冠醚类化合物识别碱金属的理论分析-物理化学专业论文.docxVIP

Abstract Abstract For the separation of a particular alkali metal ion, membrane transport using a crown ether derivative is a convenient, effective, and low-energy-consuming method. In supramolecular chemistry, the appealing crown ethers as a synthesis of macrocyclic host are easy to be prepared. They display a unique charm especially in the recognition of cations and neutral molecules. The paper applied the quantum chemistry mothods and systematically studied the following four systems: (1) The molecular recognition of the N- butyl-aza-15-crown-5 ethers and the alkali metal cations: Li+ and Na+; (2) The molecular recognition of the bis-3-benzo-crown ethers and the alkali metal cations: Na+, K+, Rb+ and Cs+; (3) The molecular recognition of crown ether-bridged Z-stilbenes with alkali metal cations: Li+, Na+, K+, Rb+ and Cs+; (4) The fluorescent molecular devices bearing stilbene-4. Firstly, a series of lariat crown ether based on N-butyl-aza-15-crown-5, which have the same parent macrocycle but with a different terminal group in sidearm, have been calculated at the DFT//B3LYP/6-31G* level in Gaussian 03 package program. The optimized geometries of two conformers (“V”-shaped sandwich conformer A and the linear structural conformer B) for their cation complex are obtained from theory in gas phase. In addition, the NBO analysis and the IR spectra indicate the interaction between the host-guest molecules in detail. As a result, a discrepant conclusion obtained that the main interaction between the LCEs and cations (Li+ and Na+) is the cation-dipole, and the cation-π is negligible in gas phase. Secondly, the binding interactions of bis-3-benzo-15-crown-5 ethers and bis-3-benzo-18-crown-6 ethers (neutral hosts) with series of alkali metal cations Na+, K+, Rb+ and Cs+ (charged guests) have been investigated using quantum chemical density functional theory (DFT). Different optimized structures, binding energies and various thermodynamic parameters of free crow