Calculate Several Supramolecular Recognition System Simulation

Up to now, there are mainly three host molecules:crown ether, cyclodextrin and calixarene (calixpyrrole) in the field of supramolecular chemistry, which have already been the hot topics one after another. People are interested in their unique feature of molecule recognition and assembling which are applied in biological drugs, catalysis, organic synthesis and so on. In this paper, the process and mechanism of molecule recognition were deeply studied. The main content and results of this paper are as follows:1. The interaction process of calix[4]pyrrole (CP) and eight different anions (F-,Cl-, Br-, H2PO4-, NO3-, CH3COO-, HSO4-, ClO4-) were studied at the B3LYP/cc-pVDZ level. We found that whatever kind of anion it was, hydrogen bonds (N-H…X (X=F, Cl, Br, O)) were the main force to form the complexes. With the electronegativity of X increased, the hydrogen bond became stronger, the complexes became more stable, which are coincide with our own knowledge. Then, NBO (Natural Bond Orbital) analysis, wave function analysis and AIM (Atoms In Molecule) analysis were followed. At last, we compared the stability of these complexes from the aspect of thermodynamics, and we got the stability order:CP-F->CP-CH3COO->CP-Cl->CP-H2PO4->CP-NO3->CP-Br->CP-HSO4->CP-ClO4-.2. On the basis of calix[4]arene, we came up with a new calix-crown host (H). The complexes between H and ion pairs Na+X-(X=F-, Cl-, Br-) were studied using ONIOM (B3LYP/LANL2DZ:PM3) method in gase phase. We found two types of ion pair complexes: host separated and contacted. They had the same stability order:Na+F-/H> Na+CI-/H> Na+Br-7H.Then, the MD (molecular dynamics) method was carried with the Forcite model in Materials Studio5.5software, and the stability of above complexes were studied in water solution and chloroform solution. We found that the host separated complexes were apt to change along with the surroundings. They were stable in the gas phase, and seprated in water solution, while transformed to contacted type in chloroform solution. For contacted complexes, they were stable whatever the solution it was.3. The interaction between β-cyclodextrin and single-tail/double-tail imidazole ion liquids surfactants ([Cgmim]Br and [C8C8im]Br) were studied using MD method. Compared with the relative experiments, we got the similar conclusion. In the complexes, the guest-host ratio is1:1for the single-tail surfactant, while1:1and1:2for the double-tail one. When complexed with the single-tail surfactant, the guest used imidazole ring to close to the larger rim of P-cyclodextrin. When complexed with the double-tail one, there were many ways of complexing between host and guest. The guest used two tails to close to the larger rim of β-cyclodextrin at the same time or only one tail close to the β-cyclodextrin. The hydrogen bond between imidazole ring and cyclodedtrin’s rim and hydrophobic interaction between tails and cyclodedtrin’s cavity were the main facters that make the complexes stable.