title: 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.
authors.affiliation: Molecular Modeling and Bioinformatics Unit, Institut de Recerca Biomèdica, Parc Científic de Barcelona, Josep Samitier 1-5, Barcelona 08028, Spain.
authors.forename: J Ramón
authors.initials: JR
authors.lastname: Blas
authors.forename: Jose Maria
authors.initials: JM
authors.lastname: López-Bes
authors.forename: Manuel
authors.initials: M
authors.lastname: Márquez
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Sessler
authors.forename: F Javier
authors.initials: FJ
authors.lastname: Luque
authors.forename: Modesto
authors.initials: M
authors.lastname: Orozco
mesh_terms: D047250:Calixarenes / Q000737:chemistry*; D005461:Fluorine / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D011166:Porphyrins / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry*
chemical_list: D011166:Porphyrins; D012997:Solvents; C469811:calix(4)pyrrole; D047250:Calixarenes; D005461:Fluorine