含有噻唑生色团的Y-型有机分子的二阶非线性光学性质

采用密度泛函理论(DFT)B3LYP/6-31G*方法优化了一系列含有噻唑生色团的Y-型有机杂环分子的几何构型, 在此基础上结合有限场(FF)方法和含时密度泛函理论(TD-DFT)对分子的非线性光学(NLO)活性和电子光谱进行计算分析. 结果表明, 这些分子具有A-π-D-π-A(A: 受体, D: 给体)结构, 分子基态偶极矩、极化率和二阶NLO系数(β)随支链共轭桥的增长及生色团共轭效应的增大而增大. 同时, 该系列有机杂环分子的二阶极化率总的有效值(βtot)与其前线分子轨道能级相关, 分子的前线分子轨道能级差越小, βtot值越大.     

阴离子自由基TCNQ-及其铜盐CuTCNQ非线性光学性质的理论研究

采用量子化学方法计算分析了阴离子自由基TCNQ-及其铜盐CuTCNQ单体、二聚体的非线性光学(NLO)性质.结果表明,将Cu+引入TCNQ-分子,极化率值减小,Cu+的位置不同对分子NLO系数的贡献不同;二聚体分子的极化率与其结合能相关,同时分子的几何构型影响二阶NLO系数.由前线分子轨道组成得到,电子在前线分子轨道间...     

以苯等芳香环桥联的1,3-二硫杂环戊二烯衍生物的NLO性质

采用密度泛函理论(DFT)B3LYP/6-31G*优化一系列以芳环为桥联基团,1,3-二硫杂环戊二烯为供电子基团,丙二氰为吸电子基团的D-π-A型分子的几何结构,在此基础上对分子的极化率和第一超极化率进行计算.结果分析表明,桥联苯环数的增加,供电子基团(—OCH3)的引入及共轭桥的增长对分子的几何构型影响很小,但能使分子的二阶非线性光学(NLO)系数增加,且分子的最大吸收波长发生红移.甲氧基的引入或共轭桥的增长,分子的前线分子轨道能级差减小,TD-DFT计算表明分子深层占有轨道与空轨道之间的电子跃迁对二阶NLO效应也有较明显贡献.     

13顶点金属碳硼烷结构和非线性光学性质的DFT研究

采用量子化学密度泛函理论(DFT)B3LYP/6-31G(d)方法,对4,1,6-MC2B10H1213顶点金属碳硼烷几何构型进行优化,结合有限场(FF)方法计算了它们的极化率和二阶非线性光学(NLO)系数.结果表明,十个13顶点金属碳硼烷分子中1a～6a的二阶NLO系数与其构型纵向扩张呈现相同的规律.分子的前线分子轨道能级差越小,其二阶NLO系数越大.对于不同自旋态的同种金属碳硼烷分子,其偶极矩值为高自旋态大于相应的低自旋态,极化率和二阶NLO系数与自旋多重度没有一致的对应规律,自旋多重度对NLO性质影响不大.     

二芳基氨(硼)-π-碳硼烷三元化合物的二阶非线性光学性质的理论研究

采用密度泛函理论(DFT)方法对二芳基氨(硼)-π-十二顶点碳硼烷三元化合物的结构及二阶非线性光学(NLO)性质进行计算.结果表明,化合物共轭桥长度及二芳基氨(硼)对化合物偶极矩的影响较小.随着分子共轭桥的增长,分子的电子空间范围R2增大,从而使极化率和第一超极化率增大.通过分析化合物的电子光谱和对应的分子轨道组成可知,分子中电荷转移主要发生在二芳基氨(硼)和π-桥之间,碳硼烷的贡献较少.二芳基氨和二芳基硼的供电子能力差异可以调节分子的二阶NLO响应.     

新型苯并噻二唑衍生物的非线性光学性质理论研究

以苯并噻二唑分子为母体,设计了5个系列的衍生物,采用AM1半经验量子化学方法,研究了共轭π桥的不同增长方式和不同推拉电子基团对分子的电子结构及非线性光学性质的影响.结果表明:共轭链较短时,分子的二阶极化率和三阶极化率与共轭链长的线性相关性较好;而当共轭链较长时,分子的二价极化率和三阶极化率随着共轭链的增长而呈起伏性变化;与三氰基呋喃相比,三硝基呋喃对非线性极化率的影响更大;部分目标分子的一阶极化率α与Δμ·ΔE-1、二阶极化率β与α·ΔE-1、三阶极化率γ与α·ΔE-2和β·ΔE-1都有较好的相关性.     

