不同溶剂中硝基苯胺分子非线性光学性质的研究

在含时密度泛函理论水平上研究了溶剂对硝基苯胺分子非线性光学性质的影响 .溶剂效应通过极化连续模型来研究 .首先采用极化连续模型在密度泛函理论水平上优化了硝基苯胺分子在溶剂中的几何结构 ,从而研究了溶剂引起硝基苯胺分子几何结构的变化 .然后采用极化连续模型在含时密度泛函理论水平上计算了不同溶剂中硝基苯胺分子的激发态能量和电偶极矩 ,并利用两态模型首次给出了不同溶剂中二次谐波振荡过程的一阶非线性超极化率的色散关系 .计算结果表明 ,极性溶剂对硝基苯胺分子的非线性光学性质有较大的影响 .在低的辐射场频率下 ,理论给出的一阶非线性超极化率的色散关系和实验结果符合得较好 .最后对所得结果从理论上给出了可能的解释并讨论了两态模型的可靠性 .     

有机分子第一超极化率色散效应和双光子共振增强理论研究

采用含时Hartree-Fock和多态求和方法计算了半花菁衍生物生色团的第一超极化率色散效应. 采用二能级模型研究了第一超极化率的双光子共振增强特征. 研究发现，第一激发态对半花菁非线性光学性质起决定性作用，随着入射光波长向短波方向移动，二次谐波产生β(-2ω;ω,ω)不断增大并且在950nm附近出现双光子共振效应，理论结果与实验结果较好相符. 此外，共振条件下的二能级模型需要考虑激发态弛豫效应. 研究结果为实验测量和实际应用提供了理论参考. 关键词： 分子非线性光学 超极化率 色散效应 共振增强     

分子一阶超极化率溶剂效应的理论研究

基于一维谐振子模型建立了极性溶剂对光学二阶非线性分子一阶超极化率产生影响的简化理论模型,推导出了非线性分子的线性极化率α和一阶超极化率β的表达式. 以对硝基苯胺为例,所建立的理论模型计算结果较好地解释了实验获得的溶剂极性对其分子线性吸收峰波长（λ_p）和β值的影响. 关键词： 二阶非线性 溶剂效应 谐振子     

氢键对2-(N-甲基)氨基-5-硝基吡啶分子非线性光学性质的影响

本文在杂化密度泛函理论水平上研究了溶剂对2-(N-甲基)氨基-5-硝基吡啶分子非线性光学性质的影响.在溶剂中,构造了包括氢键作用的超分子体系,在优化结构的基础上分别研究了由极化连续模型模拟的溶剂与该分子的长程相互作用、溶剂与该分子的氢键相互作用以及溶剂与包括氢键作用的超分子体系整体的相互作用对分子的几何结构、非线性光学性质、紫外吸收光谱和电荷分布等特性的影响.结果表明,溶剂中分子电偶极矩、线性极化率和第一超极化率都增大,而溶剂与溶质分子通过氢键形成的超分子结构与单体有着明显区别.因此,氢键对分子结构和性质的影响较大,从而将明显的影响该类分子的非线性光学性质.     

分子一阶超极化率溶剂效应的理论研究

基于一维谐振子模型建立了极性溶剂对光学二阶非线性分子一阶超极化率产生影响的简化理论模型,推导出了非线性分子的线性极化率α和一阶超极化率β的表达式. 以对硝基苯胺为例,所建立的理论模型计算结果较好地解释了实验获得的溶剂极性对其分子线性吸收峰波长（λ_p）和β值的影响.     

二维电荷转移结构轮烯衍生物光学性质理论研究

以一系列轮烯衍生物为目标分子,运用MP2和TD-DFT方法在6-31G(d)基组水平上计算了分子一阶超极化率β和紫外吸收光谱, 研究了分子结构和非线性光学性能的关系. 研究发现, 本文中的二维电荷转移(2DCT)分子2—6均具有较大的β值, 且紫外吸收光谱最大吸收峰和相对应的一维电荷转移(1DCT)分子8和9相比发生蓝移, 这对解决"非线性效率-透光性的矛盾"给予了很大启示. 对于2DCT分子2—7, 分子一阶超极化率的大小和分子构型关系密切, 随着键长交替(BLA)的增加,分 关键词： 轮烯衍生物 二维电荷转移分子 一阶超极化率 紫外吸收光谱     

