N-bridged heterocycles. Part II. Synthesis and aromaticity of 1,3-polymethylene-benzimidazolium salts {[n](1,3)benzimidazolophanium salts}, -benzimidazolones, and -benzimidazolethiones

Abstract

[n](1,3)Benzimidazolophanium salts have been synthesised from NN′-polymethylene-o-phenylenediamines with 6–12 methylene groups in the bridge, by the action of dichloromethyl methyl ether. The aromaticity of this series of compounds is compared to that of the corresponding series of benzimidazol-ones and -thiones with 5–12 bridging methylene groups by a study of their u.v., i.r., and ¹H and ¹³C n.m.r. spectra. It is concluded that aromaticity is significant in the salts with n 6, in the bridged benzimidazolones with n 7, and in the bridged benzimidazolethiones with n 7 or 8.