Theoretical study on the second-order nonlinear optical properties of asymmetric spirosilabifluorene derivatives

The equilibrium geometries of four asymmetric spirosilabifluorene derivatives are optimized by means of the DFT/B3LYP method with the 6-31G* basis sets in this paper. On the basis of the optimized structures, the electronic structure and second-order nonlinear optical properties are calculated by using time-dependent density-functional theory (TDDFT) based on the 6-31G* level combined with the sum-over-states (SOS) method. The results show that these compounds possess remarkably larger molecular second-order polarizabilities than typical organometallic and organic compounds, and replacement of a carbon atom with nitrogen within the conjugated substituent has a great influence on the second-order nonlinear optical properties. Analysis of the main contributions to the second-order polarizability suggests that charge transfer from the z-axis directions plays a key role in the nonlinear optical response. These compounds have a possibility to be excellent second-order nonlinear optical (NLO) materials from the standpoint of large beta values, small dipole moment, high transparency, and small dispersion behaviors.     

含Schiff碱基噻唑衍生物二阶NLO性质的理论研究

采用密度泛函理论B3LYP/6-311G**方法,对一系列含Schiff碱基噻唑衍生物的二阶非线性光学(NLO)性质和电子光谱进行了研究.结果表明,分子中推、拉电子取代基强度的提高,噻唑环数的增加以及Schiff碱基的引入有利于提高分子的βtot值.光谱数据显示,分子中HOMO轨道向LUMO,LUMO+2及LUMO+3轨道的电子跃迁对分子的电子光谱有重要贡献.该系列化合物由于具有较大的二阶NLO响应与良好的透光范围,可以作为潜在的NLO材料.     

Theoretical study on the considerable second-order nonlinear optical properties of naphthylimido-substituted hexamolybdates

The static first hyperpolarizabilities and origin of nonlinear optical (NLO) properties of [(2-methylnaphthyl)imido]hexamolybdates derivatives have been investigated by density functional theory (DFT). The [(2-methylnaphthyl)imido]hexamolybdate has considerable large first hyperpolarizability, 6.780 x 10(-30) esu, and it is larger than that of [(2,6-dimethylphenyl)arylimido]hexamolybdate due to the double aromatic rings in the naphthylimido ligand. The naphthylimido ligand acts as an electron-donor and the polyanion acts as an electron-acceptor. The substituent position on the naphthylimido is a key factor to determine the first hyperpolarizability of (naphthylimido)hexamolybdate derivatives. The derivative, which the iodine atom locates on the para nitrogen on the naphthylimido ligand, has the largest betao(o) value among the iodine-substituted derivatives. It suggests that the iodine atom is quasi linear with nitrogen and Mo, which is bonded to thenitrogen atom, could generate a large static electronic field and give the large contribution to NLO response.The introducing of electron-donors significantly enhances the first hyperpolarizabilities of (naphthylimido)hexamolybdates comparing with the electron-acceptors as the electron-donating ability is significantly enhanced when the electron-donor is attached to the naphthylimido segment. The present investigation provides important insight into NLO properties of (arylimido)molybdate derivatives.     

Theoretical investigation on second-order nonlinear optical properties of (dicyanomethylene)-pyran derivatives

On the basis of the ZINDO program, we have designed a program to calculate the second-order nonlinear polarizabilities β_ijk, β₀ and β_μ according to the sum-over-states (SOS) expression. A series of new 4-(dicyanomethylene)-2-methyl-6-(p-dithylamino-styryl)-4H-pyran (DCM) derivatives were designed and their electron spectra and nonlinear optical properties were studied. It is proposed that these compounds possess two important excited states close to each other in energy, both contributing to hyperpolarizability in an additive fashion; 4-(dicyanomethylene)-2,6-bis-(p-donor-styryl)-4H-pyran derivatives are more nonlinear than 4-(dicyanomethylene)-2,6-bis-(p-donor-phenyl)-azo-4H-pyran derivatives. The high nonlinearities, good thermal stability and high transparency make them attractive candidates for second-order nonlinear applications such as electro-optic modulators and frequency doublers.     

