Poly[[(4,4′-bipyridine-κN)[μ(3)-(S)-2-hy­droxy­butane­dioato-κ(4) O (1),O (2):O (4):O (4′)]zinc] dihydrate]

In the title compound, {[Zn(C(4)H(4)O(5))(C(10)H(8)N(2))]·2H(2)O}(n), the Zn(II) ion displays a distorted tetra­gonal–pyramidal coordination environment with one hy­droxy O and three carboxyl­ate O atoms from three malate anions, and the one remaining position occupied by an N atom from a 4,4′-bipyridine ligand. The pyridine rings of the 4,4′-bipyridine ligand are twisted with respect to each other by a dihedral angle of 35.8 (2)°. The uncoordinated water mol­ecules are linked to the complex mol­ecules by O—H⋯O hydrogen bonds. Each malate anion forms four coordination bonds with three Zn atoms, establishing a layer structure parallel to the ac plane. Adjacent layers are further linked via O—H⋯N hydrogen bonding. π–π stacking between the pyridine rings [face-to-face distance = 3.651 (3) Å] occurs in the crystal structure.