Two novel cadmium and one calcium complex, in which pyridine-2,3-dicarboxylic acid (2,3pydcH 2 ) acts as a monodicarboxylate anion (2,3pydcH) with one acid hydrogen on the hetero-nitrogen or a doubly deprotonated dicarboxylate anion (2,3pydc), have been synthesized and characterized using single crystal X-ray diffraction, elemental analysis and IR, Raman, 1 H and 13 C NMR spectroscopies: [Cd(2,3pydcH) 3 ][Cd(H 2 O) 6 ] 0.5 (1), [Cd(2,3pydc)(H 2 O) 3 ] n (2), [Ca(2,3pydcH) 2 (H 2 O) 3 ] n (3). Complex 1 crystallizes in the trigonal system space group P3¯. The cadmium anion Cd(1) {CdN 3 O 3 } and cation Cd(2) (coordinated by 6 water molecules) possess the same coordination polyhedra (octahedral). Packing analysis reveals that complex 2 (space group Pca2 1 ) has a very interesting coordination network. The column of 2 1 symmetry is built up of translationally repeated mer units, [–O–Cd(3H 2 O)C 7 NO 3 –O–] n , arranged into two dimers rotated relative to each other by 180° (a twisted zigzag screen). Polymeric complex 3 crystallizes in the monoclinic system (space group P2 1 /c). Two molecules of ligand and three molecules of water are bounded directly to the metal ion to give a {CaNO 7 } chromophore, which results in coordination polyhedron described as a pseudo-dodecahedron. It is worth noticing that two types of coordination modes of the 2,3pydcH ligand exist in the structure: one of them acts as chelating (N,O) bidentate ligand in which the carboxyl groups are bound to each other by a very short strong hydrogen bond (O(9)⋯O(12)); the other acts as tridentate (O, O, O′) coordinating anion with one acid hydrogen attached to the nitrogen atom.