2,6-Dihy­droxy-4-oxo-2-(pyridin-1-ium-3-yl)-4H-1,3,2-benzodioxaborinin-2-ide 0.67-hydrate

The asymmetric unit of the title compound, C(12)H(10)BNO(5)·0.67H(2)O, contains three independent pyridinylboronic acid esters adopting zwitterionic forms and two water mol­ecules. The six-membered heterocyclic rings in the boronic esters have half-chair conformations and the deviations of the B atoms from the boronate mean planes range from 0.456 (3) to 0.657 (3) Å. All of the B atoms have tetra­hedral coordination environments, with B—O and B—C bond lengths of 1.446 (4)–1.539 (3) and 1.590 (5)–1.609 (5) Å, respectively. In the crystal, the ester and water mol­ecules are linked into a three-dimensional network by a large number of O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds. The crystal packing is further accomplished by π–π inter­actions, with centroid–centroid distances of 3.621 (4)–3.787 (4) Å.