catena-Poly[zinc(II)-μ(3)-{hydrogen [1-hydr-oxy-2-(3-pyridinio)ethane-1,1-di-yl]diphospho-nato}].

In the polymeric title compound, [Zn(C(7)H(9)NO(7)P(2))](n), the zinc(II) centre displays a tetra-hedral coordination geometry provided by four O atoms from three different phospho-nate groups. The crystal structure consists of ladder chains parallel to the b axis built up from vertex-sharing of ZnO(4) and PO(3)C tetra-hedra. The chains are linked by strong intra- and inter-chain O-H⋯O and N-H⋯O hydrogen bonds, forming a three-dimensional supra-molecular assembly.