Influence of guests and protonation on the conformation of N,N′-dipyridyl-bis-aza-18-crown-6

Crystallisation of the sodium perchlorate adduct of N,N′-dipyridyl-bis-aza-18-crown-6 from acidic aqueous conditions yielded [(H3O)(N,N′-dipyridyl-bis-aza-18-crown-6)][ClO4] and [Na·N,N′-dipyridyl-bis-aza-18-crown-6]2 [(H+)2N,N′-dipyridyl-bis-aza-18-crown-6][ClO4]4·2H2O. The conformations of crown ethers were significantly influenced by incorporation of an H3O+ or sodium ion, or protonation of the amino nitrogen atoms resulting in three different structures for the macrocycle.