新型复合物Li…HF,Li…FH,Li…H2O和Li…NH3的一阶超极化率的从头算理论研究

在MP2/6-311 G(2df,2pd)水平上优化得到了几种小型碱金属—极性分子复合物的结构,利用有限场方法[HF,MP2,MP3,MP4(SDQ)]在15种基组上分别计算了它们的偶极矩(μ),极化率(α0),各向异性极化率(Δα)和一阶超极化率(β0).在MP4(SDQ)/6-311 G(2df,2pd)理论水平上,各复合物分子一阶超极化率分别为:Li…HF,β0=3957.575 a.u.;Li…FH,β0=12939.614 a.u.;Li…NH3,β0=34881.899a.u.;Li…H2O,β0=39820.410 a.u..而分子HF,NH3,H2O的一阶超极化率的值分别为1.224 a.u.,35.560 a.u.,20.130 a.u..结果表明,复合物分子中的额外电子对分子非线性光学性质有巨大的贡献.     

有机分子二苯乙烯系列衍生物第一超极化率的理论研究

采用耦合-微扰Hartree-Fock方法(CPHF),计算了二苯乙烯系列衍生物的静态第一超极化率.研究发现,具有离域的共轭体系和电子推拉对结构的分子,有利于发生分子内电荷转移,因而具有大的第一超极化率.进一步研究体系中取代基的位置,给体与受体的数量和得失电子的能力,分子的共面性和对称性对分子第一超极化率的影响,结果表明,有机分子拥有更多数量与更强得失电子能力的给体和受体,最高占据分子轨道(HOMO)和最低未占据分子轨道(LUMO)空间分布的不对称,具有较高的原子共面性和较低的分子中心对称性,都能显著增加 关键词： 二苯乙烯 非线性光学 第一超极化率 空间效应     

半花菁衍生物分子第一超极化率频率色散效应的理论研究

采用含时耦合微扰(TDHF)和多态求和(SOS)方法计算了半花菁衍生物分子生色团4-N,N-dimethylami-no-4′-N′-methylstilbazolium(DAS)的第一超极化率频率色散效应。采用组态相关(INDO/CI)方法计算了分子的前线轨道性质。计算结果表明半花菁衍生物分子最大吸收波长约为480nm,与实验结果十分吻合;第一激发态对体系非线性光学性质起决定作用。在红外波段(800~2500nm),随着基频光频率的增大,二次谐波β(-2ω;ω,ω)和电光效应β(-ω;ω,0)都随之增大,但是β(-2ω;ω,ω)增加的幅度要大于β(-ω;ω,0)。在远红外区β(-2ω;ω,ω)的色散曲线变化比较平缓,到了近红外区(λ<1300nm)共振增强效应逐渐明显。基频光波长为1064nm时,β(-2ω;ω,ω)的含时耦合微扰计算值约为(380±5)×10-30esu。在较高频率时,采用多态求和方法计算应考虑其他态的贡献。此外,还讨论了基组效应对含时耦合微扰计算的影响。     

取代基位置对轮烯衍生物一阶超极化率影响的理论研究

以 [12]轮烯为母体,通过改变取代基的位置构造了一系列轮烯衍生物,运用密度泛函B3YLP方法在6-31G(d)基组水平上计算了分子一阶超极化率β和紫外吸收光谱,研究了分子结构和非线性光学性能的关系. 研究发现,二维电荷转移（2DCT）分子2-5均具有较大的β值,且分子3的紫外吸收光谱最大吸收峰和其余分子相比发生蓝移,这对解决“非线性效率-透光性矛盾”给予了很大启示. 分子2-5的一阶超极化率的大小和分子构型关系密切,随着键长交替(BLA)的增加,分子的β值不断减小.     

DFT-based study of the impact of transition metal coordination on the charge transport and nonlinear optical (NLO) properties of 2-{[5-(4-nitrophenyl)-1,3,4-thiadiazol-2-ylimino]methyl}phenol

