过渡金属偶氮苯衍生物二阶非线性光学性质的密度泛函理论研究

采用含时密度泛函理论方法(TDDFT)计算了IB族过渡金属及第5周期的金属杂化偶氮苯生色团的二阶非线性光学极化率。研究了金属杂化偶氮苯生色团的电子激发跃迁。结果表明, 与金属离子络合后的杂化偶氮苯生色团, 二阶非线性光学极化率明显改变, 是金属的推拉电子效应的结果。IB族金属的在原有机偶氮苯共轭体系的电荷转移方向的强拉电子效应, 增大了电荷转移范围, 使二阶非线性光学极化率增大。与Nb络合的杂化生色团, 沿原电荷转移相反的方向拉动电荷, 电荷转移跃迁局限于金属离子附近, 未能产生大的激发跃迁偶极矩, 体系的二阶非线性光学响应因而降低。激发跃迁能量是另一个主要影响因素, 同一类跃迁中, 金属杂化生色团的跃迁能量越低, 其二阶非线性光学响应就越大。络合Rh的生色团与Nb杂化生色团类似, 电荷转移跃迁范围都比较小, 同时由于Rh与羧基结合时几乎垂直羧基平面, 电荷同时沿X, Y方向转移跃迁, 属于二维电荷转移类型。     

有机及金属有机苯乙炔树状分子体系的非线性光学性质的理论研究

应用密度泛函理论研究了一系列有机及金属有机苯乙炔树状分子的激发态性质和非线性光学性质。计算的电子吸收光谱显示这些树状分子均在低能区域有一个最强的吸收;此外,金属有机体系的吸收光谱和有机体系相比发生了明显的红移。响应性质的计算结果表明共轭体系的扩展和金属有机基团的引入都使得苯乙炔树状分子的非线性光学极化率显著增加,尤其是含Ru体系,其β和γ值呈数量级增长。对于有机体系和含Pd体系,发生在共轭体系内部的π→π*电荷跃迁是产生分子一阶和二阶超极化率的主要原因。而含Ru体系相当大的非线性响应则主要起源于Ru的轨道到共轭体系的π*的跃迁,同时与Ru相邻的C≡C到共轭体系的π→π*跃迁起着辅助贡献。     

外端为偶氮苯基团的聚酰胺-胺树枝状分子对光和H~+的响应行为

合成了1到5代外端修饰有偶氮苯基团的聚酰胺-胺(PAMAM)树枝状分子.H-NMR、FTIR和元素分析等表明得到了目标产物,外端接枝率在70%~90%.结构分析表明经修饰的PAMAM分子在3代和4代之间存在一个结构转变.UV-Vis和H-NMR分析结构显示,在中性条件下,Gn-azo表现出类似于小分子偶氮苯基团的光响应行为.而在酸性条件下,偶氮苯基团的顺反异构转化率较质子化前低.包裹及释放实验表明,虽然G4-azo包裹水杨酸分子的能力弱于G4PAMAM,但它对于客体小分子具有缓释作用,光照使偶氮苯基团发生由反式到顺式的异构转化之后,缓释效应更明显.     

SYNTHESIS AND CHARACTERIZATION OF NOVEL SOL-GEL DOPED ORGANIC／INORGANIC HYBRID NONLINEAR OPTICAL MATERIALS

4-hydroxy-4 ‘-nitro azobenzene (NHA) and 4-amino-4 ‘-nitro azobenzene (DO3) were prepared respectively from p-nitrophenylamine as a precursor compound. Two kinds of doped organic/inorganic hybrid nonlinear optical (NLO) materials containing NHA and DO3 were synthesized by Sol-Gel process. The preparation and properties of two NLO materials were studied and characterized by FTIR, IH-NMR, UV-VIS, SEM, DSC and SHG measurements. The results show that the maximum doping amounts of NHA and DO3 in two doped hybrid NLO materials are 7.2(wt)% and ll.3(wt)% respectively, and the corresponding second-order NLO coefficients (d33values) are 2.91 ×l0^-3esu and 6.14×10 -8 esu. Two doped NLO materials have relatively good RT stability, after 90 days at RT the d33 values can maintain about 85% of their initial values, but after l0h at 100℃ can only maintain about 50% of their initial values. In this report, the reasons for high-temperature instability of doped materials were discussed, and the possible improvements were also suggested.     