双噻唑苯二聚体自由基分子的极化率与二阶超极化率的理论研究

采用量子化学UMP2/6-31G(d,p)方法优化双噻唑苯二聚体自由基分子的几何结构,以0.05nm为单位步长拉长与缩短2分子片之间的距离,选取5个点,采用DFTUB3LYP/6-31G(d,p)方法,对双噻唑苯二聚体自由基分子的极化率和二阶超极化率进行理论计算.结果表明,自由基体系的单重态为相对稳定状态.在完全重叠的体系中,在单、三重态时极化率都随着2分子片间距离的增大而增加;三重态时二阶超极化率的绝对值随着2分子片间距离的增大而增大.部分重叠的体系,单重态时极化率随2分子片距离的增大而减小;三重态时,二阶超极化率的绝对值随着2分子片间距离的增大而增大.     

含水杨醛缩苯胺双Schiff碱和吡啶配体的Zn(Ⅱ)配合物的电子结构和二阶非线性光学性质

以实验测定的晶体结构为基础, 用密度泛函理论的B3LYP方法, 在6-31G(d)基组水平上计算4个水杨醛缩苯胺类双Schiff碱和吡啶为配体的Zn(Ⅱ)配合物的电子结构, 并结合有限场(FF)方法得到二阶NLO系数. 结果表明, 在4个五配位配合物中, 双Schiff碱配体的共轭性减弱, 在Schiff碱配体引入叔丁基以及连接双Schiff碱的桥对配合物的结构影响很小. 同时4个配合物的配键性质、原子电荷分布、前线分子轨道能级等方面具有相似性. 但引入叔丁基改变了配合物前线分子轨道组成, Zn—O配位键的极性有所加强, 从而使配合物的极化率和二阶NLO系数增加, 而连接两个Schiff碱的桥对配合物二阶NLO性质影响不大.     

12顶点碳硼烷Ni(Ⅱ)配合物二阶非线性光学性质的理论研究

采用密度泛函理论方法, 计算分析了系列12顶点碳硼烷Ni(Ⅱ)配合物的非线性光学(NLO)性质和电子光谱. 结果表明, 2个P(CH₃)₃配体的结构变化对配合物的原子间距离影响较小, Ni(Ⅱ)配合物的极化率随取代基共轭性和空间体积的增加而增大. 增强配合物的共轭性及改变P(CH₃)₃配体结构对二阶NLO系数有明显影响, 其中取代基为苯胺的配合物5b的第一超极化率总有效值(β_tot)最大. 分析配合物的电子光谱和相应的分子轨道组成可知, 配体内的电荷转移以及配体到金属的电荷转移对二阶NLO系数贡献较大.     

具有电子给-受体结构的二茂铁衍生物的分子二阶非线性极化率

本文采用电场诱导二次谐波(EFISH)方法对所合成的10个金属有机分子的二阶非线性极化率进行了测试。这10个化合物是具有电子给体-受体共轭结构的二茂铁衍生物, 它们的非线性极化率大多未见报道。本文系统地研究了分子的给体-受体强度、共轭长度、共轭体系及共平面性等结构因素与分子二阶非线性极化率的关系。     

Theory-guided design and synthesis of multichromophore dendrimers: an analysis of the electro-optic effect

Extensive experimental and theoretical study suggests that interchromophore electrostatic interactions are among the most severe impediments to the induction and stability of large electro-optic coefficients in electric-field-poled organic materials. In this report, multichromophore-containing dendritic materials have been investigated as a means to minimize unwanted attenuation of nonlinear optical (electro-optic) activity at high chromophore loading. The dendritic molecular architectures employed were designed to provide optimized molecular scaffolding for electric-field-induced molecular reorientation. Design parameters were based upon past experimental results in conjunction with statistical and quantum mechanical modeling. The electro-optic behavior of these materials was evaluated through experimental and theoretical analysis. Experimental data collected from the dendrimer structures depict a reasonably linear relationship between chromophore number density (N) and electro-optic activity (r(33)) demonstrating a deviation from the dipolar frustration that typically limits r(33) in conventional chromophore/polymer composite materials. The observed linear dependence holds at higher chromophore densities than those that have been found to be practical in systems of organic NLO chromophores dispersed in polymer hosts. Theoretical analysis of these results using Monte Carlo modeling reproduces the experimentally observed trends confirming linear dependence of electro-optic activity on N in the dendrimer materials. These results provide new insight into the ordering behavior of EO dendrimers and demonstrate that the frequently observed asymptotic dependence of electro-optic activity on chromophore number density may be overcome through rational design.     

