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.     

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。     

Effect of conjugated length on the calculated nonlinear second-order optical susceptibilities of some organic molecules

Calculations of the nonlinear second-order optical susceptibilities (β_ijk) for disubstituted conjugated organic molecules are reported. The calculations are performed using the semiempirical INDO /CI method combined with a sum-over-states expression for β_ijk. The calculated results show that the second-order static susceptibility (β₀) varies as the 2.6 power of the length of the conjugated π-electron system. Furthermore, it is found that the amount of substituent charge transfer from ground state to first excited state decreases with inccreasing chain length. A limiting value of β₀ with the length of the conjugated system is discussed.     

系列新推拉型多环共轭分子二阶非线性光学性质的理论研究

在AM1和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_ijk和β_μ的程序,研究了一系列新推拉型多环共轭分子的结构、光谱和二阶非线性光学系数β(-2ω,ω,ω)和β(0,0,0).考察了分子共轭链长、分子骨架和给电子取代基对β_μ的影响,并设计了具有最大β_μ的新型非线性光学材料分子.     

Synthesis,Structure, and Nonlinear Optical Properties of Cross‐Conjugated Perphenylated iso‐Polydiacetylenes

Monodisperse, cross‐conjugated perphenylated iso‐polydiacetylene (iso‐PDA) oligomers, ranging from monomer 15 to pentadecamer 25 , have been synthesized by using a palladium‐catalyzed cross‐coupling protocol. Structural characteristics elucidated by X‐ray crystallographic analysis demonstrate a non‐planar backbone conformation for the oligomers due to the steric interactions between alkylidene phenyl groups. The electronic absorption spectra of the oligomers show a slight red‐shift of the maximum absorption wavelength as the chain length increases from dimer 17 b to pentadecamer 25 , a trend that has saturated by the stage of nonamer 22 . Fluorescence spectroscopy confirms that the pendent phenyl groups present on the oligomer framework enhance emission, and the relative emission intensity consistently increases as a function of chain length n. The molecular third‐order nonlinearities, γ, for this oligomer series have been measured via differential optical Kerr effect (DOKE) detection and show a superlinear increase as a function of the oligomer chain length n. Molecular modeling and spectroscopic studies suggest that iso‐PDA oligomers (n>7) adopt a coiled, helical conformation in solution.     

1，3方酸嵌入对称二苯乙烯衍生物的三阶非线性光学性质的理论研究

以量子化学MP3优化构型为基础,利用INDO／CI方法研究系列嵌入1,3方酸的对称二苯乙烯衍生物的电子光谱,并利INDO／CI－SOS方法计算系列化合物的三阶非线性光学系数γ（-ω;ω,-ω,ω)和γ（0,0,0,0）值,探讨了γ和分子结构之间的关系。理论计算结果表明,在双推电子基团取代二苯乙烯衍生物中适当地嵌入方酸,可使其三阶非线性光学系数有所增加,达到并保持其透明性。     

若干有机非线性光学材料的分子设计及三阶非线性光学性质的理论研究

以ＩＮＤＯ／ＳＣＩ方法为基础,利用完全态求和（ＳＯＳ）公式,计算了若干有机非线性光学材料分子的三阶非线性光学系数γ（－ω; ω, －ω, ω）和γ（０; ０, ０, ０）,研究了γ与分子骨架、给电子取代基、噻吩环数目即：共轭分子链长的关系。设计了较大γ的新型非线性光学材料分子。     

含噻吩环的新推-拉型多环电光聚合物中间体的三阶非线性光学系数的理论研究

以INDO/SCI方法为基础,利用完全态求和(SOS)公式,计算了一系列新推-拉型多环电光聚合物中间体的三阶非线性光学系数γ(一ω;ω,-ω,ω)和γ(0;0,0,0),研究了γ与分子骨架、给受取代基和噻吩环数目(共轭分子链长的关系)及其与外场频率的关系,表明在链不十分长时,γ与链长的2.69次方成正比。     

C60-吡咯烷衍生物的合成及非线性光学性质的研究

通过富勒烯C₆₀与肌氨酸和有机醛化合物的1,3-偶极环加成反应, 获得了九种含不同有机功能基团的C₆₀吡咯烷衍生物1～9, 用¹H NMR, ¹³C NMR, FTIR, UV-vis和FAB-MS进行了结构表征; 利用皮秒激光光源, 采用z扫描技术测定了分子的三阶非线性超极化率γ⁽³⁾, 结果显示: 化合物3 (γ⁽³⁾＝4.14×10^－33 esu)具有最大的三阶非线性光学系数, 说明增加噻吩共轭链的长度, 使三阶非线性活性增加; 对具有相同共轭链的C₆₀-噻吩吡咯烷衍生物(2, 5, 1和4), 吸电子取代基减小了三阶光学非线性活性, 给电子基增大了三阶光学非线性活性; 同时发现喹啉环2-位键联(7)比4-位(8)有更好的三阶光学非线性活性.     