Theoretical study on second-order nonlinear optical properties of unsymmetric bis (phenylethynyl) benzene series derivatives

On the basis of ZINDO methods, according to the sum-overstates (SOS) expression, the program for the calculation of the second-order nonlinear optical susceptibilities βijk and βμ of molecules was devised, and the structures and nonlinear optical properties of unsymmetric bis (phenylethynyl) benzene series derivatives were studied. The influence of the molecular conjugated chain lengths, the donor and the acceptor on βμ was examined.     

Synthesis and second-order nonlinear optical properties of push-pull BODIPY derivatives

A series of boron dipyrromethene derivatives bearing an electron-donating 4-(dimethylamino)phenylethynyl group and an electron-withdrawing 4-nitrophenylethynyl group in the opposite 2- and 6-positions have been synthesized by Knoevenagel condensation followed by sequential Sonogashira coupling reactions. The compounds have been fully characterized with various spectroscopic methods. Their electrochemical properties have also been studied by cyclic voltammetry in CH₂Cl₂. It has been found that expansion of the π systems by introduction of the 4-dodecyloxystyryl or 4-(dimethylamino)phenylethynyl group results in lowering of the first oxidation potential, while the first reduction potential remains relatively unaffected. The second-order nonlinear optical properties of these compounds have also been studied by electric-field-induced second-harmonic generation method in CHCl₃. The values of the dot product μ·β are in the range from 94×10^?48 to 330×10^?48 esu at 1907 nm, depending the substituents at the 3- and 5-positions.     

新型双重电荷转移分子的二阶非线性光学性质的 理论研究

以INDO/SCI方法为基础,按完全态求和(SOS)公式编制了计算分子二阶非线性光学系数β~i~j~k和β~μ的程序。研究了1,2-二氨基-4,5-二硝基苯1和其异构体1,3-二氨基-4,6-二硝基苯2的电子光谱和二阶非线性光学性质。计算表明分子1具有与分子2几乎相等的二阶非线性极化率。但由于分子1的偶极矩明显大于分子2的,故分子1的μβ值比分子2的μβ值大的多。在此基础上,研究了2,3-二(β-苯乙烯基)-5,6-二氰基吡嗪和2,3-二(β-噻吩乙烯基)-5,6-二氰基吡嗪和2,3-二(β-噻吩乙烯基)-5,6二氰基吡嗪衍生物的电子光谱和二阶非线性光学性质。结果表明,这些化合物均具有两个相距很近的强吸收峰,它们对β值的呈加和模式。由于这类化合物特征吸收峰均位于413nm以下且具有大的μβ值,所以,它们是一类很有前途的二阶非线性光学候选材料。     

螺旋双芴体系二阶非线性光学性质的ZINDO-SOS理论研究

用密度泛函B3LYP/631G*方法优化螺旋双芴的几何构型,在获得稳定构型的基础上,用半经验ZINDO方法计算体系的激发能和跃迁偶极矩,然后代入完全态求和公式得到体系的二阶极化率.结果表明,螺旋双芴具有较大的二阶极化率、较小的色散行为以及在可见光范围内透明等优点,是具有很好应用前景的非线性光学材料.     

C60PY/TTF(BEDT-TTF)衍生物的电子结构及二阶非线性光学性质的理论研究

用AM1和INDO/CI方法，计算了系列N-甲基-吡咯烷[3，4]C60四硫富瓦烯（C60PY/TTF）的结构和电子光谱，计算结果和实验结果一致。在正确光谱的基础上，用ZINDO/CI-SOS公式计算了该系列分子的二阶非线性光学系数，分析了其分子轨道成分。结果表明，在未占有轨道电子去主要来自C60的贡献，而最高占有轨道的电子云主要集中在TTF上。     

苯并噻二嗪衍生物电子结构和非线性光学性质的研究

运用量子化学PM3方法，对苯并噻二嗪几种衍生物的几何构型、电子结构和前线分子轨道成分进行了分析，研究了电荷分布规律。同时，基于体系中电子转移的特点，利用有限场FF方法探讨了其非线性光学性质的变化。结果表明，苯并噻二嗪分子具有较好的二阶非线性光学性质，并可能成为一类良好的光学材料。     