Orientational optical nonlinearity of nematic liquid crystals induced by high-molecular-mass azo-containing compounds

Processes of light-induced reorientation of nematic liquid-crystalline molecules induced by the addition of low concentrations (0.1–2.0 wt %) of comb-shaped polymers and carbosilane dendrimers containing azobenzene fragments are studied. When the molecular structure of the above compounds becomes more complicated, the induced orientational nonlinearity increases. The introduction of 2G and 3G dendrimers into a nematic has for the first time made it possible to visualize and study a purely optical first-order Freedericksz transition in the field of a linearly polarized wave.     

含对硝基偶氮苯胺生色团的键合型有机/无机复合材料的合成及其二阶非线性光学特性

以γ 缩水甘油氧丙基三甲氧基硅烷 (KH5 6 0 )作中间体 ,用溶胶 凝胶 (Sol Gel)法合成了含对硝基偶氮苯胺 (DO3)生色团的新型键合型有机 /无机复合非线性光学 (NLO)材料 ,在这种有机生色团与无机玻璃键合形成的交联网络结构中 ,无机玻璃的刚性三维结构和优良的高温稳定性能有效抑制NLO生色团的极化松弛 .二次谐波信号 (SHG)测量表明 ,合成的键合型聚合物膜的二阶非线性光学系数 (d33)值达 5 79× 10 -7esu ,NLO稳定性也较好 ;在室温下放置 90天后 ,其d33 值能维持初始值的 93 5 % ;在 10 0℃下放置 30 0min后 ,其d33 值仍能维持初始值的 6 0 %     

Syntheses and NLO properties of metal alkynyl dendrimers

Metal-containing (particularly organometallic) dendrimers are briefly introduced, the origin of nonlinear optical (NLO) effects in molecules is briefly summarized, and the syntheses of metal alkynyl dendrimers and progress in employing metal alkynyl dendrimers as NLO materials are reviewed.     

Influence of the central metal ion on nonlinear optical and two-photon absorption properties of push-pull transition metal porphyrins

We present a quantum-chemical analysis of the central metal ion's effect on first hyperpolarizabilities and two-photon absorption (TPA) cross sections at the infrared region of a series of push-pull porphyrins whose synthesis and NLO properties have been reported earlier (J. Am. Chem. Soc. 2005, 127, 9710). The molecular geometries are obtained via the B3LYP/6-31G(d,p) level optimization including SCRF/PCM approach, and the NLO and TPA properties are calculated with the ZINDO/CV method including solvent effects. It is found that the CT transition between the metal ion's d orbital and the macrocycle pi orbitals plays an important role on NLO and TPA properties of metal porphyrins. Our data suggest a new approach to enhance TPA properties of porphyrin materials. We also present a quantum-chemical analysis on porphyrin dimers and trimers to understand the relationship between structural and collective NLO properties. It has been observed that beta values can be improved about an order of magnitude and TPA properties can be enhanced by 2 orders of magnitude by the formation of a trimer. The importance of our results with respect to the design of photonic and photodynamic therapy materials have been discussed.     

Second-harmonic properties of dendritic polymers skeleton-constructed with azobenzene moiety used for nonlinear optical materials

A series of dendrons and dendrimers skeleton-constructed with azobenzene moiety were synthesized and doped in a high T_g polycarbonate (PC) as a host for nonlinear optical (NLO) materials. The optimal loading density and poling conditions were investigated using UV-vis spectral and second-harmonic generation (SHG) measurements. The results showed that the dendrons and dendrimers have good solubility in PC host, which increased with the generation increased. Moreover, the SHG measurements indicated that the dendrons possess higher nonlinearity than the dendrimers. The chromophores of lower generation dendrons were easier to orient along the poling electric field and gave a cone shape with the azobenzene branching units, which coherently contributed to the molecular hyperpolarizability and resulted in the higher SHG intensity. The temporal stability of the dendrons with 15% loading density was also investigated, and showed that the decaying in nonlinearity was slower for higher generation dendrons.     

