Bis(2,4'-bipyridin-1'-ium) 2,5-dicarboxy­benzene-1,4-carboxyl­ate benzene-1,2,4,5-tetra­carboxylic acid

The title organic salt, 2C₁₀H₉N₂⁺·C₁₀H₄O₈^2-·C₁₀H₆O₈ or 2(H-2,4'bpy)(H₂bta)·H₄bta (where H-2,4'bpy is the 2,4'-bipyridine cation, H₂bta is the 2,5-dicarboxy­benzene-1,4-carboxyl­ate anion and H₄bta is the benzene-1,2,4,5-tetra­carboxylic acid mol­ecule), crystallizes with both the H₂bta dianion and the H₄bta mol­ecule lying about inversion centres in the triclinic unit cell. This organic salt is formed by an extensive and complex hydrogen-bonding network containing both homo- and heteronuclear neutral and ionic inter­actions.