N,N'-BRIDGED DERIVATIVES OF 2,2'-BIBENZIMIDAZOLE

A series of 2,2'-bibenzimidazolium salts has been prepared by N,N'-bri dging using dihaloalkanes. These salts may be reduced by either one or two electrons to the corresponding cation radical or neutral 2,2'-bib enzimidazolylidene. The latter species undergoes a chemiluminescent re action with dioxygen to afford conformationally unique ureaphanes. Two benzimidazole molecules may be joined by N,N'-bridges to form bis(ben zimidazolium) salts which may be deprotonated with sodium hydride. Sub sequent intramolecular 2,2'-coupling leads to the same 2, 8'-bibenzimi dazolinylidenes. The structural features of the ureaphane oxidation pr oducts have been studied by X-ray crystallography and NMR. An equimola r mixture of a 2,2'-bibenzimidazolium salt and the corresponding 2,2'- bibenzimidazolinylidene will coproportionate to form the analogous cat ion radical.