Theoretical investigations of the impact of transition metal chelation on the electron/hole-transport and nonlinear optical (NLO) properties of 2-{[5-(4-nitrophenyl)-1,3,4-thiadiazol-2-ylimino]methyl}phenol (L) are reported herein. Calculations were carried out via density functional theory (DFT)-based methods, employing exchange–correlation functionals and basis sets of different qualities. Results have shown that free L is a moderate electron/hole-transporter, but that its Pd(II) and Pt(II) complexes are excellent hole- and electron-transport materials respectively, owing to their very small reorganisation energies and relatively large electronic coupling matrix elements or transfer integrals. These results indicate that the complexes are potentially suitable charge transport materials for the construction of organic light emitting diodes (OLEDs). Nevertheless, the results also revealed a higher NLO activity for L than its metal complexes. Interestingly, the first and second hyperpolarizabilities, along with some computed NLO properties of both L and its complexes are found to be remarkably higher than those of the prototypical push–pull molecule, para-nitroaniline. Accordingly, these compounds are potential candidates for the fabrication of optoelectronic and photonic devices for second- and third-order NLO applications. Summarily, metal chelation is found to enhance the charge transport properties in some cases, and to slightly diminish NLO response of L in all cases investigated.     

Quantum Chemical Calculations on 4-[2-(Tert-Butylamino)-1-Hydroxyethyl]-2-(Hydroxymethyl)Phenol by Density Functional Theory

Density functional theory (DFT) calculations have been carried out for the compound 4-[2-(tert-butylamino)-1-hydroxyethyl]-2-hydroxymethyl) phenol (4BAHEHMP) by using the B3LYP method at the 6-311++G (d,p) basis set level. The electric dipole moment (μ) and the first hyperpolarizability (α) values of the investigated molecule were computed. Total and partial density of state (TDOS and PDOS) and also overlap population density of state (COOP or OPDOS) diagrams analysis were presented. HOMO and LUMO energies confirm that charge transfer occurs within the molecule. In addition Molecular Electrostatic Potential (MEP), Natural Bond Orbital analysis (NBO) and Non- Linear Optical (NLO) properties are studied.     

Coumarin-Pyrazole Hybrid with Red Shifted ESIPT Emission and AIE Characteristics - a Comprehensive Study

The newly synthesized three coumarin pyrazole hybrid excited state intramolecular proton transfer (ESIPT) dyes show efficient charge transfer from the pyrazole ring and the coumarin towards the electron withdrawing dicyanovinylene group as revealed from the frontier molecular orbitals. Aggregation induced emission enhancement (AIEE) studies with 2-((3-(4-hydroxy-2-oxo-2H-chromen-3-yl)-1-phenyl-1H-pyrazol-4-yl)methylene) malononitrile showed 9 fold increase in the emission enhancement in 90% DMF-H₂O mixture. Lippert-Mataga theory explained the solvatochromic behavior of the dyes in various solvents. The charge transfer characteristics and non-linear optical (NLO) properties have been supported and correlated with bond length alternation, bond order alternation and vibrational spectrum. As values of bond order alternation (BOA) tend to be more towards negative and as the value of α increases β decreases while the values of γ depends on the values of α and β. The observed values of γ are positive which revealed that β contributes significantly. The dyes exhibit linear and NLO properties superior to urea. (E)-2-(3-(2-(3-(4-Hydroxy-2-oxo-2H-chromen-3-yl)-1-phenyl-1H-pyrazol-4-yl)vinyl)-5,5-dimethylcyclohex-2-en-1-ylidene) malononitrile shows enhanced linear and non-linear properties among the three dyes.     

Natural Bond Orbital (NBO),Natural Population Analysis (NPA)and Non Linear Optical Properties of (1S,2R)-2-amino-1-phenylpropan-1-ol Using DFT Method

The molecular structure of (1S,2R)-2-amino-1-phenylpropan-1-ol (abbreviated as 2APPO) conformers have been studied in the gas phase. Natural Bond Orbital Analysis and Non Linear Optical properties of 2APPO have been performed by DFT level of theory using B3LYP/6-311++G(d,p) basis set. The atomic charges, electronic exchange interaction and charge delocalization of the molecule have been performed by Natural Bond Orbital (NBO) analysis, Natural Population Analysis (NPA) and Non Linear Optical (NLO) properties have been constructed at B3LYP/6-311++G(d,p) level to understand the optical properties.     

