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

TitleExploring the dynamics of calix[4]pyrrole: effect of solvent and fluorine substitution
Publication TypeJournal Article
Year of Publication2007
AuthorsBlas, JR, Lopez-Bes JM, Marquez M, Sessler JL, Luque FJ, Orozco M
JournalChemistry (Weinheim an der Bergstrasse, Germany)
Pagination1108 - 1116
Date Published2007///
KeywordsCalixarenes/chemistry; Fluorine/chemistry; Models, Molecular; Molecular Structure; Porphyrins/chemistry; Solvents/chemistry
AbstractMolecular 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.