Tetraanionic organoborate squares glued together by cations to generate nanotubular stacks
Tetraanionic organoborate squares glued together by cations to generate nanotubular stacks
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DOI：
10.1002/anie.200503156
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发表时间：
2006-01-01
影响因子：
16.6
通讯作者：
Robson, R
中科院分区：
文献类型：
--
作者：
Abrahams, BF;Price, DJ;Robson, R
LH 4与B（OMe）3和三乙胺（Et 3 N）在甲醇中于160 ℃在密封管中反应生成溶剂化的（Et 3 NH）4 [B4 L4]晶体。[3a晶体结构包含离散的分子[B4 L4] 4 <$正方形，如图1所示，其中所有四个L4 <$单元具有相同的手性。正方形中心的B∑∑ B间距为13.22。所有手性相同的有机硼酸盐正方形在垂直于B4平面的方向（即c方向）上一个在另一个的顶部上堆叠，其中一个正方形的带负电荷的硼中心垂直地高于和低于相邻正方形的带负电荷的硼中心。[Et 3 NH]+离子位于阴离子硼中心对之间。静电阴离子-阳离子吸引（图2a）和氢键（图2b）的组合使堆叠的组件对齐以产生管状结构。如图2b所示，所有的N-H矢量都指向同一方向，并与两个配体氧原子形成明显的氢键（N <$H∑∑ O 2.939（4）和3.018（4）<$）。结构中的所有列都是平行的，并如图3所示排列。任何给定手性的柱与四个相反手性的柱接触。管含有无序溶剂，其非常容易去除而不会破坏管状结构（见下文）。这种结构让人想起Ghadiri等人描述的环肽纳米管，[5]其也由氢键结合在一起以产生管状结构的大环堆叠组成。然而，在（Et 3 NH）4 [B4 L4]的本实施例中，阴离子-阳离子吸引力提供了强大的附加管形成影响。在与上述条件类似的条件下反应，但用苄基二乙胺（BzEt 2N）代替三乙胺，得到组成为（BzEt 2NH）4 [B4 L4] Σ 4 MeOH的晶体。[3b晶体结构与溶剂化的（Et 3 NH）4 [B4 L4]非常相似。[B4L4] 4 <$squares，all of the same
Reaction of LH4 with B (OMe) 3 and triethylamine (Et3N) in methanol in a sealed tube at 1608C generates crystals of solvated (Et3NH) 4 [B4L4].[3a, 4a] The crystal structure contains discrete molecular [B4L4] 4¿ squares, shown in Figure 1, in which all four L4¿ units have the same handedness. The B∑∑∑ B separation across the center of the squares is 13.22 ä. The organoborate squares, all of the same chirality, stack one on top of another in the direction perpendicular to the B4 plane (that is, the c direction), with the negatively charged boron centers of one square vertically above and below those of adjacent squares. The [Et3NH]+ ions are located between pairs of anionic boron centers. A combination of electrostatic anion–cation attraction (Figure 2a) and hydrogen bonding (Figure 2b) aligns the components of the stack to produce a tubular structure. As is indicated in Figure 2b, all the N–H vectors point in the same direction and form significant hydrogen bonds to two ligand oxygen atoms (N¿ H∑∑∑ O 2.939 (4) and 3.018 (4) ä).All the columns in the structure are parallel and are packed as shown in Figure 3. Any column of a given chirality makes contact with four columns of opposite chirality. The tubes contain disordered solvent, which is very easily removed without disruption of the tubular structure (see below). This structure is reminiscent of the cyclic peptide nanotubes described by Ghadiri et al.,[5] which also consist of stacks of macrocycles hydrogen bonded together to generate tubular structures. However, in the present example of (Et3NH) 4 [B4L4], anion–cation attraction provides a powerful additional tube-forming influence. Reactions under conditions similar to those above, but with benzyldiethylamine (BzEt2N) replacing triethylamine, yield crystals of composition (BzEt2NH) 4 [B4L4]∑ 4 MeOH.[3b, 4b] The crystal structure is very similar to that of solvated (Et3NH) 4 [B4L4]. Stacks of [B4L4] 4¿ squares, all of the same