Sulfonated 1,3-bis-(4-pyrid-yl)propane.

In the title compound, 4-[3-(3-sulfonato-pyridin-1-ium-4-yl)prop-yl]pyridin-1-ium-3-sulfonate, C(13)H(14)N(2)O(6)S(2), the mol-ecule is zwitterionic, with the sulfonic acid proton transfered to the basic pyridine N atom. Also, the structure adopts a butterfly-like conformation with the sulfonate groups on opposite sides of the 'wings'. The dihedral angle between the two pyridinium rings is 83.