Synthesis of third‐order non‐linear optical polymers based on conjugated poly(heteroarylene methines)

A series of 10 new poly(heteroarylene methylenes) containing one pyrrole or thiophene ring alternating with a carbon atom in the main chain were synthesized and characterized. The polymers which were synthesized in the air were found to be partially dehydrogenated by the oxygen, that is, the bridge carbon atoms between pyrrole or thiophene rings were partially sp³ atoms and partially sp² atoms. However the polymers which were synthesized in the flowing nitrogen atmosphere were found to be deoxidized, that is the bridge atoms were sp³ atoms. The deoxidized polymers could be oxidatively dehydrogenated with tetrchlorobenzoquinone. These polymers are useful model systems to investigate the effect of conjugation length on the electronic and optical properties of conjugated polymers. Third‐order optical non‐linearities of the reulting polymers were studied by z‐scan techniques. The results show that the reulting polymers exhibited large third‐order optical non‐linear susceptibilities as large as 10^?8 esu. Copyright © 2004 John Wiley & Sons, Ltd.     

若干有机共轭分子二阶非线性光学系数和结构的关系

利用CNDO/S-CI程序计算了四类结构近似的有机共轭分子的二阶非线性光学系数,系统地研究了分子结构、共轭链链长、取代基的电子性质、取代位置等对有机共轭大分子二阶非线性光学性质的影响。研究结果表明,四类化合物的二阶非线性光学性质与其分子结构有着密切的关系。     

Synthesis of ladder polymers containing polydiacetylene backbones connected with methylene chains and their optical properties

The polymers consisting of polydiacetylene (PDA) backbones were obtained from the novel monomer derivatives, R CC CC R′ CC CC R [where R =  (CH₂)₄OCONHCH₂COOC₄H₉, R′ =  (CH₂)_n ; n = 2, 4, 8] [4BCMU4A(n)], in which linear methylene chain is sandwiched between two diacetylene moieties by solid-state 1,4-addition reaction. The polymerization process was investigated in detail by using spectroscopic techniques such as solid-state ¹³C-NMR, visible absorption, and IR absorption spectra. It was estimated that the polymerization of 4BCMU4A(8) and 4BCMU4A(4) takes place by two consecutive 1,4-addition reactions to form two PDA backbones, which constitute the two poles of the respective ladders. The bridging methylene chain length in the monomer was found to play a vital role as far as the polymerization process is concerned. Thus, the monomers with eight or four methylene units could form the ladder–PDAs by a two-step process, whereas the monomer containing two methylene units could only undergo one-step of 1,4-addition reaction. Further, it was found that the crystallinity of the polymers depends on the methylene chain length in the monomers, 4BCMU4A(8) being the most crystalline of all. These structural features strongly affect their absorption spectra. The third-order nonlinear optical susceptibilities (χ⁽³⁾) for these polymers were measured using third-harmonic generation method. The largest χ⁽³⁾ value obtained was 3.4 × 10⁻¹¹ esu for the poly[4BCMU4A(8)] thin film in resonant region. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3537–3548, 1999     

C~6~0-TTF及其衍生物的二阶非线性光学性质的理 论研究

采用ZINDO系列方法优化了环状桥联的C~6~0-TTF分子及其6个衍生物的几何构型,研究了各分子的稳定构型并以稳定构型为基础,计算了这些分子的电子光谱,二阶非线性光学系数β~μ,β~0,及激发态电荷转移,考察了取代基变化对β~μ的影响,并对上述结果在微观上给予了解释。     

A simplified three-level model describing the molecular third-order nonlinear optical susceptibility

A simplified three-level model for γ, the molecular third-order nonlinear optical susceptibility, is presented and discussed. The perturbation theory-based approach suggests that there are three primary avenues to optimizing molecular four-wave mixing susceptibilities and that with each of these is associated a particular class of molecular electronic structures. The three electronic structure classes consist of (1) conjugated donor–acceptor dipolar molecules with a large secondorder susceptibility, β; (2) even-member conjugated chains such as -enes, -ynes, and ene–ynes with large two-photon dominated susceptibilities; and (3) “charged” odd-member conjugated chaines with large linear absorption dominated third-order susceptibilities such as squaryliums (perhaps, more generally, the polymethine dyes). Classes (1) and (2) have been known and investigated in the past, while recent results of ours suggest the existence of the third and perhaps final class.     

