Crystal structure of zwitterionic bisimidazolium sulfonates

Crystal structures of three zwitterionic bisimidazolium salts 1–3 in which imidazolium sulfonate moieties were connected with aromatic linkers, p-xylylene, 4,4′-dimethylenebiphenyl, and phenylene, respectively, were examined. The latter two were obtained as hydrates. An S-shaped molecular structure in which the sulfonate moiety was placed on the imidazolium ring was observed for 1. A helical array of hydrated water molecules was obtained for 2 while a linear array of hydrated water molecules was observed for 3.