Diaqua-(5-carb-oxy-benzene-1,3-dicarboxyl-ato-κO(1))[8-ethyl-5-oxo-2-(piperazin-4-ium-1-yl)-5,8-dihydro-pyrido[2,3-d]pyrimidine-6-carboxyl-ato-κ(2)O(5),O(6)]zinc monohydrate.

In the title compound, [Zn(C(14)H(17)N(5)O(3))(C(9)H(4)O(6))(H(2)O)(2)]·H(2)O, the complex mol-ecule exists in a zwitterionic form. The Zn(II) ion exhibits a distorted tetra-gonal-pyramidal geometry, being coordinated by two O atoms from the zwitterionic 8-ethyl-5-oxo-2-(piperazin-4-ium-1-yl)-5,8-dihydro-pyrido[2,3-d]pyrimidine-6-carboxyl-ate (L) ligand, one O atom from the 5-carb-oxy-benzene-1,3-dicarboxyl-ate dianion, [Hbtc](2-), and two O atoms from two aqua ligands. In the crystal, N-H⋯O and O-H⋯O hydrogen bonds link the components into a three-dimensional structure. The crystal packing exhibits π-π inter-actions between the aromatic rings, with centroid-centroid distances in the range 3.466 (3)-3.667 (3) Å.