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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Anion complexation with cyanobenzoyl substituted first and second generation tripodal amide receptors: crystal structure and solution studies
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Anion complexation with cyanobenzoyl substituted first and second generation tripodal amide receptors: crystal structure and solution studies

机译：阴离子与氰基苯甲酰基取代的第一代和第二代三脚架酰胺受体的络合：晶体结构和溶液研究

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Anion complexation properties of two new tripodal amide receptors have been extensively studied here. Two tripodal receptors have been synthesized from the reaction of cyanobenzoyl acid chloride with two tri-amine building blocks such as (i) tris(2-aminoethyl)amine and (ii) tris(2-(4-aminophenoxy)ethyl)amine, which resulted in the first (L-1) and second (L-2) generation tripodal amides respectively. A detailed comparison of their coordination behavior with anions is also described by crystallographic and solution state experiments. The crystal structure demonstrates various types of spatial orientations of tripodal arms in two receptors and concomitantly interacts with anions distinctively. Intramolecular H-bonding between amide N-H and C=O prevents opening of the receptor cavity in the crystal, which leads to a locked conformation of L-1 having C-3v symmetry and makes amide hydrogen unavailable for the anion which results in side cleft anion binding. However, in L-2 we conveniently shift the anion binding sites to a distant position which increases cavity size as well as rules out any intramolecular H-bonding between amide N-H and C=O. The crystal structure shows a different orientation of the arms in L-2; it adopts a quasi-planar arrangement with C-2v symmetry. In the crystal structure two arms are pointed in the same direction and while extending the contact the third arm is H-bonded with the apical N-atom through a -CN group, making a pseudo capsular cavity where the anion interacts. Most importantly spatial reorientation of the receptor L-2 from a C-2v symmetry to a folded conformation with a C-3v symmetry was observed only in the presence of an octahedral SiF62- anion and forms a sandwich type complex. Receptors L-1 and L-2 are explored for their solution state anion binding abilities. The substantial changes in chemical shifts were observed for the amide (-NH) and aromatic hydrogen (-CH) (especially for F-), indicating the role of these hydrogens in anion binding. The anion interacts with receptor L-2 more strongly than L-1 as confirmed by H-1 NMR titration upon monitoring the -NH signal.
机译：在这里已经广泛研究了两种新的三脚酰胺受体的阴离子络合特性。由氰基苯甲酰氯与两个三胺结构单元如（i）三（2-氨基乙基）胺和（ii）三（2-（4-氨基苯氧基）乙基）胺反应合成了两个三脚受体。分别产生了第一代（L-1）和第二代（L-2）三脚酰胺。还通过晶体学和溶液状态实验描述了它们与阴离子的配位行为的详细比较。晶体结构显示了三脚架臂在两个受体中的各种类型的空间取向，并与阴离子显着地相互作用。酰胺NH和C = O之间的分子内H键可防止晶体中受体腔的打开，从而导致具有C-3v对称性的L-1的锁定构象，并使酰胺氢不可用于阴离子，从而导致侧裂阴离子捆绑。但是，在L-2中，我们可以方便地将阴离子结合位点移至远处，这会增加空腔的大小，并排除了酰胺N-H和C = O之间的任何分子内H键。晶体结构在L-2中显示出不同的臂取向;它采用具有C-2v对称性的准平面排列。在晶体结构中，两个臂指向相同的方向，并且在扩展接触时，第三个臂通过-CN基团与顶端N原子H键合，形成一个与阴离子相互作用的假囊腔。最重要的是，仅在八面体SiF62-阴离子存在下，受体L-2从C-2v对称空间折叠到具有C-3v对称的折叠构象，并形成夹心型复合物。研究了受体L-1和L-2的溶液状态阴离子结合能力。观察到酰胺（-NH）和芳族氢（-CH）（特别是F-）的化学位移发生了实质性变化，表明这些氢在阴离子结合中的作用。在监测-NH信号时，通过H-1 NMR滴定证实，该阴离子与受体L-2的相互作用比L-1更强烈。

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