Benzophenone and zinc(II) phthalocyanine dichromophores-labeled poly (aryl ether) dendrimer: synthesis,characterization and photoinduced energy transfer

A series of benzophenone chromospheres and zinc(II) phthalocyanine dichromophores labeled poly (aryl benzyl ether) dendrimer (G_n-DZnPc(BP)_8n, n = 1?2) were synthesized. Their structures were characterized by elemental analysis, ¹H NMR, IR, UV–vis and matrix-assisted laser desorption/ionization time-of-flight spectrometry (MALDI-TOF MS). Their photophysical properties were examined by steady-state and time-resolved fluorescence methods. Both the poly (aryl benzyl ether) dendrimer and BP terminal chromophores had a significant effect on photophysical properties of the zinc(II) phthalocyanine core. Time-resolved spectroscopic measurements indicated that the lifetime of benzophenone (donor) chromophore was longer than that of the zinc(II) phthalocyanine (acceptor). The fluorescence of the peripheral benzophenone chromophores was quenched by the phthalocyanine group attached to the focal point. All of these observations suggest that an intramolecular singlet energy transfer occurs in G_n-DZnPc(BP)_8n molecules. The light-harvesting abilities of these molecules increased with generations due to an increase in the number of benzophenone chromophores. The energy transfer efficiencies were ca. 0.49 and 0.68 for generations 1 and 2, respectively, and the rate constants of the singlet-singlet energy transfer were ca. 10⁸ s^?1. The rate constants changed inconspicuously with increase of dendron generations. The intramolecular singlet-singlet energy transfer is proposed to proceed mainly via a Förster-type interaction mechanism involving the dendrimer backbone as a scaffold to hold the peripheral benzophenone chromophores and the phthalocyanine core together. This dendrimer was an effective new energy transmission complex with high efficiency and could be used as a potential light-harvesting system.     

异代酯基枝状分子表面组装及结构转化机理的STM研究

利用扫描隧道显微技术(STM)研究了3种异代酯基Janus枝状分子(G₁G₂COOCH₃, G₀G₃COOCH₃, G₁G₃COOCH₃)在高定向裂解石墨(HOPG)表面的组装结构. 室温下, G₁G₂COOCH₃, G₀G₃COOCH₃和G₁G₃COOCH₃分别在表面形成有序、局部有序及无序结构. 将样品加热至60~80 ℃后, 表面无序结构可以转化为有序的二聚体密堆积结构. 实验结果表明, 随着枝状分子代数的增加, 分子之间及分子与基底之间作用力增强, 室温下分子组装行为更依赖于分子吸附动力学过程, 组装结构趋于无序化, 而加热可以增强枝状分子在表面的活动性, 调整分子的位置关系, 使表面无序结构转化为热力学稳定的有序二聚体密堆积组装结构.     

巴比妥酸系列衍生物第一超极化率的理论研究及分子设计

在ZINDO方法基础上,按完全态求和(SOS)公式编制程序并计算了第一超极化率β,研究了巴比妥酸系列衍生物分子的结构、光谱和第一超极化率β(-2ω,ω,ω),β(0,0,0).考察了给体、桥和受体的变化、D-π-A结构及D-A-D结构和D-A结构对β的影响,设计了一系列有实际应用价值的热稳定性好,具有优良非线性光学性质的分子     

Probing the interior of peptide amphiphile supramolecular aggregates

We present a study of the aqueous solvation within self-assembled structures formed from peptide amphiphiles. We have placed tryptophan and pyrene chromophores onto the peptide backbone to enable spectroscopic examinations of the interior of the resulting supramolecular objects. Self-assembly constrains the chromophores to a defined location within an aggregate, and they experience differing degrees of quencher penetration reflective of their depth within the nanostructure. Tryptophan fluorescence indicates that the interiors remain well-solvated, suggesting that the supramolecular aggregates maintain high degrees of free volume. The Stern-Volmer quenching constants and the fractional accessibility (of covalently bound pyrene) progressively increase as the chromophore is placed closer to the aggregate exterior. Furthermore, these aggregates encourage chromophore uptake from aqueous solution as evidenced by the solubilization of free pyrene chromophores. Our findings demonstrate that covalently bound fluorophores within an aggregate can interact with the external environment. Studies with small molecular probes indicate that these self-assembled architectures may represent viable vehicles to sequester hydrophobic, insoluble organic molecules (within the interior) and to present signaling protein epitopes to cells (on the periphery).     

