A supramolecular assembly containing an unusually short n-h…n hydrogen bond - an x-ray and neutron diffraction study

A supramolecular assembly formed between phthalimide and 2-guanidinobenzimidazole, containing a short 2.692(4)AR N-H…N hydrogen bond, is reported. The crystal structure of this species was determined by both X-ray and neutron diffraction. The diffraction data reveal that the proton involved in the short hydrogen bond has been transferred from the phthalimide to the guanidinobenzimidazole to form an ion pair. There is also an interesting stacking interaction between the atoms involved in the short hydrogen bond and the π system of a phthalimide molecule that is approximately 3.3 A away. The structure is compared with the structure of a similar assembly formed between 4-nitrophthalimide and 2-guanidinobenzimidazole.