螺旋共轭化合物的结构光谱和二阶非线性光学性质的理论研究

用ＡＭ１和ＩＮＤＯ／ＣＩ方法研究了螺旋共轭化合物（ｎ＝１～５）的结构和电子光谱,并在此基础上,用完全态求和公式（ＳＯＳ）自编程序计算了二阶非线性光学系数,从理论上研究了１,４－环己二烯环数增加时对二阶非线性光学性质的影响     

Theoretical Studies on Electronic Spectra and Second-order Nonlinear Optical Properties of Glucosyl Substituted Barbituric Acid Derivatives

AMI semi-empirical method was used to optimize the barbituric acid derivatives substituted with glucosyl B1-5 （series B）, and the thiobarbituric acid derivatives substituted with glucosyl T1-5 （series T）. Based on the optimized structures, INDO/CI method was adopted to calculate the electronic spectra. Meanwhile, the second-order nonlinear optical （NLO） coefficients βμ were calculated with the sum-over-state （SOS） formula. The results show that when the number of glucosyl units was increased, ｜βμ｜ values of the barbituric and thiobarbituric acid derivatives were both enhanced, especially for thiobarbituric acid derivatives. It indicates that non-conjugated substituted group could also improve NLO properties of materials when the number of repeated units was increased. Additionally, the absorption bands appearing in UV area are consistent with the proper change of the number of glucosyl units, and consequently it can be concluded that the high transparencies of all systems were scarcely varied.     

Theoretical study on a series of push–pull molecules grafted on methacrylate copolymers serving for nonlinear optics

The B3LYP functional combined with 6‐31G(d) basis set have been designated as the most appropriate for structural investigations of a new range of organic conjugated push–pull molecules containing numerous electron donor/acceptor couples in their ends. Second‐order Møller Plesset has been used to properly reproduce nonlinear optical (NLO) properties and to study the alkyl chain length effect of these systems. Satisfactory dynamic hyperpolarizabilities at the wavelength 1064 nm are obtained with values in the order of 11,500 × 10^?30 esu. Then, the study has been extended to monomers generated by combination of the chromophores to either acryloyl chloride or 4‐hydroxy‐styrene sequences. Then, the obtained molecules have been grafted to a methyl methacrylate copolymeric chain, the resulting values of β(1064 nm) have been demonstrated to be sensitive to these modifications. © 2012 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Theoretical Investigations on the Electronic and Optical Properties of Luminescent Poly（alkylthiophene-co-pyridine）

Quantum-chemical techniques were applied to investigate a series of conjugated polymers： poly（3-octylthien-2,5-ylene-co-pyrid-2,6-ylene） （pl）, poly[pyrid-2,6-ylenebis（3-octylthien-2,5-ylene）] （p2） and poly[pyrid-2,5-ylenebis（3-octylthien-2,5-ylene）] （p3） comprising alternating n-excessive 3-alkylthiophene and n-deficient meta- or para-linked pyridine moieties. Their ground state and excited state structures were optimized with density functional theory B3LYP method, and the optical properties were calculated by the time-dependent density functional theory （TD-DFT） and ZINDO/S methods. Their HOMO-LUMO gaps （An-L）, the lowest excitation energies （Eex）, ionization potentials （IP） and electron affinities （EA） were obtained by extrapolating those of the polymers to the inverse chain length equal to zero （1/n=0）. The calculated results showed that the decrease of pyridylene content increased the HOMO level and decreased the LUMO level while the para-linkage further contributed to it. The IP are in the order： p1〉p2〉p3 but EA are： p1〈p2〈p3. In addition, the decrease of the pyridylene content and the para-linked pyridylene in the backbone of the polythiophene resulted in a narrowed energy gap and bathochromic absorption and emission peaks.     

Synthesis and properties of a second‐order nonlinear optical side‐chain polyimide

A thermal stable aromatic polyimide (PI) with side‐chain second‐order nonlinear optical (NLO) chromophores has been developed. The PI was prepared by the ring‐opening polyaddition of 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride with a new diamine having two N‐ethyl‐N‐[4‐[(6‐chlorobenzothiazol‐2‐yl)diazenyl]phenyl]‐2‐aminoethanol units as the NLO chromophore, followed by poling during or after the thermal imidization process. The resulting PI had number and weight‐average molecular weights (M_n, M_w) of 25,000 and 80,000, respectively, and a relatively high glass transition temperature of 180°C. The second harmonic coefficient (d₃₃) of PI at the wavelength of 1.064 μm was 138 pm/V (329.6 × 10⁻⁹ esu) and remained unchanged at elevated temperatures. The corona poling process of the NLO‐substituted poly(amic acid) to the PI was also studied in detail by measuring the second harmonic generation (SHG) from the polymer films. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1321–1329, 1999