Anion-Controlled Dielectric Behavior of Homochiral Tryptophan-Based Metal鈥揙rganic Frameworks

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• 作者：Shruti Mendiratta ; Muhammad Usman ; Tzuoo-Tsair Luo ; Bor-Chen Chang ; Shang-Fan Lee ; Ying-Chih Lin ; Kuang-Lieh Lu
• 刊名：Crystal Growth & Design
• 出版年：2014
• 出版时间：April 2, 2014
• 年：2014
• 卷：14
• 期：4
• 页码：1572-1579
• 全文大小：523K
• 年卷期：v.14,no.4(April 2, 2014)
• ISSN：1528-7505

文摘

Three homochiral metal-tryptophanate frameworks, {[Zn₂(l-trp)₂(bpe)₂(H₂O)₂]路2H₂O路2NO₃}_n (1a, l-Htrp = l-tryptophan, bpe = 1,2-bis(4-pyridyl)ethylene), {[Co(l-trp)(bpe)(H₂O)]路H₂O路NO₃}_n (1b), and {[Co(l-trp)(bpa)(H₂O)]路H₂O路NO₃}_n (2, bpa = 1,2-bis(4-pyridyl)ethane), were constructed from Zn²⁺ or Co²⁺ ions, bipyridyl ligands, and the amino acid l-tryptophan (l-Htrp), respectively. Compounds 1a, 1b, and 2 were characterized by single-crystal X-ray diffraction analysis. All of the compounds crystallize in the monoclinic space group P2₁ and form homochiral two-dimensional (2D) layers with rectangle-like (4,4) topologies. Anion-controlled dielectric, luminescence, and nonlinear-optic (NLO) properties were measured for these chiral metal鈥搊rganic frameworks (MOFs) in the solid state. Emission spectra confirmed that compound 1a exhibited a green emission at 546 nm. Dielectric studies of 1a revealed that it had very low dielectric constant (魏 = 2.53 at 1 MHz), thus verifying that it is a promising candidate for interlayer dielectrics. The anion-controlled dielectric properties of 1a were observed after treatment with solutions of different anions. The results revealed a significant change in 魏 value in the case of the phosphate anion. Secondary harmonic generation (SHG) studies revealed that 1a had a good SHG intensity response that was about twice that of SiO₂.