Exploring the dynamics of calixpyrrole: effect of solvent and fluorine substitution.
|Exploring the dynamics of calixpyrrole: effect of solvent and fluorine substitution.
|Year of Publication
|J Blas, Ramón, López-Bes Jose Maria, Márquez Manuel, Sessler Jonathan L., F Luque Javier, and Orozco Modesto
|Calixarenes, Fluorine, Models, Molecular, Molecular Structure, Porphyrins, Solvents
Molecular dynamics simulations show that calixpyrrole (CP) and octafluorocalixpyrrole (8F-CP) are extremely flexible molecules. CP mainly adopts the 1,3-alternate conformation in all the solvents, although the percentage of alternative conformations increases in polar solvents, especially those with good hydrogen-bonding acceptor properties. However, in the case of 8F-CP, the cone conformation is the most populated in some solvents. Transitions between conformers are common and fast, and both CP and 8F-CP can adopt the cone conformation needed for optimum interaction with anions more easily than would be predicted on the basis of previous gas-phase calculations. Furthermore, the present studies show that when a fluoride anion is specifically placed initially in close proximity to CP and 8F-CP in their respective 1,3-alternate conformations, an extremely fast change to the cone conformation is observed in both cases. The results suggest that preorganization does not represent a major impediment to anion-binding for either CP or 8F-CP, and that ion-induced conformational changes can follow different mechanisms depending on the solvent and the chemical substituents present on the calixpyrrole beta-pyrrolic positions.