The synthesis and electrochemical study of new electrochromic viologen-based materials

Abstract

A range of diquaternary salts of 4,4′-bipyridine and 3,8-phenanthroline were prepared and subsequently screened using electrochemical and spectroscopic techniques. It was determined that the stability of the radical film deposited on cathodic reduction of aqueous solutions of these salts may be strongly influenced by symmetry, steric, and electronic factors. From this basis, it was possible to design a viologen, 1,1′-bis-(2-methylbenzyl)-2-methyl-4,4′-bipyridinium dibromide (9), having electrochromic properties for electronic display applications superior to those already in existence. A radical film of mixed composition was found to be less susceptible to ageing effects than films generated from the individual dicationic salts.