Abstract Oxidation of substituted N-aminopyridinium compounds yields bipyridinium salts. After anion exchange Br−→ CIO math image, it was possible to grow single crystals from the 4, 4′-di (tert-butyl) derivative. The structure determined at 100 K shows a dihedral angle of 84 between the molecular halves connected by a shortened N [BOND] N bond of 143 pm in length. This result is contrary to that expected from the isoelectronic correspondence〉 C [ ...