Charge-Assisted Complexation of Anions of Different Dimensionality by Benzimidazole-Based Receptors Bearing -OH Functionality

Two benzimidazole-based receptors (L1 and
L2) bearing -OH functionality form crystalline salts with
different organic and inorganic acids viz. [L1H+]­[Cl–] (1), [L1H+]­[NO3–] (2), [L1H+]­[OAc–] (3), [L1H+]­[DNB–]·DMF (4),
[L1H+]­[H2PO4–] (5), [L2H+]­[OAc–]·AcOH (6), [L2H+]­[DNB–] (7), and [L2H+]­[HSO4–]·H2O (8) where the shape of the counteranion drives the solid structure
from a one-dimensional polymeric chain to a three-dimensional structure.
Structural analyses show that the anion binding in all eight complexes
is attributable entirely to NH+···anion, NH···anion, OH···anion, and multiple CH···anion hydrogen
bonding interactions. In the solid structure the planar nitrate anion
forms a cyclic structure with receptor L1, whereas the
acetate anion with the same receptor leads to a molecular barrel type
structure. Again the tetrahedral dihydrogen
phosphate anion forms a polymeric interanionic chain structure with
L1, and the other tetrahedral hydrogen sulfate anion forms
hydrogen sulfate–(water)2–hydrogen sulfate
adducts with charged L2.