Bridged Derivatives of 2,2'-Biimidazole

Article abstract of DOI:10.1021/jo00274a019

The reaction of 2,2'-biimidazole with 1,n-dihaloalkanes or o-xylylene dibromide leads to a series of N,N'-bridged derivatives.When these substances are treated with a second equivalent of 1,n-dihaloalkane, a series of bis-annelated biimidazolium salts is obtained.The conformations of these species are discussed with regard to their electronic absorption spectra and their 300-MHz 1H NMR spectra.The barriers for conformational inversion are found to be lower than for the corresponding bis-annelated 2,2'-bipyridinium salts.The redox properties of these salts are measured in CH3CN and DMSO, and their reductions are found to become increasingly more difficult and less reversible as the system becomes less planar.These results are explained primarily based on the greater N,N'-distance in 2,2'-biimidazole as compared with 2,2'-bipyridine.