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|Title:||Efficient preparation of separable pseudo[n]rotaxanes by selective threading of oligoalkylammonium salts with cucurbituril|
|Authors:||Yin, J. |
|Source:||Yin, J., Chi, C., Wu, J. (2009-06-08). Efficient preparation of separable pseudo[n]rotaxanes by selective threading of oligoalkylammonium salts with cucurbituril. Chemistry - A European Journal 15 (24) : 6050-6057. ScholarBank@NUS Repository. https://doi.org/10.1002/chem.200900251|
|Abstract:||We describe the efficient preparation of well-defined, homogeneous pseudo[n]rotaxanes (n=2, 3, 4, 5) by the selective threading of oligoalkylammonium salts with cucurbituril (CB) and the subsequent simple separation of the pure pseudo[n]rotaxanes from the complicated system. A series of well-defined oligoalkylammonium salts were prepared by stepwise synthesis and their molecular recognition and self-assembly with a solution of CB in CF3CO2D/D2O (1:1 v/v) were investigated. As a result of the high affinity of CB to the p-xylene diammonium units (-NH 2 +CH2C6H4CH 2NH2 +-) in the oligoalkylammonium salts, the CB rings threaded onto these cationic threads to form pseudorotaxane structures. Interestingly, due to the repulsive dipole-dipole electrostatic interactions between the CB units and steric hindrance, the threading process exhibited a high selectivity and a unique self-assembling mode was discovered in which two CB units cannot bind the same ammonium site. The as-formed well-defined pseudo[n]- rotaxanes can be easily separated as pure compounds from the mixture by simple counterion exchange with NH4PF6 and the pure pseudo[n]rotaxanes are stable and partially soluble in normal organic solvents. Such facile preparation and separation are mainly ascribed to the high binding constant between CB and the oligoalkylammonium salts and the unique solubility of CB in protonic acid. As most pseudorotaxanes reported in the literature exist as a dynamic mixture and their separation is usually difficult, our research represents one good example in which pure pseudo[n]rotaxanes (n= 2, 3, 4, 5) can be obtained by a simple "threading-followed-by- precipitation" method. © 2009 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim.|
|Source Title:||Chemistry - A European Journal|
|Appears in Collections:||Staff Publications|
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