A statistical analysis of halide · · · H–A (A = OR, NR2, N+R3) hydrogen bonding interactions in the solid state
Abstract
The interaction between F–, Cl–, Br– and I– and organic H-bond donors OH, NH and N+H are examined in detail using the Cambridge Structural Database. The ammonium group is shown to be the most effective H-bond donor to the halides, followed by the hydroxy group and neutral NH. Comparison of the H-bonding requirements of the anions in each case shows trends in X– · · · HA distances (r), with the Δr interval between F– and Cl– being the greatest, and that between Cl– and Br– the least. Mean H-bonding angles ∠AHX– are ca. 160 ° and tend towards greater linearity with increasing quality of the hydrogen bond. Interactions of halide ions with macrocyclic H-bonding receptors and the potential for host selectivity are discussed.