的Fˉ复合物显示出类似的NLO转换性质,也具有较高的β₀值和与去质子化阴离子复合物类似的光学性质。并且气相酸度（GPA）计算表明中性分子化合物1及其衍生物（1a, 1b, 1c, and 1d）分子具有典型的氮酸特性,很容易被解离为稳定的去质子化阴离子物种。4.研究了多面体硼烷、碳硼烷以及硼烷衍生物与不同碱金属的相互作用及其对非线性光学性质的调控作用。采用量子力学方法设计了含有篮子构型十氢硼烷(B₁₀H₁₄)配体的新型锂十氢硼烷(Li@B₁₀H₁₄)复合物。Li原子以句柄式封端结合于十氢硼烷篮子的亲电硼原子,其NBO电荷q （Li）为0.876,接近+1.这表明Li原子被离子化形成阳离子并且在B₁₀H₁₄的开口端形成一个阴离子区域。最有趣的是这种掺杂的Li具有松散的价电子构型,并且被拉向B₁₀H₁₄篮子的中心空位,在B₁₀H₁₄篮子开口端的缺电子性质作用下形成离散的电子构型。很明显,Li@B₁₀H₁₄的第一超极化率（β0）高出B₁₀H₁₄近340倍,分别为23075 au (199×10^-30 esu)和68 au。此外,B₁₀H₁₄篮子中Li的插入导致其Raman光谱、¹¹B NMR和紫外可见光谱随其电子结构的变化而显现出新的特征峰,这使实验工作者能够很容易表征这种新型的Li@B₁₀H₁₄复合物。该研究结果很可能带动一些新兴研究领域的发展,譬如碱金属-硼烷体系在NLO方面的应用。5.进一步地,对一系列篮形体系B₁₀H₁₄和Li@B₁₀H₁₄的氟衍生物的非线性光学响应和热稳定性进行了系统的理论研究。结果显示,在推电子和拉电子的双重效应作用下,Li@6,9-F₂B₁₀H₁₂,Li@1,3,6,9-F₄B₁₀H₁₀和Li@2,4,6,9-F4B₁₀H₁₀不仅具有非常大的第一超极化率（β0）值181124,133199和32314 au,而且垂直电离势（VIP）较大,分别为6.447,6.302和6.885 eV。与已报道的体系相比,当前体系的第一超极化率和垂直电离势都明显大于Li原子掺杂氟碳链（J. Am. Chem. Soc. 2007,129,2967）以及我们设计的Li@ B₁₀H₁₄篮形体系（J. Am. Chem. Soc. 2009,131,11833）的值。此外,我们首次利用在298 K时的锂化和氟化反应焓（Δ_rH^o）探讨体系的热稳定性。对于B₁₀H₁₄ , 6,9-F2B10H12和2,4-F2B10H12锂化反应焓分别是-10.04 , -11.29和-13.18 Kcal/mol,这显示了B₁₀H₁₄的氟衍生物与锂原子反应的机率较高。所得结果不仅解释了氟原子的数量和位置对于B₁₀H₁₄,Li@B₁₀H₁₄的影响,而且结合推电子和拉电子两个效应产生更弥散的额外电子,使B₁₀H₁₄和Li@B₁₀H₁₄的氟衍生物具有大的非线性光学响应和高的热稳定性。更多还原

【Abstract】 Functional groups containing nitrogen and boron atoms are present in a variety of naturally occurring and man made compounds. These functional groups impart different physical and chemical characteristics to these compounds. These groups are responsible for their unique chemical reactivity patterns and play crucial roles in the preparation of drugs, agrochemicals, dyes and molecules of life and nonlinear optical （NLO） materials and so on. There has been considerable success in the past decade at preparing compounds with large intrinsic nonlinear optical properties. Materials exhibiting NLO response are currently of great scientific and technological interest for applications as diverse as optical telecommunications, signal processing, data storage, image reconstruction, logic technologies, sensor protection, and optical computing. A large number of reports have been presented up till now on NLO materials with different conventional strategies to enhance NLO response. These strategies mainly include the use of the molecules with the extendedπ-electron systems, planer donor-πconjugated bridge-acceptor （D-π-A） model, bond length alternation （BLA） theory, twistedπ-electron systems, incorporation of ligated metal into the organic compounds, multi branches molecules with inceasing ability the charge transfer, and so forth. However, the intermolecular interaction effect of electronegative and electropositive atoms/ions on different acidic molecules containing nitrogen and boron atoms has not been studied from electro-optical point of view.In this thesis, we have selected first three alkali metals i.e. Li, Na, K and three halogens i.e. F, Cl, Br atoms/ions to dope them with different acidic molecules containing nitrogen and boron atoms. The interactions of these atoms/ions with different acidic molecules containing nitrogen and boron and their effects on the NLO properties of these molecules were investigated to find out a strategy, which is different from the above stated conventional methods for the improvement of significantly large NLO response. Our work will focus on the four different aspects in this regard:1. The effect of intermolecular interaction of a phthalimide based“On-Off”sensor with different halides ions （F）: Tuning its efficiency and electro- optical properties The interaction between