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Hydrogen‐Bonding‐Mediated Dynamic Covalent Synthesis of Macrocycles and Capsules: New Receptors for Aliphatic Ammonium Ions and the Formation of Pseudo[3]rotaxanes
Author(s) -
Xu XiaoNa,
Wang Lu,
Wang GuiTao,
Lin JianBin,
Li GuangYu,
Jiang XiKui,
Li ZhanTing
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200900309
Subject(s) - imine , hydrogen bond , intramolecular force , covalent bond , chemistry , dynamic covalent chemistry , monomer , amide , trifluoroacetic acid , polymer chemistry , aldehyde , rotaxane , hydrazone , self assembly , linker , supramolecular chemistry , combinatorial chemistry , organic chemistry , molecule , polymer , catalysis , computer science , operating system
Dynamic covalent synthesis! Intramolecular hydrogen‐bonding induces amino‐ and aldehyde‐appended aryl amides to adopt a rigid “V”‐shaped conformation. As a result, stable two‐layered capsules can be assembled quantitatively through the one‐step formation of six imine bonds. The new capsules form complexes with aliphatic diammonium ions to give unique two‐layered pseudo[3]rotaxanes (see figure).This paper describes a novel, highly efficient approach to the self‐assembly of monomacrocycles and two‐layered capsules by using dynamic covalent chemistry. Intramolecular hydrogen‐bonding was used to preorganize aromatic amide‐based monomers that contain aldehyde and tert ‐butoxycarbonylamino units. As a result, in the presence of an excess of trifluoroacetic acid (TFA), four monomers could self‐couple to produce macrocycles selectively through the formation of three imine or hydrazone bonds. Three dipodal precursors were also prepared by connecting two hydrogen‐bonded segments with a flexible linker. In the presence of TFA, these precursors could also self‐couple, leading to the exclusive formation of two‐layered capsules. As a result of intramolecular hydrogen‐bonding, all the macrocycles and capsules were stable in solution and could be purified by simple recrystallization. The new capsules were able to form complexes with linear propylenediammonium derivatives to give unique two‐layered pseudo[3]rotaxanes.