High‐Generation Second‐Order Nonlinear Optical (NLO) Dendrimers that Contain Isolation Chromophores: Convenient Synthesis by Using Click Chemistry and their Increased NLO Effects

Herein, high‐generation dendrimers G4‐NS and G5‐NS , which contained 30 and 62 azo‐benzene chromophore moieties, respectively, were conveniently prepared in high purity and satisfied yields by a combination of divergent and convergent approaches, coupled with the utilization of the powerful Sharpless click reaction. These dendrimers possessed a regular structure of alternating layers of nitro‐based and sulfonyl‐based azo chromophores in which the sulfonyl‐based azo‐chromophore moieties were utilized as co‐isolation groups for the nitro‐based moieties to achieve larger macroscopic second‐order nonlinear optical (NLO) effects. These high‐generation dendrimers ( G4‐NS and G5‐NS ) displayed very large NLO efficiencies (up to 253.0 pm V^?1), which is, to the best of our knowledge, the record highest efficiency for simple azo‐chromophore moieties.     

Theoretical Studies on the First Hyperpolarizabilities of One-dimensional Donor-bridge-acceptor Chromophores

The ground-state dipole moments and second-order nonlinear optical （NLO） properties of a series of one-dimensional （1D） chromophores with donor-bridge-acceptor （D-B-A） structures have been investigated by using the second-order MФller-Plesset （MP2） and density functional theory （DFT） methods with the basis set of 6-31＋G（d）. According to the calculated results, the relationship between the molecular static first hyperpolarizability （βμ） and the directions of electron transition has been summarized. In terms of the sign of βμ, these 1D organic chromophores were classified into two categories： type Ⅰ with negative βμ and type Ⅱ bearing positive βμ. The analyses show that the remarkable difference of the first hyperpolarizabilities between Ⅰ and Ⅱ chromophores is associated mainly with the electrostatic interaction between terminal groups and the transport electrons in excited states. Moreover, different from the popular viewpoint, the obtained results also show that most of this series of 1D D-B-A molecules are more charge-separated in the ground states than in the excited states. As a whole, this theoretical investigation, to some extent, can be considered as a useful reference in designing the NLO chromophores with large first hyperpolarizabilities.     

Organic sol-gel materials for second-order nonlinear optics based on melamines

A series of all organic nonlinear optical (NLO) sol-gel materials based on melamines and an azobenzene dye (Disperse Orange 3; DO3) have been investigated. Different contents of DO3 were covalently bonded with the melamine-based organic network via condensation of amino and methylol groups. The optically clear samples exhibited second-order optical nonlinearity (second-harmonic coefficient d₃₃) = 35.4 and 11.5 pm/V at 1064 and 1542 nm, respectively) after poling and curing at 220°C for 1 h. Thermal behavior of these organic NLO sol-gel systems was studied by temperature-dependent dielectric relaxation. The results indicate that the incorporation of rigid NLO-active chromophore into the melamine-based matrix leads to high rigidity and dense packing of the organic network. Subsequently, higher glass transition temperatures were obtained for the organic NLO sol-gel material with higher DO3 content. The influence of composition on the temporal stability at 100°C was also investigated. Temporal stability at 100°C was studied as a function of system composition. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2503–2510, 1999     

咪唑氧自由基分子NLO性质的密度泛函理论研究

采用密度泛函理论(DFT) UB3LYP方法, 在6-31g(d)水平上对2,2’-(1,2-乙炔基-4,1-亚苯基)双[4,4’,5,5’-四氢]咪唑氧自由基分子及其异构体的自旋耦合性质进行分析, 并结合有限场(FF)方法计算它们的非线性光学(NLO)系数, 以探讨咪唑氧环在共轭链不同位置时体系的自旋耦合规律和NLO系数. 结果表明, 所有体系基态自旋符合自旋极化规则, 它们的极化率随自旋多重度的增加而减小; 一阶超极化率因受分子对称性影响, 对称性不同其一阶超极化率的变化也不同; 二阶超极化率呈现随着自旋多重度的增加而增加的趋势. 从理论上探讨这些自由基分子自旋耦合规律与NLO活性的关系, 为有机自由基NLO材料的分子设计与实验研究提供一定的理论依据.     