chemosensor, N-（2-Methyl-1,3-dioxo-indan-5-yl）-benzamide （1） and different halides ions （Fˉ, Clˉand Brˉ） has been investigated using density functional theory （DFT）. A clear insight of the sensor anion binding process has been presented. Our calculations revealed that the observed colorimetric and fluorescent signals are induced due to the ground state deprotonation of the sensor molecule caused by Fˉwhich has two times higher binding affinity than other halide ions （Clˉand Brˉ）. Derivatives of system 1 have been made to find a better sensor with higher binding affinity and longer wavelength of absorption. All the derivatives are better sensors than the parent 1 except 4-Methyl-N-（2-methyl-1,3-dioxo-indan-5-yl）- benzamide （2）.2. In our second report, a new sequence has been presented for the reversible switching and modulation of NLO. The static first hyperpolarizabilities （β） of four dibenzoborole derivatives have been computed by DFT. Theβvalues of these dibenzoborole derivatives have shown a significant increase with the attachment of Fˉand/or one electron reduction. For example, 5-fluoro-5-（2,4,6-triisopropylphenyl）-2,8-dimethoxy-3,7-bithienyl-5H-di-benzo[d,b] borole ion （3·F^ˉ） and 5-fluoro-5-phenyl-3,7-bis-dinitrothienyl-5H-di-benzo[d,b]borole ion （4·F^ˉ） both showedβvalues as large as 64×10^-30 esu and 272×10^-30 esu, that is about 12 times and 4 times larger than their counterparts 5-（2,4,6-triisopropylphenyl）-2,8-dimethoxy-3,7-bithienyl-5H-dibenzo[d,b]borole （3） and 5-phenyl-3,7-bis-dinitrothienyl-5H-dibenzo[d,b]borole （4） （without F^ˉ） respectively. Similarly, systems 3Red and 4Red （one electron reduced） also showed 47 times and 15 times largerβvalues than their neutral forms respectively. Interestingly, this NLO switching is two dimensional in characteristics, in which large off-diagonal hyperpolarizability tensors can be related to the charge-transfer transitions which are polarized perpendicular to the molecular dipolar axis. Density of states （DOS） and frontier molecular orbital （FMO） analysis show that the binding of F^ˉat a boron atom and/or one electron reduction process turn off the Pz→π*conjugation of vacant p-orbital of boron atom in LUMOs, resulting in a higher extent of perpendicular charge transfer （CT） and lagerβvalues. The present investigation reveals a new idea and different means for multifunctional use of the present dibenzoborole class, especially （already synthesized） 3·F^ˉas two-dimensional NLO molecular switch with cartesian nonlinear anisotropy as large asη= 10.48.3. Different benzimidazole chromophores have been studied to tune their NLO properties with fluoride ions and on proton abstraction from acidic hydrogen atom. A novel sequence for reversible second-order NLO molecular switching with protonation/deprotonation has been achieved and tuned as well. The NLO switching with first hyperpolarizabilities （β₀） as low as 14×10^-30 esu （Off-phase） and as large as 1014×10^-30 esu （On-phase） have been computed by using the density functional theory （DFT）. Thisβ₀ value has been tuned up to 2028×10^-30 esu by effective substitutions in the derivatives of 1^ˉ（1a^ˉ, 1b^ˉ, 1c^ˉ, and 1d^ˉ）. Interestingly, the substituted compounds have illustrated robustly large off-on NLO switching with the difference ofβ0 values as 7, 63, 85 and 75 times larger than their neutral counterparts, respectively. TD-DFT calculations along with natural bond orbital （NBO）, frontier molecular orbitals （FMOs） and molecular electrostatic potential （MEP） analyses depict that the abstraction of imido proton