Electronic and structural effects on the nonlinear optical behavior in π‐conjugated structure bis(4‐nitrophenyl) carbonate: a vibrational spectroscopic approach

Fourier transform (FT)‐Raman and infrared (IR) spectra of the nonlinear optical (NLO) material bis(4‐nitrophenyl) carbonate were recorded and analyzed. The geometry, first hyperpolarizability and harmonic vibrational wavenumbers were calculated with the help of Becke3–Lee–Yang–Parr density functional theory method. The detailed interpretation of the vibrational spectra was carried out with the aid of normal coordinate analysis following the scaled quantum mechanical force field methodology. The second‐order NLO properties of the molecule were studied by the Kurtz and Perry powder reflection technique. Stability of the molecule arising from hyperconjugative interactions leading to its NLO activity and charge delocalization were analyzed using natural bond orbital analysis. Copyright © 2010 John Wiley & Sons, Ltd.     

NLO characteristics of D-π-A coumarin-thiophene bridged azo dyes by Z-scan and DFT methods

ABSTRACT

The structural, electronic, intramolecular charge transfer (ICT) and nonlinear optical (NLO) properties of the donor-π-acceptor (D-π-A) azo linked dyes bearing coumarin thiophene bridge with different acceptors were inspected by Z-scan and DFT methods. The dye 3a exhibits bathochromic absorption maxima (649 and 650?nm) in the near IR region in DMF and DMSO. The dye 3a holds low HOMO–LUMO gap elucidated by CV and DFT indicating strong ICT character. The thermal stability is high for 3a and it shows enhanced NLO property by Z-scan and DFT methods as predicted in both global and range-separated hybrid functionals. The molecular geometry was optimised using B3LYP/6-311?+?g(d,p). The ICT characteristics are correlated with NLO properties obtained by Z-scan and DFT techniques.     

Vibrational spectra and structural studies of nonlinear optical crystal ammonium D,L‐tartrate: a density functional theoretical approach

Single crystals of ammonium D , L ‐tartrate, a potential nonlinear optical (NLO) material of interest, were grown by the slow evaporation technique. The crystal structure was determined by single‐crystal X‐ray diffraction. Fourier transform infrared and Raman spectra of the crystallized molecule were recorded and analyzed. The geometry, intermolecular hydrogen bonding, first hyperpolarizability and harmonic vibrational wavenumbers were calculated with the help of B3LYP density functional theory method. The red shift of hydroxyl and NH₄⁺ stretching wavenumbers indicate the formation of inter‐ and intramolecular hydrogen bonding. Simultaneous activation of CH stretching wavenumbers shows the presence of intramolecular charge transfer in the molecule. Natural bond orbital analysis was carried out to demonstrate the various inter‐ and intramolecular interactions that are responsible for the stabilization of this molecule, leading to high NLO activity. Copyright © 2010 John Wiley & Sons, Ltd.     

Photorefractive effect of a novel conjugate polymer containing transition metal complex

The photorefractive effect (PR) of a novels σ-π alternating polymer having 2,2'-bipyridyl in the polymer backbone and their ruthenium complexes has been investigated. The ruthenium complex was used as the charge generator, the σ-π alternating polymer backbone as the charge transporting channel and second-order nonlinear (NLO) optical chromophore. The photorefractive properties were demonstrated by two-beam coupling (2BC), degenerated four-wave mixing (DFWM) and field-induced orientation birefringence at wavelength of 532 nm. This polymer shows a enhanced photorefractive effect due to the efficient photoinduced metal-to-ligand charge transfer (MLCT) inside the ruthenium complex. A net optical gain of about 22 cm^-1 and the diffraction efficiency about 10% were obtained at the external electric field of 30 V/μm. Received 21 December 1999 and Received in final form 7 July 2001     

Computational study of chiral molecules with high intrinsic hyperpolarizabilities

We have investigated the electronic transition, chiroptical properties, and the second-order nonlinear optical (NLO) properties of eight novel chiral diborate compounds and elucidated structure–property relationships from the micromechanism. These compounds show calculated first hyperpolarizabilities (β) ranging from 2738.52 to 83976.45?×?10^?33?esu, which means that subtle structural modifications can substantially enhance the first hyperpolarizability. The cooperativity of intramolecular charge transfer and an effective way to enhance the NLO response were also systemically investigated. The linear correlation between the first hyperpolarizability and the inverse of the electronic transition energy suggests that the electronic transition energy plays a key role in determining the NLO response. These compounds have the potential to be excellent second-order NLO materials from the standpoint of the large β values, high transparency and the intrinsic non-centrosymmetry. The electronic transition and chiroptical properties have been assigned and analysed. The main UV–visible absorption features are best described as π?→?π* transitions. Moreover, the effects of different functionals and basis sets on the first hyperpolarizability were investigated.