Structure and third-order nonlinear optical properties of the two-dimensional Co^II coordination polymer [Co(1,2-BIB)(PA)]_n {1,2-BIB is 1,2-bis[(1H-imidazol-1-yl)methyl]benzene and H₂PA is phthalic acid}

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• 作者：Ping Liu ; Qiuxia Liu ; Ning Zhao ; Caixia An and Zhaoxun Lian
• 关键词：optical materials ; Z-scan technique ; two-dimensional coordination polymer ; cobalt(II) ; bis(imidazolyl) ligand ; thin film ; crystal structure ; third-order nonlinear absorption
• 刊名：Acta Crystallographica Section C
• 出版年：2016
• 出版时间：November 2016
• 年：2016
• 卷：72
• 期：11
• 页码：890-894
• 全文大小：620K
• ISSN：1600-5759

文摘

The design of nonlinear optical (NLO) materials with large NLO responses has been a challenge for materials scientists and chemists. Recently, organic polymers have received attention regarding their NLO properties and fast nonlinear response, and clusters involving delocalized dπ–pπ systems and conjugated dπ–pπ systems are expected to be a new class of NLO materials. Metal–organic coordination polymers combine the advantages of the organic and inorganic species. Thus far, tuning the third-order NLO properties of these materials has been a significant challenge. A two-dimensional coordination polymer, namely poly[(μ-benzene-1,2-dicarboxylato-κ³O¹,O^1′:O³){μ-1,2-bis[(1H-imidazol-1-yl)methyl]benzene-κ²N³:N^3′}cobalt(II)], [Co(C₈H₄O₄)(C₁₄H₁₄N₄)]_n, was synthesized by hydrothermal methods. In the structure, the Co^II ion is pentacoordinated by two N atoms from two different 1,2-bis[(1H-imidazol-1-yl)methyl]benzene (1,2-BIB) ligands and three O atoms from two symmetry-related benzene-1,2-dicarboxylate (isophthalate, PA) anions. The pentacoordinated Co^II ions are linked by PA ligands to form a chain structure parallel to the c axis. Adjacent chains are further connected by 1,2-BIB ligands to produce a two-dimensional layered structure. The compound exhibits strong third-order nonlinear absorption and nonlinear refraction effects as a thin film. The third-order susceptibility χ⁽³⁾ is calculated to be 1.07 × 10⁻⁸ esu, which is much larger than the values found for pure inorganic semiconductors and some polymers.