Bis(4-carbamoylpiperidinium) biphenyl-4,4′-disulfonate

In the title isonipecotamide salt ₂C₆H ₁₃N₂O⁺·C₁₂H₈O ₆S₂^2-, the asymmetric unit comprises one biphenyl-4,4′-disulfonate dianion which lies across a crystallographic inversion centre and another in a general position [dihedral angle between the two phenyl rings is 37.1 (1)°], together with three isonipecotamide cations. Two of these cations give a cyclic homomeric amide-amide dimer inter-action [graph set R₂²(8)], the other giving a similar dimeric inter-action but across an inversion centre, both dimers then forming lateral cyclic R₄²(8) pyrimidinium-amide N - H⋯O inter-actions. These units are linked both laterally and longitudinally to the sulfonate groups of the dianions through piperidinium N - H⋯O hydrogen bonds, giving a three-dimensional framework structure.