Computational insights into halide recognition by dipodal cleft receptors based on <i>m</i> -xylyl frameworks functionalised with urea and thiourea moieties

The recognition of halide anions by synthetic receptors is of fundamental importance in supramolecular chemistry due to the wide relevance of anions in biological and environmental systems. In this work, halide binding by two dipodal cleft receptors based on m-xylyl frameworks functionalised with urea and thiourea moieties is investigated using density functional theory. The full halide series (F−, Cl−, Br−, and I−) is considered to analyse intrinsic affinity and selectivity trends. Gas-phase calculations of interaction and stabilisation energies show a consistent binding order, with fluoride exhibiting the strongest and iodide the weakest interaction. The nature of host–guest interactions is examined using QTAIM, NBO, NCI-RDG, and EDA-NOCV analyses, revealing the relative contributions of electrostatic, orbital, and dispersive effects. Solvent effects are evaluated to assess their influence on complex stability. The computed thermodynamic parameters in solution reproduce experimental binding trends and show very good agreement with reported formation constants.