The Design of Second-order Nonlinear Optical Dendrimers: From “Branch Only” to “Root Containing”

Dendrimers are considered as a promising family of organic second-order nonlinear optical (NLO) polymers because of their well-defined structures,easily modified peripheral functional groups,interior branches and central cores.In order to obtain NLO materials with high performance,dendrimer structures have been optimized in the past years,such as the "branch only" and the "root containing" type dendrimers.This feature article highlights the achievements in exploring the rational design of dendrimers,partially marked by their macroscopic NLO performance.     

Theoretical study on a novel series of fullerene-containing organometallics Fe(eta5-C55X5)2 (X = CH, N, B) and their large third-order nonlinear optical properties

Geometry structures, electronic spectra, and third-order nonlinear optical (NLO) properties of Fe(eta (5)-C 55X 5) 2 (X = CH, N, B) have first been investigated by time-dependent density functional theory. We analyzed the intramolecular interactions between ferrocene and the C 50 moiety. The calculated electronic absorption spectrum indicates that the short wavelength transitions are ascribed to the C 50 moiety mixed charge transfer transition of ferrocene itself, while the low energy excitation transitions are ascribed to the unique charge transfer transition from ferrocene to C 50 moiety in these systems. The third-order polarizability gamma values based on sum of states (SOS) method show that this class of ferrocene/fullerene hybrid molecule possesses a remarkably large third-order NLO response, especially for Fe(eta (5)-C 55B 5) 2 with the static third-order polarizability (gamma av) computed to be -10410 x 10 (-36) esu and the intrinsic second hypepolarizability to be 0.250. Thus, these complexes have the potential to be used for excellent third-order nonlinear optical materials. Analysis of the major contributions to the gamma av value suggest that the charge transfer from ferrocene to C 50 moiety along the z-axis (through Fe atom and the centers of two hybrid fullerenes) play the key role in the NLO response. Furthermore, boron substitution is an effective way of enhancing the optical nonlinearity compared to CH and N substitution, owing to smaller energy gap and better conjugation through the whole molecule.     

SYNTHESIS AND OPTICAL PROPERTIES OF A NOVEL ORGANIC/INORGANIC HYBRID NONLINEAR OPTICAL POLYMER VIA SOL-GEL PROCESS*

A new organic/inorganic hybrid nonlinear optical (NLO) material was developed by the sol-gel process of analkoxysilane dye with tetraethoxysilane. A NLO moiety based on 4-nitro-4'-hydroxy azobenzene was covalently bonded tothe triethoxysilane derivative, i.e. γ-isocyanatopropyl triethoxysilane. The preparation process and properties of the sol-gelderived NLO polymer were studied and characterized by SEM, FTIR, ~1H-NMR, UV-Vis, DSC and second harmonicgeneration (SHG) measurement. The results indicated that the chemical bonding of the chromophores to the inorganic SiO_2networks induces low dipole alignment relaxation and preferable orientational stability. The SHG measurements also showedthat the bonded polymer film containing 75 wt% of the akoxysilane dye has a high electro-optic coefficient (r_(33)) of 7.1 pm/Vat 1.1 μm wavelength, and exhibit good SHG stability, the r_(33) values can maintain about 92.7% of its initial value at roomtemperature for 90 days, and can maintain about 59.3% at 100℃ for 300 min.s     

Layer-by-layer deposited organic/inorganic hybrid multilayer films containing noncentrosymmetrically orientated azobenzene chromophores

