Methylazacalixpyridines: Remarkable bridging nitrogen-tuned conformations and cavities with unique recognition properties
Methylazacalixpyridines: Remarkable bridging nitrogen-tuned conformations and cavities with unique recognition properties
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甲基氮杂花吡啶：具有独特识别特性的显着桥接氮调节构象和空腔
DOI：
10.1002/chem.200600377
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发表时间：
2006-12-13
影响因子：
4.3
通讯作者：
Wang, Mei-Xiang
中科院分区：
文献类型：
--
作者：
Gong, Han-Yuan;Zhang, Xiao-Hang;Wang, Mei-Xiang
以2，6-二溴吡啶、2，6-二氨基吡啶和苯-1，3-二胺为原料，通过一种简便的片段偶联方法合成了甲基氮杂杯[n]吡啶(n=4，8)和甲基氮杂杯[m]芳烃[n]吡啶(m=n=2，4)。由于氮的固有电子性质，它可以主要采用杂交，允许它与相邻的一个或两个吡啶环进行不同程度的共轭、部分共轭或不共轭，所得到的氮桥联杯氧吡啶衍生物作为一类独特的大环主体分子，具有有趣的构象结构，提供了可微调的空腔和多种识别性能。在溶液中它是流动的，而在固体状态下，甲基氮杂杯[4]吡啶采用1，3-交替构象，具有C，对称性，其中每两个桥氮原子与一个吡啶环共轭。质子化后，甲基氮杂杯[4]吡啶物种的四个桥氮原子具有不同的共轭体系，得到类似的扭曲的1，3-交替构象，具有近似的S对称性。然而，每个质子化的甲基氮杂杯[4]吡啶的空腔都有细微的变化，以适应不同大小和几何形状的客体物种，如平面DMF或HO2CCO2-离子，扭曲的HO2CCO2-离子，以及四面体ClO4-离子。作为大环主体，甲基氮杂杯[8]吡啶和甲基氮杂杯[4]芳烃[4]吡啶都通过范德华作用力与富勒烯C-60和C-70有效地相互作用。它们的容易制备、多样的构象结构和识别性能使这些含有多氮的杯芳烃或环芳烃成为超分子化学中独特和强大的大环主体。
Methylazacalix[n]pyridines (n = 4, 8) and methylazacalix [m] arene[n]pyridines (m = n = 2, 4) have been synthesized by a convenient fragment coupling approach starting from 2,6-dibromopyridine, 2,6-diaminopyridine, and benzene-1,3-diamine. Thanks to the intrinsic electronic nature of nitrogen, which can adopt mainly hybridization, allowing it variously to conjugate, partially conjugate, or not conjugate with the adjacent one or two pyridine rings, the resulting nitrogen-bridged calixpyridine derivatives act as a unique class of macrocyclic host molecules with intriguing conformational structures offering fine-tunable cavities and versatile recognition properties. Whilst in solution it is fluxional, in the solid state methylazacalix[4]pyridine adopts a 1,3-alternate conformation with a C,, symmetry in which every two bridging nitrogen atoms conjugate with one pyridine ring. After protonation, the methylazacalix[4]pyridinium species has a different conjugation system of its four bridging nitrogen atoms, yielding the similar twisted 1,3-alternate conformations with an approximate S, symmetry. The cavity of each protonated methylazacalix[4]pyridine, however, varies finely to accommodate guest species of different size and geometry, such as planar DMF or HO2CCO2- ion, a twisted HO2CCO2- ion, and a tetrahedral ClO4- ion. As giant macrocyclic hosts, both methylazacalix[8]pyridine and methylazacalix[4]arene[4]pyridine interact efficiently with fullerenes C-60 and C-70 through van der Waals forces. Their ease of preparation, versatile conformational structures, and recognition properties make these multinitrogen-containing calixarenes or cyclophanes unique and powerful macrocyclic hosts in supramolecular chemistry.