Four new supramolecular coordination complexes and salts based on proton-transferred pyridine-2,6-dicarboxylic acid N-oxide formulated as (Htata)(Hpydco)·H2O (1), (Htata)2(pydco)·2H2O (2), (H9a-acr)2[Zn(pydco)2(H2O)2]·4H2O (3), and (H9a-acr)2[Co(pydco)2(H2O)2]·4H2O (4) (where H2pydco = pyridine-2,6-dicarboxylic acid N-oxide, tata = 2,4,6-triamino-1,3,5-triazine (melamine) and 9a-acr = 9-aminoacridine) have been synthesized by proton transfer from H2pydco as ligand and to tata and 9a-acr. The structures of 1–4 were characterized by elemental analysis, infrared spectroscopy, and single crystal X-ray diffraction methods. Compounds 1 and 2 are salts of proton-transferred H2pydco and melamine with two separate formulas. There is a difference between the anionic fragment in 1 and 2, the anionic part of 1 retains one acid proton (Hpydco−) which is involved in a strong, intramolecular hydrogen bonding with the oxygen attached to nitrogen, while the acid units in 2 are fully deprotonated (pydco2−). The linear chains of melaminium cations with an anionic motif and water molecules lead to 2-D zipper layers in 1 and 2-D zigzag layers in 2. These layers are held together via an extensive network of hydrogen bonds, π+–π + stacking, N+–H⋯π+, and lp⋯π+ interactions to extend the structures into the 3-D supramolecular framework. Single-crystal studies revealed that 3 and 4 are isostructural with distorted octahedral geometry about the metal consisting of two pydco2− ligands acting in bidentate fashion and two trans-disposed water molecules. They also adopt alternating cationic and anionic layers with 9-aminoacridinium cations and transition metal complex anions which are linked to each other by a variety of noncovalent interactions such as ion pairing, hydrogen bonding and π–π stacking.

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