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, CO, NO, and SO) systems at a molecular level in this work. Complex structures show that two N-H groups as a claw and two -CF 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 between F and BFUR is relatively high (289.30 kJ·mol), ΔE, ΔG, and ΔH of the recognition for CO and SO are much larger than the cases of F, Cl, Br, I, and NO, suggesting that BFUR is an ideal selective anion receptor for CO and SO. 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, CO, NO, and SO) 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.