Second-Order Nonlinear Optical Properties of Polyoxometalate Salts of a Chiral Stilbazolium Derivative

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• 作者：Jean-Daniel Compain ; Pierre Mialane ; Anne Dolbecq ; Jrme Marrot ; Anna Proust ; Keitaro Nakatani ; Pei Yu ; Francis Scheresse
• 刊名：Inorganic Chemistry
• 出版年：2009
• 出版时间：July 6, 2009
• 年：2009
• 卷：48
• 期：13
• 页码：6222-6228
• 全文大小：884K
• 年卷期：v.48,no.13(July 6, 2009)
• ISSN：1520-510X

文摘

The synthesis of nonlinear optical (NLO) active salts with stilbazolium derivatives and polyoxometalate (POM) counterions has been investigated. With known nonchiral stilbazolium derivatives, such as MOMS⁺, compounds with centrosymmetric structures have been isolated, like for instance the centrosymmetric salt (MOMS)₄[Mo₈O₂₆] (1), synthesized under hydrothermal conditions. A new chiral derivative of the known DAMS⁺ molecules, named here CHIDAMS⁺, has therefore been synthesized in order to force the crystallization of the hybrid ionic salts in noncentrosymmetric space groups. The CHIDAMS⁺ cation has been crystallized under two polymorphic PF₆⁻ salts, (CHIDAMS)PF₆ (2a and 2b), and its reactivity with various POMs has been investigated. The ionic salt (CHIDAMS)₂[Mo₅O₁₃(OEt)₄(NO){Na(H₂O)_0.5(DMF)_0.5}] (4) crystallizes in the noncentrosymmetric P2₁ group, but the push−pull axis of the CHIDAMS⁺ cations adopts a quasi-antiparallel alignment. The ionic salt (CHIDAMS)₃[PW₁₂O₄₀]·2DMF (5) associating three CHIDAMS⁺ cations and a PW₁₂O₄₀³⁻ Keggin anion crystallizes also in the P2₁ space group, but the disposition of the cations in the solid state is far more favorable. Diffuse reflectance experiments have evidenced a charge transfer between the organic and inorganic components in 5, and Kurtz−Perry experiments show that this salt exhibits a second harmonic generation efficiency more than 10 times higher than those of the PF₆⁻ salts 2a and 2b, the hybrid salt 4, and all of the other NLO active POM molecular materials reported in the literature.