The Host-Guest Chemistry Based On Crown Ethers Derivatives And Secondary Dialkylammonium Salts

The study of host-guest chemistry based on crown ethers and secondary dialkylammonium salts is an important part in supramolecular chemistry.For a long time,it has been widely accepted that a macrocycle needs at least 24 C,N,O or S atoms for the threading of an alkyl group into its cavity.How big a macrocycle should be for threading to occur is a basic and important question in threaded structure chemistry.This thesis included three parts:(1)The study of the complexation and threaded structures based on the benzo-21-crown-7/secondary dialkylammonium salt recognition motif;(2)Secondary dialkylammonium salt can thread through the cavity of pyrido-21-crown-7 to form the threaded structures;(3)The study of the size of macrocycle rings which can complex with secondary dialkylammonium salts.The research results were summarized as follow:1.In acetone solution benzo-21-crown-7 can complex with secondary dialkylammonium salts(such as di-n-butylammonium hexafluorophosphate, benzyl-n-butylammonium hexafluorophosphate,o-benzonitrile-n-butylammonium hexafluorophosphate etc.)to form pseudorotaxanes,which are slow-exchange systems.We successfully prepared[2]rotaxane based on the new recognition motif using two phenyl groups as the stoppers.We can find the good size fit between the host and guest by X-ray study.2.It is demonstrated that P21C7 can bind secondary dialkylammonium salts stronger than B21C7 in solution.Moreover,P21C7 is proved to be able to be employed in the template-directed synthesis of a[2]rotaxane-type threaded structure as confirmed by proton NMR spectroscopy,electrospray ionization mass spectrometry and single crystal X-ray analysis.3.We has also investigated the size of macrocycle rings which can complex with secondary dialkylammonium salts.DB20C6 and DB21C7 can not complex with secondary dialkylammonium salts in acetone solution,Therefore,B21C7 is the smallest benzocrown ether which is capable of forming threaded structures with secondary dialkylammonium salts. Complexations of DB22C7,DB23C7,DB24C8 with secondary ammonium salts were found to be fast-exchange systems.We tried to prepared[2]rotaxane based on DB22C7 using two phenyl groups as the stoppers to get a product which is a rotaxane in CDCl₃,however, the dumbbell-shaped component can get out of the cavity of DB22C7 in the highly polar solvent such as DMSO.The system is just a rotaxane-like camplex.