N－甲基-吡咯烷并[3,4]C60衍生物的结构、电子光谱 和二阶非线性光学性质的 理论研究

利用半经验AM1量子化学方法研究了N－甲基－吡咯烷并[3,4]C60(MPC)及其噻吩取代衍生物(TMPC)的几何结构。电子结构研究表明,MPC及TMPC衍生物的前沿轨道主要由C60部分决定,C60母体与成基团之间存在较强的分子内电荷转移,C60部分是电子受体,而噻吩环部分和吡咯环部分为电子给体。在AM1优化几何构型的基础上,用INDO/SCI方法计算了MPC及TMPC的电子光谱,用完全态求和(SOS)公式计算了其二阶非线性光学性质。结果表明,MPC与TMPC在400nm以上均存在吸收峰,TMPC的这些吸收峰(400nm以上)比MPC的吸收峰强得多,与实验所得结果一致。对于TMPC来说,其二阶非线性光学系数β0值随分子构型不同而有较大的变化,β0值最大可达60×10^-30esu。     

Theoretical investigation of the second-order nonlinear optical properties of helical pyridine-pyrimidine oligomers

The structure and second-order nonlinear optical properties of a series of helical pyridine-pyrimidine oligomers recently synthesized by Barboiu and Lehn have been investigated theoretically by combining molecular mechanics and quantum chemistry approaches. In the absence of substituents, the hyper-Rayleigh scattering response (betaHRS) and the projection of the first hyperpolarizability on the dipole moment (beta||) exhibit periodic variations with chain length, but these nonlinear optical responses remain small. The first hyperpolarizabilities can, however, be enhanced by adding substituents. The greatest enhancement is obtained by substituting the pyrimidine groups by donor groups. Moreover, regular distributions of the donor groups around the helices enable the design of supramolecular structures exhibiting dipolar, octupolar or Lambda-shaped nonlinear optical characters, evident from the values of the depolarization ratios in hyper-Rayleigh scattering. Therefore this theoretical investigation demonstrates the potential of helical structures for the organization of chromophores in such a way that they exhibit large and specific second-order nonlinear optical responses.     

N-取代吩噻嗪衍生物分子的结构和二阶非线性光学性质的理论研究

在ZINDO方法基础上, 按完全态求和(SOS)公式, 编制了计算分子二阶非线性光学系数βijk的程序。研究了各种取代基在吩噻嗪的氮上取代后衍生物的结构和二阶非线性光学系数。结论是N上取代推电子基对增大二阶光学非线性有利, N上取代吸电子基对增大二阶光学非线性不利。扩大共轭范围对增大二阶光学非线性有利。对上述结果在微观上给予了解释。     

反式-双(二甲基苯膦)铂配合物二阶非线性光学性质的密度泛函理论研究

采用密度泛函理论B3LYP方法,在6-31G(d)的水平上对两种反式-双(二甲基苯膦)铂配合物的几何构型进行优化,在获得稳定构型基础上,利用TD-B3LYP方法得到体系的UV-Vis吸收光谱,并用有限场(FF/B3LYP)方法探讨体系的二阶非线性光学性质(NLO).结果表明,此类铂配合物具有较大的二阶极化率,以及在可见光范围内透明等优点,是具有很好应用前景的非线性光学材料.     

Theoretical study of static second-order nonlinear optical properties of push–pull heteroquinonoid dimers

The static first-hyperpolarizabilities (β) of a number of donor–acceptor substituted heteroquinonoid dimers has been calculated analytically by using the time-dependent Hartree Fock (TDHF) method and split-valence basis sets. The evolution pattern of β of mono-substituted quinoid rings has been found to mirror the pattern of variation of β of the corresponding polyenes. The charge transfer (CT) characteristics of the chosen quinonoid chromophores have been studied in terms of effective CT parameters which have been found to fairly correlate with the calculated β of mono-substituted quinonoids. The relative trend in β of quinonoid dimers has been rationalized on the basis of calculated hardness parameter η and which exhibit linear relationships with the ZINDO-S/CI calculated vertical transition energy corresponding to HOMO→LUMO excitation. The analytically evaluated response property, β correlates fairly with the corresponding two-state calculated β₀ and relevant spectroscopic quantities. The general qualitative trend in β obtained for 3-21G and 6-31G** basis sets has been found to be same. The aromatic factor does not play any significant role in the evolution of second-order NLO responses in heteroquinonoid compounds.     

