Fluorine versus Hydroxyl in Supramolecular Space: Effect of Organic Fluorine in Molecular Conformation, Lattice Cohesive Energies, and Receptor Binding in a Series of α-Fluoroketones

Abstract

We examine the effect of organic fluorine in the molecular conformation and supramolecular packing in a series of α-fluoroketones in comparison to the analogous α-hydroxyketones. Crystal structures of a series of seven α-fluoroketone analogues have been analyzed using single-crystal XRD, and their crystal-packing features have been investigated using a variety of computational tools. Analysis of molecular conformations in this series of α-fluoroketone structures, along with conformational energy scans, revealed a preference for a near-antiperiplanar conformation for α-fluoroketones as opposed to a syn conformation in their α-hydroxy analogues. A quantitative analysis of intermolecular interaction motifs such as C–H···F, C–H···O, C–H···π, C–F···π, etc. in terms of interaction energies and electron density topological parameters from a QTAIM (quantum theory of atoms in molecules) approach reveal their relative strengths and distance dependence. Electron localization function (ELF) and deformation density maps bring out the electrostatic nature of weak interactions involving organic fluorine. Lattice energy values estimated using the CE-B3LYP method show dominant contributions from dispersion in all these structures, which are around 3–4-fold higher than the electrostatic contribution. While the lattice energy values of the α-fluoroketones are found to be lower than those of their hydroxy analogues, a molecular docking study with a common protein receptor site reveals comparable docking scores for α-fluoroketones with respect to the analogous α-hydroxyketones.