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

摘要

A series of 2,2'-bibenzimidazolium salts has been prepared by N,N'-bridging using dihaloalkanes. These salts may be reduced by either one or two electrons to the corresponding cation radical or neutral 2,2'-bibenzimidazolylidene. The latter species undergoes a chemiluminescent reaction with dioxygen to afford conformationally unique ureaphanes. Two benzimidazole molecules may be joined by N,N'-bridges to form bis(benzimidazolium) salts which may be deprotonated with sodium hydride. Subsequent intramolecular 2,2'-coupling leads to the same 2, 8'-bibenzimidazolinylidenes. The structural features of the ureaphane oxidation products have been studied by X-ray crystallography and NMR. An equimolar mixture of a 2,2'-bibenzimidazolium salt and the corresponding 2,2'-bibenzimidazolinylidene will coproportionate to form the analogous cation radical. [References: 23]