Wavelength dependence of first molecular hyperpolarizability of a dendrimer in solution

The frequency dependence of the first molecular hyperpolarizability of a dendrimer incorporated with thiophene-stilbene based charge-transfer chromophores is investigated by using a nanosecond 1907 nm laser and a number of wavelengths ranging from 1160 to 1760 nm emitted from an optical parametric amplifier pumped by a 1 kHz 130 fs Ti:sapphire laser. The measured hyperpolarizabilities are compared with those calculated from the charge-transfer absorption spectrum involving a Kramers-Kronig transformation scheme. The Kramers-Kronig transformation analysis provides a satisfactory account of the dispersion of the first molecular hyperpolarizability over the entire excitation wavelength range measured. The Kramers-Kronig technique extends the Oudar-Chemla two-level model previously proposed for the first molecular hyperpolarizability and it can be used in the nonresonance as well as the resonance region where the Oudar-Chemla model fails. The Kramers-Kronig transformation scheme allows a consistent intrinsic hyperpolarizability beta(0) to be obtained from the measured beta(HRS) using different excitation wavelengths for the dendrimer. The comparison of beta(0) for the dendrimer, which contains three chromophores, with that of corresponding monomer chromophore suggests that the chromophores inside the dendrimer are independent. This gives the evidence of the site isolation effect of the dendrimer and substantiates the larger macroscopic optical nonlinearity recently obtained for the dendrimer.     

Theoretical Analysis on Magnetic Properties of Conjugated Organic Molecules Containing Borepin

Theoretical study about the magnetic properties of conjugated organic molecules containing borepin with π current density was carried out. 1-(2,4,6-Trimethylphenyl)borepin moiety is the center and other different groups are situated on the both β sides, which are named molecules 1-12 as theoretical model in order to establish the relationship between aromaticity and geometry variation of borepin. The optimized molecular structures of molecules 1-12 are almost keeping planar and the C2-C3 bond length of borepin turns longer from molecule 1 to molecule 12. Different borepin-annulated ring could change the conjugated effect of π-electron between borepin and these borepin-annulated rings. Moreover, the molecule presents antiaromaticity, in other words, the molecule became unstable when the C2-C3 bond length of borepin extended more than ca. 0.1417 nm. But the β position fragment and substituent groups of borepin are not affected in this case, they are still steady. However, the central borepin ring current is counteracted by symmetrical overlap of it with affiliated borepin-annulated ring current. Hence, the central borepin ring breaking would be liable to occur. These molecules have higher vertical ionization potentials(VIPs) and lower vertical electron affinities(VEAs), which suggests that these molecules could easily exist in anionic form.     

Three-dimensional solution NMR spectroscopy of complex structures and mixtures

This paper reviews the non-biological applications of three dimensional NMR (3D-NMR) spectroscopy methodologies for studying chemical structures in polymer science, dendrimer research, organometallic chemistry, organosilicon chemistry, and mixtures of small organic molecules. Four methodologies for solving chemical structure problems are described, where the appropriate method is determined by the presence or absence of a third X nucleus (in addition to (1)H and (13)C) with suitable NMR properties.     

Synthesis,characterization, and application of melamine‐based dendrimers supported on silica gel

Dendrimers based on melamine have been covalently attached to silica gel with convergent and divergent approaches. These approaches yield different products. Each step of the synthesis can be monitored with Fourier transform infrared spectroscopy, thermal gravimetric analysis, and X‐ray photoelectron spectroscopy. The organic molecules can be isolated by chemical etching the organosilica material with HF and then analyzed by mass spectrometry. The convergent approach, which relies on the solution‐phase synthesis of the dendrimer before its attachment onto silica gel, produces materials that are ～20% w/w organic regardless of the generation of the dendrimer used in the preparation of these composites and without apparent defects in the dendrimer structure. Materials prepared with the divergent approach show increasing percentages of organic material with each generation, but the dendrimers show structural defects including incomplete branching. In a survey of sequestration potential, materials obtained with the divergent approach removed more atrazine from solution than the more homogeneous materials obtained from the convergent approach. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 168–177, 2005