Boron- interactions in two 3-(dihydroxyboryl)-anilinium salts analyzed by crystallographic studies and supported by the noncovalent interactions (NCI) index theoretical approach

In the title compounds, 3-(dihydroxyboryl)anilinium bisulfate monohydrate, C6H9BNO2+center dot HSO4-center dot H2O (I), and 3-(dihydroxyboryl)anilinium methyl sulfate, C6H9BNO2+center dot CH3SO4 (II), the almost planar boronic acid molecules are linked by pairs of O-H center dot center dot center dot O hydrogen bonds, forming centrosymmetric motifs that can be described by the graph-set R-2(2)(8) motif. In both crystals, the B(OH)(2) group acquires a syn-anti conformation (with respect to the H atoms). The presence of the hydrogen-bonding functional groups B(OH)(2), NH3+, HSO4, CH3SO4 and H2O generates three-dimensional hydrogen-bonded networks, in which the bisulfate (HSO4) and methyl sulfate (CH3SO4) counter-ions act as the central building blocks within the crystal structures. Furthermore, in both structures, the packing is stabilized by weak boron(-). interactions, as shown by noncovalent interactions (NCI) index calculations.