Sulfonyl-bridged oligo(benzoic acid)s: synthesis, X-ray structures, and properties as metal extractants
Sulfonyl-bridged oligo(benzoic acid)s: synthesis, X-ray structures, and properties as metal extractants
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DOI：
10.1007/s10847-012-0283-9
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发表时间：
2014-04
影响因子：
2.3
通讯作者：
Naoya Morohashi;K. Nagata;Tomoko Hayashi;T. Hattori
中科院分区：
文献类型：
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作者：
Naoya Morohashi;K. Nagata;Tomoko Hayashi;T. Hattori
磺酰基桥连的低聚（苯甲酸）s7 n（n= 2-4）由硫桥连的低聚酚的相应的三氟甲磺酸酯（8 n）通过三氟甲磺酸酯部分的钯催化的甲氧基羰基化，随后通过所得甲酯的水解和随后的硫桥的氧化来制备。X射线衍射分析表明，二聚体72通过羧基间的氢键形成了超分子锯齿形链。对于三聚体73的晶体，两个分子通过末端羧基和中心羧基之间的两对分子间氢键缔合形成环状二聚体，该环状二聚体与两个相邻的二聚体以及剩余的羧基连接，构成无限长的柱状结构。四聚体74通过末端羧基之间的分子内氢键形成单分子环状结构，分子与相邻两个分子之间通过内部羧基和磺酰基之间的两对分子间氢键连接。溶剂萃取实验表明，低聚（苯甲酸）对镧系离子（Ln 3+）表现出较高的萃取能力;性能遵循顺序74 <$73>72。对于Pr 3+、Gd 3+和Yb 3+的萃取，观察到中等的萃取选择性。在Et 3 N存在下，由74（H4 L）和Tb（NO3）3·6 H2O合成的簇合物[Tb 4L 4（H2O）6]（Et 3 NH）4的X射线晶体学分析表明，没有磺酰氧与金属中心配位。这表明74的高萃取性源于磺酰基官能团的吸电子性质，这增加了两个相邻羧基的酸性。
Sulfonyl-bridged oligo(benzoic acid)s7n(n= 2–4) are prepared from the corresponding triflate esters (8n) of sulfur-bridged oligophenols by palladium-catalyzed methoxycarbonylation of the triflate moieties, followed by hydrolysis of the resulting methyl esters, and subsequent oxidation of the sulfur bridges. X-ray analysis reveals that dimer72forms supramolecular zig-zag chains through intermolecular hydrogen bonds between the carboxy groups. As for the crystal of trimer73, two molecules are associated through two couples of intermolecular hydrogen bonds between terminal and central carboxy groups to form a cyclic dimer, which connects with two adjacent dimers with the remaining carboxy groups to construct an infinite columnar structure. Tetramer74adopts a monomolecular cyclic structure through intramolecular hydrogen bonds between the terminal carboxy groups, and a molecule connects with each of two adjacent molecules through two couples of intermolecular hydrogen bonds between inner carboxy and sulfonyl groups. Solvent extraction experiments reveal that the oligo(benzoic acid)s exhibit high extractability toward lanthanoid ions (Ln3+); the performance follows the order74≈73>72. Moderate extraction selectivity is observed for the extraction of Pr3+, Gd3+, and Yb3+with72. X-ray crystallographic analysis of cluster [Tb4L4(H2O)6](Et3NH)4, which was prepared from74(H4L) and Tb(NO3)3·6H2O in the presence of Et3N, reveals that no sulfonyl oxygens coordinate to the metal centers. This indicates that the high extractability of74originates from the electron-withdrawing nature of the sulfonyl function, which increases the acidity of two adjacent carboxy groups.