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

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.