Azo-azulene derivatives as second-order nonlinear optical chromophores

The molecular and solid state nonlinear optical (NLO) properties of several (phenylazo)-azulenes are investigated. In particular, (4-nitrophenylazo)-azulene (2b) exhibits a quadratic hyperpolarizability (beta(vec)) of 80 x 10(-30) cm5esu recorded at 1.907 microm by the electric field-induced second-harmonic (EFISH) technique. This molecular material, which crystallizes in the monoclinic noncentrosymmetric space group Pc, exhibits an efficiency 420 times that of urea in second-harmonic generation. The origin of the optical nonlinearity in azo-azulene is discussed in relation with crystal structures and semiempirical calculations within the INDO/SOS formalism, and compared with that of the well known disperse red one (DR1) organic dye.     

DFT study on second-order nonlinear optical properties of the derivatives of 7-vertex cobalt–carborane metallocenyl

Density functional theory (DFT) B3LYP method was employed to calculate electron properties and the second-order nonlinear optical (NLO) responses of the derivatives which were formed by (C₅H₅)Co(C₂B₄H₆) and CHCHC₆H₄NO₂, CHCHC₆H₄NH₂. The results show: when H atom of (C₅H₅)Co(C₂B₄H₆) is substituted by CHCHC₆H₄NO₂, the β_tot values of isomers are all slightly smaller than that of ferrocene (Fc) derivative (FcCHCHC₆H₄NO₂). However, when H atom of (C₅H₅)Co(C₂B₄H₆) is substituted by CHCHC₆H₄NH₂, the β_tot values of isomers are close to that of ferrocene (Fc) derivative (FcCHCHC₆H₄NH₂). It indicates that (C₅H₅)Co(C₂B₄H₆) can be either a donator or an acceptor.     

不对称二苯乙炔系列衍生物的二阶非线性光学性质的ZINDO-SOS 研究

在ZINDO方法基础上,按完全态求和(SOS)公式编制了计算分子二阶非线性光学系数β~i~j~k,β~μ的程序;研究了不对称二苯乙炔系列衍生物的结构和非线性光学性质;计算了不对称二苯乙炔系列衍生物的UV光谱,偶极矩,β~μ,β~0,μβ,μβ~0,及激发态电荷转移;考察了分子共轭链长、给电子基团对β~μ的影响。并对上述结果在微观上给予了解释。     

Theoretical study of the second-order nonlinear optical properties of [N]helicenes and [N]phenylenes

The second-order nonlinear optical properties of helicenes and phenylenes have been theoretically investigated at the time-dependent Hartree-Fock level using the Austin model 1 semiempirical Hamiltonian. Both the antisymmetric isotropic component of the first hyperpolarizability (beta) and its projection on the dipole moment (beta(parallel)) have been determined for increasingly large helical systems as well as for their analogs substituted by donor/acceptor pairs. It is found that (i) in nonsubstituted helicenes and phenylenes, beta increases monotonically with the size of the system and slightly depends on the nature of the helix; (ii) the corresponding beta(parallel) is mostly determined by the radial component of the first hyperpolarizability vector; (iii) in helicenes, beta(parallel) is positive and presents quasiperiodic oscillations with the helix; (iv) in phenylenes, beta(parallel) depends upon the size of the helix and it can be either positive or negative as a result of the differences in evolution with N of the radial components of the dipole moment and first hyperpolarizability. Substituting the helicenes and phenylenes by the prototypical NH2/NO2 donor/acceptor pair provides a diversity of effects on beta and beta(parallel) that encompasses decrease, increase, and change in sign.     

Theoretical study of the conjugation length effect on the electronic and second-order nonlinear optical properties of amino–nitro diphenylacetylenes

We presnet a theoretical study of the effect of the conjugation length on the electronic properties and second-order molecular polarizabilities β in p-amino-p′-nitrodiphenylacetylene molecules where the number of triple bonds in the conjugated segment varies from 1 to 4. The β values are calculated via an intermediate neglect of differential overlap/single configuration interaction (INDO /SCI ) sum-over-states (SOS ) approach. We test the convergence of the SOS method and the validity of the two-state model to describe the β response. The results indicate that increasing the conjugation length results in a decrease of the charge transfer within the molecule. The two-state model is shown to break down as the conjugated segment extends to four triple bonds; this is due to the appearance of several low-lying nearly isoenergetic excited states that significantly contribute to the β response. The theoretical results are in excellent agreement with recent experimental data. © 1994 John Wiley & Sons, Inc.