Tetraprotonated Tetra(2-pyridyl)pyrazine: Pyrazine-2,3,5,6-tetra(2-pyridinium) Tetrachloride Dihydrate

In the tetraprotonated form of tetra(2-pyridyl)pyrazine, [C₂₄H₂₀N₆]⁴⁺·4Cl⁻.2H₂O, all four pyridine groups are protonated. The structure possesses a crystallographic center of symmetry. The four pyridinium H-atoms are hydrogen bonded to two Cl⁻ anions, forming NH...Cl...HN units. In the crystal, two more Cl⁻ anions and two water molecules of crystallization form a hydrogen-bonded chain that threads its way through the tetra-cations.

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