Organic/inorganic hybrid multilayer films with noncentrosymmetrically orientated azobenzene chromophores were fabricated by the sequential deposition of ZrO2 layers by a surface sol-gel process and subsequent layer-by-layer (LbL) adsorption of the nonlinear optical (NLO)-active azobenzene-containing polyanion PAC-azoBNS and poly(diallyldimethylammonium chloride) (PDDA). Noncentrosymmetric orientation of the NLO-active azobenzene chromophores was achieved because of the strong repulsion between the negatively charged ZrO(2) and the sulfonate groups of the azobenzene chromophore in PAC-azoBNS. Regular deposition of ZrO(2)/PAC-azoBNS/PDDA multilayer films was verified by UV-vis absorption spectroscopy and quartz crystal microbalance measurements. Both UV-vis absorption spectroscopy and transmission second harmonic generation (SHG) measurements confirmed the noncentrosymmetric orientation of the azobenzene chromophores in the as-prepared ZrO2/PAC-azoBNS/PDDA multilayer films. The square root of the SHG signal (I(2omega)(1/2)) increases with the increase of the azobenzene graft ratio in PAC-azoBNS as the number of deposition cycles of the ZrO(2)/PAC-azoBNS/PDDA films remains the same, while the second-order susceptibility chi(zzz)(2) of the film decreases with the increase of the azobenzene graft ratio. Furthermore, the present method was successfully extended to realize the noncentrosymmetric orientation of azobenzene chromophores in multilayer films when small organic azobenzene compounds with carboxylic acid and/or hydroxyl groups at one end and sulfonate groups at the other end were used. The present method was characterized by its simplicity and flexibility in film preparation, and it is anticipated to be a facile way to fabricate second-order nonlinear optical film materials.     

Efficient Nonlinear Optical Properties of Dyes Confined in Interlayer Nanospaces of Clay Minerals

Nonlinear optical (NLO) responses from organic dyes can be maximized when the dyes are aligned in appropriate manners in bulk materials. The use of restricted nanospaces provided by interlayer spacing of inorganic layered materials is a promising strategy for imposing suitable molecular alignments for NLO materials on dyes. The hybrid materials thus obtained exhibit salient NLO responses owing to the improved molecular orientation. In some cases, extension of the π‐electron system as a consequence of improved molecular planarity, obtained by the intercalation of a dye into the 2‐dimensional interlayer space of an inorganic layered material, is also observed as a factor that enhances NLO responses of chromophores at the molecular level. This review focuses on recent progress in the strategies for controlling the molecular orientation of NLO‐phores by employing clay minerals, which are one of the typical inorganic layered materials. In addition, development of a means for fabricating composites that satisfy the properties of an optical material, such as a sufficient size and thickness, a flat surface, and low light‐scattering characteristics is required to utilize the superior NLO properties observed for clay/dye hybrid materials for practical applications. A novel means for obtaining such a hybrid material is also outlined.     

Quantum chemical study of redox-switchable second-order optical nonlinearity in Keggin-type organoimido derivative [PW11O39(ReNC6H5)] n− (n = 2–4)

To analyze the effect of redox state changes on the second-order nonlinear optical (NLO) responses of organoimido-functionalized Keggin-type heteropolyanions, the excitation properties and static second-order polarizabilities of fully oxidized state, the first and second reduced states were calculated by means of the time-dependent density functional theory (TDDFT) method combined with the sum-over-states (SOS) formalism. The incorporation of extra electrons causes significant enhancement in the second-order NLO activity. The reduced complexes show more than three times the efficiency of fully oxidized state. Moreover, the NLO activities for PW₁₁Re^VNPh system can also be modified by controlling the spin multiplicity. The high spin state (³ 3) has twice larger β _vec value than the low spin state (¹ 3). The characteristic of the charge-transfer transition corresponding to the dominant contributions to the β _vec values indicates that metal-centered redox processes influence the intramolecular donor or acceptor character, which accordingly leads to the variations in the computed β values. Owing to the reversible and manipulable redox processes, these kinds of the POM-based hybrid complexes could comprise a promising family of three-state redox-switchable molecular device combining chromic, magnetic, and NLO output.     

三核欠完整立方烷金属原子簇二阶非线性光学性质的理论研究

研究了具有欠完整立方烷构型的过渡金属原子簇分子的二阶非线性光学性质。利用TDDFT方法计算了选取的簇分子及相应模拟构造分子的静态和动态的一阶非线性光学超级化率(ijk);并计算了不同金属、桥原子和配体以及簇芯对该类化合物一阶超级化率的影响。选取其中的一个簇分子为基本模型,分析了该分子的电子结构和分子轨道,在微观水平上阐述了其非线性光学性质的可能起源。认为由过渡金属和硫原子组成的簇芯和与桥原子相连的配体对该类簇合物的二阶非线性光学性质的起决定性的作用。