溶剂中一、二维电荷转移分子二阶非线性光学性质理论研究

以典型的一、二维电荷转移分子,对硝基苯胺(pNA),1,3-二氨基-4,6-二硝基苯(DADB)分子为例,运用密度泛函理论(DFT)B3LYP和含时耦合微扰(TDHF)方法在6-31+G(d,p)水平上研究了溶剂和入射光频率对目标分子的非线性光学性质的影响.研究发现溶剂分子对分子一阶超极化率β和紫外吸收光谱的影响很大,但对一阶超极化率各向异性比η和退偏比D的影响很小,这是由于随着溶剂相对介电常数的增加,一阶超极化率的分量︱βxxy︱和︱βyyy︱不断增加,且二者具有很好的线性相关性.然而,考虑色散效应后,不同溶剂中分子的一阶超极化率及其各向异性参数都不相同,色散效应对分子一阶超极化率及其各向异性性质均有很大影响.考虑溶剂效应和色散效应后得到的计算结果与实验结果符合得较好.     

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     

Effect of dimer formation via hydrogen bonding on static and dynamic nonlinear optical characteristics of chromophores

The effect of head-to-tail azochromophore dimer formation on the values of static and dynamic first hyperpolarizability is studied on the basis of calculations performed at M06-2X/aug-cc-pVDZ and ωB97X-D/aug-cc-pVDZ computational levels; the results are compared with those obtained at second-order Moller-Plesset pertubation theory (MP2)/aug-cc-pVDZ. Azochromophores DO3 and AAB-DCV , participating in the dimer formation, contain nitro- or dicyanovinylene acceptor moieties. The structure of the studied dimers is obtained at the B3LYP-D3/6-31++G (d,p) level with basis set superposition error (BSSE) correction. Dynamic first hyperpolarizabilities are calculated at radiation frequencies of 0.65 eV, 0.918 eV and 1.165 eV. The essential effect of dimer formation is demonstrated: it results in almost a 3.5 times increase of the first hyperpolarizability. In the series D1 - D2 - D3 , β(2ω) values at 0.65 eV increase in a way similar to the static case: β(2ω) for D2 and D3 are 1.5 and 1.8 times higher than that for D1 . The notable resonance enhancement of β(2ω) for the studied hydrogen-bonded dimers is demonstrated at radiation frequency of 1.165 eV.     

Probing the relationship between spin contamination and first hyperpolarizability: Open‐shell Möbius anion

Möbius strip has attracted extensive interest due to its one‐side structure, special physical and chemical properties. A new extended porphyrin with Möbius structure has been synthesized (St?pień et al., Angew. Chem. Int. Ed. 2007, 46, 7869). In this work, an electron is injected into Möbius to form Möbius anion. For Möbius, four methods (B3LYP, BHandHLYP, CAM‐B3LYP, and LC‐BLYP) obtain the similar first hyperpolarizability (β₀). However, for Möbius anion, four methods obtain very different β₀ values (ranging from 9.85 × 10³ to 8.33 × 10⁵ au). Moreover, the β₀ values of Möbius anion are larger than those of Möbius. Why? The considerable variation (ranging from 0.8162 to 1.7630) of spin contamination (S²) of open‐shell Möbius anion captures our attention. To probe the relationship between S² and β₀, the β₀ values of Möbius anion were calculated using 23 methods. Interestingly, the Hartree‐Fock (HF) composition increases from 0 to 50, the S² value ranges from 0.7522 to 1.3372, and the β₀ value increases from 4.3 × 10³ to 7.36 × 10⁴ au. Further, methods are “dissected” to investigate the effect of HF composition on the S². © 2014 Wiley Periodicals, Inc.     

After the electronic field: Structure,bonding, and the first hyperpolarizability of HArF

In this work, we add different strength of external electric field (E_ext) along molecule axis (Z‐axis) to investigate the electric field induced effect on HArF structure. The H‐Ar bond is the shortest at E_ext = ?189 × 10^?4 and the Ar‐F bond show shortest value at E_ext = 185 × 10^?4 au. Furthermore, the wiberg bond index analyses show that with the variation of HArF structure, the covalent bond H‐Ar shows downtrend (ranging from0.79 to 0.69) and ionic bond Ar‐F shows uptrend (ranging from 0.04 to 0.17). Interestingly, the natural bond orbital analyses show that the charges of F atom range from ?0.961 to ?0.771 and the charges of H atoms range from 0.402 to 0.246. Due to weakened charge transfer, the first hyperpolarizability (β_tot) can be modulated from 4078 to 1087 au. On the other hand, make our results more useful to experimentalists, the frequency‐dependent first hyperpolarizabilities were investigated by the coupled perturbed Hartree‐Fork method. We hope that this work may offer a new idea for application of noble‐gas hydrides. © 2013 Wiley Periodicals, Inc.     

