The threading of monostoppered alkylbenzylammonium axles 7+ and 8+ with the calix-wheel 3 can occur by both routes of entering the macrocycle 3 in the cone conformation: passage through the upper rim and the through the lower rim. Thus, under thermodynamic conditions, with both the axles 7+ and 8+, the two possible orientations of calixpseudorotaxane, namely, endo-benzyl and endo-alkyl, are formed by a stereoselectivity controlled by the endo-alkyl rule. Interestingly, by 1H NMR monitoring of the threading process between 8+ and 3, we revealed two calixpseudorotaxane isomers in which the calix-wheel adopts 1,2,3-alternate and cone conformations, which represent the kinetic and thermodynamic species, respectively. Finally, the synthesis of ammonium-based oriented calixrotaxane is here described.
|Titolo:||Threading of an Inherently Directional Calixarene Wheel with Oriented Ammonium Axles|
|Data di pubblicazione:||2017|
|Appare nelle tipologie:||1.1.1 Articolo su rivista con DOI|