reverts the push-pull configurations resulting in a red shift for both absorption and emission spectra which leads to a high performance second-order NLO molecular switching. A similar trend of NLO switching in Fˉcompounds of these chromophores has also been observed with significantly largeβ0 values having analogous electro-optical properties like deprotonated anions. Furthermore, gas-phase acidity （GPA） calculations for the neutral molecule 1 and its derivatives （1a, 1b, 1c, and 1d） have also revealed that these are rationally potent nitrogen acids and can easily be dissociated to produce stable deprotonated anions.4. Polyhedral boranes, carboranes and borane derivatives have been used to study their interaction with different alkali metals. An innovative type of lithium decahydroborate (Li@B₁₀H₁₄) complex with a basket like complexant of decaborane (B₁₀H₁₄) has been designed using quantum mechanical methods. As Li atom binds in a handle fashion to terminal electrophilic boron atoms of decaborane basket, its NBO charge q （Li） is found to be 0.876, close to +1. This shows that the Li atom has been ionized to form a cation and an anion at the open end of B₁₀H₁₄. The most fascinating feature of this Li doping is its loosely bound valence electron, which has been pulled into the cavity of B₁₀H₁₄ basket and become diffuse by the electron deficient morphological features of the open end of B₁₀H₁₄ basket. Strikingly, the first hyperpolarizability （β0） of Li@B₁₀H₁₄ is about 340 times larger than B₁₀H₁₄, computed to be 23075 au (199×10^-30 esu) and 68 au respectively. Besides this, the intercalation of Li atom to the B₁₀H₁₄ basket brings some distinctive changes in its Raman, 11B NMR and UV-Visible spectra along with its other electronic properties that might be used by the experimentalists to identify this novel kind of Li@B₁₀H₁₄ complex with large electro-optical response. This report may evoke the possibility to explore a new thriving area i.e. alkali metal-boranes for NLO application.5. Fluoro derivatives of B₁₀H₁₄ and Li@B₁₀H₁₄ baskets have been designed to achieve robustly large NLO response and thermal stability under simultaneous effects of conical-push and inward-pull, which have been reported discretely in previous lithium NLO complexes. Among the various derivatives, Li@6,9-F2B10H12, Li@1,3,6,9-F4B10H10 and Li@2,4,6,9-F4B10H10 have shown first hyperpolarizability （β0） values as large as 181124, 133199 and 32314 au along with vertical ionization potentials （VIPs） of 6.447, 6.302, 6.885 eV, respectively. The first hyperpolarizability values and VIPs are significantly larger than previously reported Li-doped fluorocarbon chains at the same MP2/6-31+G* level of theory （J.Am.Chem.Soc. 2007, 129, 2967）. These values also exceed from our formerly designed Li@B₁₀H₁₄ basket （J.Am.Chem.Soc. 2009, 131, 11833）. Further, the enthalpies of lithiation and fluorination reactions （Δ_rH^o） at 298 K are obtained to explore the thermal stability for the first time. The calculated enthalpies of lithiation reactions are -10.04, -11.29 and -13.18 Kcal/mol for B₁₀H₁₄, 6,9-F2B10H12, and 2,4-F2B10H12 respectively which demonstrate a higher probability of fluoro decaboranes for reaction with lithium. The obtained results not only explain the effect of positions and number dependence of substituted fluoro atom（s） in B₁₀H₁₄ and Li@B₁₀H₁₄ but also elucidate a unification of previous two benchmark strategies which have been used independently to polarize lithium excess electron for high NLO response and thermal stability.更多还原