Doubly interpenetrating stereoisomeric three-dimensional frameworks of tripodal neodymium(III) complexes from potentially spacer-controlled enantioselective self-assembly
作者:Cheng-Yong Su、Bei-Sheng Kang、Qing-Chuan Yang、Thomas C. W. Mak
DOI:10.1039/b001236j
日期:——
Two three-dimensional frameworks composed of doubly interpenetrating networks of the same topology but different stereoisomeric structures have been constructed from self-assembly of the chiral building block, Δ- or Λ-[Nd(ntb)2]3+, with different spacers bipy and bpen (ntb = tris(2-benzimidazolylmethyl)amine, bipy = 4,4′-bipyridyl, bpen = trans-1,2-bis(4-pyridyl)ethylene). In the crystal structure of [Nd(ntb)2][ClO4]3·3bipy·2H2O the spacer bipy connects [Nd(ntb)2]3+ cations of the same handedness to generate a chiral network Δ3-Δ . . . (or Λ3-Λ . . .)[Nd(ntb)2]3+· 3bipy}∞, which is interpenetrated further by another identical network. The crystal structure of [Nd(ntb)2][ClO4]3· 3bpen·H2O shows a topologically similar but achiral framework in which each spacer bpen connects either cations of the same chirality or a pair of enantiomers, thus generating a three-dimensional racemate Δ2Λ-Λ . . . (or Λ2Δ-Δ . . .)[Nd(ntb)2]3+·3bpen}∞. Aggregation of the molecular species is effected by N–H⋯N hydrogen bonds, and the observed enantioselective self-assembly can be rationalized by π⋯π interactions between aromatic rings.
使用手性构筑单元Δ型或Λ型[Nd(ntb)2]3+与两种不同的连接配体bipy和bpen(ntb = 三(2-苯并咪唑基甲基)胺, bipy = 4,4′-联吡啶, bpen = 反式-1,2-双(4-吡啶基)乙烯)通过自组装构筑了由相同拓扑结构但不同立体异构结构组成的双重互穿三维框架。在[Nd(ntb)2][ClO4]3·3bipy·2H2O的晶体结构中,连接配体bipy将相同手性的[Nd(ntb)2]3+阳离子相连形成了手性网格Δ3-Δ...(或Λ3-Λ...) [Nd(ntb)2]3+·3bipy}∞,该手性网格进一步与另外一个相同的手性网格互穿。[Nd(ntb)2][ClO4]3·3bpen·H2O的晶体结构表明,所构筑的网格在拓扑结构上与前者是相似的但非手性的,在这个结构中,每个连接配体bpen连接了或者是同手性的或者是两个相反手性的阳离子,从而形成了一个三维的外消旋体网格Δ2Λ-Λ... (或Λ2Δ-Δ...) [Nd(ntb)2]3+·3bpen}∞。分子物种通过N–H…N氢键的作用进行聚集,观察到的手性选择性自组装可以通过芳香环之间的π…π相互作用来解释。