The Host-Guest Chemistry Based On The Host Compounds Of Crown Ethers Derivatives

The study of host-guest chemistry based on crown ethers and their derivatives isan important part of supramolecular chemistry. The intermolecular weak forces, suchas Vander Waals forces, hydrogen bonding,π-πstacking and so on, exit in mosthost-guest systems based on crown ethers and their derivatives. The study on thenon-covalent bonding in supramolecular chemistry should be helpful forunderstanding of basic life phenomena such as the catalysis of enzyme.This thesis included two parts: (1) synthesis and characterizations of hostcompounds based on bis(m-phenylene)-32-crown-10, for example, cryptand, andguest compounds containing electron-deficient aromatic groups, such as paraquat andN, N'-dimethyl-2, 7-diazapyrenium bis(hexafluorophosphate); (2) the study of thecomplexation and the intermolecular weak forces in these host-guest systems via ~1HNMR, fluorescence and X-ray study etc. The research results were summarized asfollow:1. In solution, such as acetonitrile and acetone, host compounds,bis(m-phenylene)-32-crown-10 and derivatives (for example, cryptands) did well inmolecular recognization and self assembly with guest compounds containingelectron-deficient group, such as paraquat. Hydrogen bonding, change transfer andπ-πstacking of interaction are main driving forces for the formation of thesecomplexes.2. By comparing the association constants (K_a) and chemical shift changesbefore and after complexation for complexs of one guest compound (N, N'-dimethyl-2,7-diazapyrenium bis (hexafluorophosphate) with different host compounds, it wasfound that the value of K_a increases in different degrees when host compounds aresubstituted bis(m-phenylene)-32-crown-10 and cryptands. Especially for cryptands,the value of K_a increases up to 100 folds. The trend was consistent with previousreports.3. By comparing K_a, the chemical shift changes and crystal structures for the complexes composed of two kinds of cryptands and two kinds of guest compounds (N,N'-dimethyl-2, 7-diazapyrenium bis(hexafluorophosphate), N, N'-dimethyl 4,4'-bi-pyridinium bis(hexafluorophosphate), it was found the intermolecular forces would beaffected by size fit and electronic density of the host and guest compounds.