Exploring the dynamics of calix[4]pyrrole: effect of solvent and fluorine substitution.

Abstract

Molecular dynamics simulations show that calix[4]pyrrole (CP) and octafluorocalix[4]pyrrole (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 calix[4]pyrrole beta-pyrrolic positions.

Cite this paper

@article{Blas2007ExploringTD, title={Exploring the dynamics of calix[4]pyrrole: effect of solvent and fluorine substitution.}, author={Jos{\'e} Ram{\'o}n Blas and Jose Mar{\'i}a L{\'o}pez-Bes and Manuel Lozano M{\'a}rquez and Jonathan L Sessler and F. Javier Luque and Modesto Orozco}, journal={Chemistry}, year={2007}, volume={13 4}, pages={1108-16} }