Li Zong-Jun, Wang Fang-Fang, Li Zhi-Ru, Xu Hong-Liang, Huang Xu-Ri, Wu Di, Chen Wei, Yu Guang-Tao, Gu Feng Long, Aoki Yuriko
State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry Jilin University, Changchun, 130023, China.
Phys Chem Chem Phys. 2009 Jan 14;11(2):402-8. doi: 10.1039/b809161g. Epub 2008 Nov 4.
The interesting radical ion pair salts M(2)(+)TCNQ(-) (M=Li, Na, K) are a particular class of charge transfer complexes with excess electron. The ground states of these complexes are triplet. The C(2v) symmetry geometrical structures of the M(2)(+)TCNQ(-) (M=Li, Na, K) with all-real frequencies are obtained at the density functional theory (DFT) B3LYP/6-31+G(d) level. All calculations of electric properties in this paper have been carried out at the restricted open-shell second order Møller-Plesset perturbation theory (ROMP2) level. Owing to existing excess electron (from the polarized alkali metal atoms) these charge transfer complexes exhibit large nonlinear optical (NLO) responses dominated by excess electron transitions.For these radical ion pair salts M(2)(+)TCNQ(-), the static first hyperpolarizabilities (beta(0)) are large. The order of beta(0) values is 19 203 (M=Li)<24 140 (M=Na) < 29 065 a.u. (M=K). Specially, the second hyperpolarizability (gamma(0)) of the complexes with excess electron is obtained for the first time. These static second hyperpolarizabilities are also large. The order of gamma(0) values is 2,213,006 (M=Li)<3,136,754 (M=Na)<7,905,623 a.u. (M = K). Among the three structures, K(2)(+)TCNQ(-) has the largest gamma(0) value to be 7.9 x 10(6) a.u. (3982 x 10(-36) esu), which is about 9 times larger than that of the intramolecular charge transfer complex sigma-arylvinylidene trans-[Ru(4-C[double bond, length as m-dash]CHC(6)H(4)C[triple bond, length as m-dash]CC(6)H(4)NO(2))Cl(dppm)(2)]PF(6) [Hurst et al., Organometallics, 2001, 20, 4664]. The present investigation provides a new kind of candidates for the high-performance NLO materials.
有趣的自由基离子对盐M₂⁺TCNQ⁻（M = Li、Na、K）是一类特殊的具有多余电子的电荷转移配合物。这些配合物的基态是三重态。在密度泛函理论（DFT）B3LYP/6 - 31 + G(d)水平上获得了具有全实频率的M₂⁺TCNQ⁻（M = Li、Na、K）的C₂ᵥ对称几何结构。本文中所有电学性质的计算都是在受限开壳二阶Møller - Plesset微扰理论（ROMP2）水平上进行的。由于存在多余电子（来自极化的碱金属原子），这些电荷转移配合物表现出以多余电子跃迁为主的大的非线性光学（NLO）响应。对于这些自由基离子对盐M₂⁺TCNQ⁻，静态第一超极化率（β₀）很大。β₀值的顺序为19203（M = Li）＜24140（M = Na）＜29065 a.u.（M = K）。特别地，首次获得了具有多余电子的配合物的第二超极化率（γ₀）。这些静态第二超极化率也很大。γ₀值的顺序为2213006（M = Li）＜3136754（M = Na）＜7905623 a.u.（M = K）。在这三种结构中，K₂⁺TCNQ⁻的γ₀值最大，为7.9×10⁶ a.u.（3982×10⁻³⁶ esu），约为分子内电荷转移配合物sigma - 芳基亚乙烯基反式 - [Ru(4 - C≡CHC₆H₄C≡CC₆H₄NO₂)Cl(dppm)₂]PF₆ [赫斯特等人，《有机金属化合物》，2001年，20，4664]的9倍。本研究为高性能NLO材料提供了一类新的候选物。
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