Electronic nature of substituents and the structure of 4,4′-dipyridylium dications: Crystal structure of N, N′-di(2-carboxyethyl)-4,4′-dipyridylium diperchlorate

The crystal structure of N,N′-di(2-carboxyethyl)-4,4′-dipyridylium diperchlorate, C16H18Cl2N2O12, is determined using X-ray diffraction analysis at 293 K. The crystals are orthorhombic, a = 20.084(4) Å, b = 8.687(2) Å, c = 11.725(2) Å, space group Pna21, and Z = 4; 1688 reflections measured; and R = 0.056 and Rw = 0.059 for 1244 reflections with I > 3σ(I). It is found that, in the absence of charge transfer or short intramolecular O⋯N contacts, the nucleus of the dication adopts a twist conformation (the angle of rotation between the planes of the pyridine rings is equal to 23°).