Anion Recognition Based on a Combination of Double-Dentate Hydrogen Bond and Double-Side Anion-π Noncovalent Interactions

Anion recognitions between common anions and a novel pincer-like receptor (N,N'-bis(5-fluorobenzoyloxyethyl)urea, BFUR) were theoretically explored, particularly on geometric features of the BFUR@X (X = F^-, Cl^-, Br^-, I^-, CO₃^2-, NO₃^-, and SO₄^2-) systems at a molecular level in this work. Complex structures show that two N-H groups as a claw and two -C₆F₅ rings on BFUR as a pair of tweezers simultaneously interact with captured anions through cooperative double-dentate hydrogen bond and double-side anion-π interactions. The binding energies and thermodynamic information indicate that the recognitions of the seven anions by BFUR in vacuum are enthalpy-driven and entropy-opposed, which occur spontaneously. Although the binding energy ΔE_cp between F^- and BFUR is relatively high (289.30 kJ·mol^-1), ΔE_cp, ΔG, and ΔH of the recognition for CO₃^2- and SO₄^2- are much larger than the cases of F^-, Cl^-, Br^-, I^-, and NO₃^-, suggesting that BFUR is an ideal selective anion receptor for CO₃^2- and SO₄^2-. Additionally, energy decomposition analysis based on localized molecular orbital energy decomposition analysis (LMO-EDA) was performed; electronic properties and behaviors of the present systems were further discussed according to calculations on frontier molecular orbital, UV-vis spectra, total electrostatic potential, and visualized weak interaction regions. The present theoretical exploration of BFUR@X (X = F^-, Cl^-, Br^-, I^-, CO₃^2-, NO₃^-, and SO₄^2-) systems is fundamentally crucial to establish an anion recognition structure-property relationship upon combination of different noncovalent interactions, that is, double-dentate hydrogen bond and double-side anion-π interactions.

Anion binding consistency by influence of aromatic meta-disubstitution of a simple urea receptor: regular entrapment of hydrated halide and oxyanion clusters

Consistent recognition of asymmetric divalent sulphate, hydrated chloride and acetate along with fluoride induced bicarbonate within self-assembly of bis-urea receptor is observed.

Conformations of benzene-based tripodal isatin-bearing compounds in the crystalline state

Studies of molecular conformations, examples of polymorphic forms, new solvates and analysis of supramolecular motifs giving interesting insights into molecular recognition phenomena are reported.

Trimethyl-, triethyl- and trimethoxybenzene-based tripodal compounds bearing pyrazole groups: conformations and halogen-/hydrogen-bond patterns in the crystalline state

X-ray analyses of a series of benzene-based tripodal molecules1–9provide interesting insights into the molecular recognition phenomena and give information about the different conformations which adopt the molecules in the solvent-free crystals and in solvates.