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Exploring the Dynamics of Calix[4]pyrrole: Effect of Solvent and Fluorine Substitution
Author(s) -
Blas J. Ramón,
LópezBes Jose Maria,
Márquez Manuel,
Sessler Jonathan L.,
Luque F. Javier,
Orozco Modesto
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200600757
Subject(s) - chemistry , pyrrole , conformational isomerism , solvent , hydrogen bond , molecular dynamics , molecule , fluorine , ion , crystallography , computational chemistry , fluoride , stereochemistry , organic chemistry , inorganic chemistry
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.