Sum rules for arbitrary-order harmonic generation susceptibilities

Dispersion theory for harmonic generation susceptibilities is considered with the aid of complex analysis. New sum rules are obtained for the powers of arbitrary-order harmonic generation susceptibilities. The theory is based on the holomorphic properties and asymptotic behaviour of nonlinear susceptibilities. The present sum rules are reportedly important in nonlinear optical spectra analysis. Received 19 September 2002 Published online 31 December 2002     

Second and third-order nonlinear optical properties and molecular parameters of azo chromophores: semiempirical analysis

The static and frequency dependent average polarizability (〈α〉), first- and second-hyperpolarizabilities (〈β〉 and 〈γ〉) and highest occupied molecular orbital (HOMO) and lowest occupied molecular orbital (LUMO) energies of nonlinear optical chromophores with nitro acceptors 1–5 have been investigated by using the Austin Model 1 (AM1), Modified Neglect of Diatomic Overlap (MNDO), MNDO with d orbitals (MNDO-d), Parameterization Method 3 (PM3), Recife Model 1 (RM1) and Parameterization Method 6 (PM6) methods within a time-dependent Hartree–Fock (TDHF) approaches. The electronic properties of chromophores 1–5 have been reported by employing two-state model calculated at Zerner's spectroscopic version of the Intermediate Neglect of Differential Overlap singly excited configuration interaction (ZINDO/S-SCI) method. Also, the molecular hardness (η) and electronegativity (χ) parameters have been obtained by using molecular frontier orbital energies. The 〈α〉, 〈β〉, 〈γ〉 HOMO, LUMO energies, η and χ parameters have been investigated with respect to the choice of different semiempirical methods.     

Boron/nitrogen substitution of the central carbon atoms of the biphenalenyl diradical π dimer: a novel 2e-12c bond and large NLO responses

On the basis of the famous staggered biphenalenyl diradical π dimer 1, the eclipsed biphenalenyl (1a), with no centrosymmetry, was obtained by rotating a layer of 1 by 60° around its central axis. Furthermore, the central carbon atoms of 1 and 1a were substituted by boron and nitrogen atoms to form 2 and 2a with a novel 2e-12c bond. We found that the novel 2e-12c bond is formed by the electron pair of the occupied orbital of the phenalenyl monomer substituted by the nitrogen atom and the unoccupied orbital of the phenalenyl monomer substituted by the boron atom. As a result of the novel 2e-12c bond, 2 and 2a exhibit a fascinating interlayer charge-transfer transition character, which results in a significant difference in the dipole moments (Δμ) between the ground state and the crucial excited state. The values of Δμ for 2 and 2a are 6.4315 and 6.9253 Debye, clearly larger than the values of 0 and 0.0015 Debye for 1 and 1a. Significantly, the boron/nitrogen substitution effect can greatly enhance the first hyperpolarizabilities (β(0) ) of 2 and 2a with a novel 2e-12c bond compared with 1 and 1a with a traditional 2e-12c bond: 0 and 19 a.u. for 1 and 1a are much lower than 3516 and 12272 a.u. for 2 and 2a. Furthermore, the interaction energies (E(int) )of 2 and 2a are larger than those of 1 and 1a, which could be considered as a signature of reliability for the newly designed dimers. Our present work will be beneficial for further theoretical and experimental studies on the properties of molecules with the novel 2e-12c bond.     

Influences of microscopic parameters of chiral molecules on the zero-frequency first hyperpolarizabilities

Based on one-electron-on-a-helix model and two-coupled-oscillator model, zero-frequency first hyperpolarizabilities of chiral molecules are investigated. Their expressions and the relations between them and microscopic parameters of chiral molecules are obtained by theoretical derivation. Furthermore, the relations of zero-frequency first hyperpolarizabilities with the wavelength of incident light and microscopic parameters of chiral molecules are simulated numerically. We find the fact that influences of microscopic parameters of chiral molecules on zero-frequency first hyperpolarizabilities are different by using different chiral molecular microscopic parameters such as the helix radius and the helix pitch for one-electron-on-a-helix model and α for two-coupled-oscillator model. Furthermore, the influence of microscopic molecular parameter to the zero-frequency first hyperpolarizabilities can also help to comprehend nonlinear optical mechanism of chiral molecules.     

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.