Polymer effect in electrochromic behavior of oligomeric viologens

A series of oligomeric viologens were synthesized in order to investigate the polymer effect in electrochromic behavior of viologen compounds. These materials have a lower first‐step reduction potential and a higher second‐step reduction potential compared with monomeric viologens. As a result, they have wider potential separation, where stable viologene radical salts are produced. Spectroscopic analysis suggests that stable monomeric viologen radical salts do not exist in water, but there is some intramolecular interaction between viologen radicals of the oligomers. This intramolecular interaction is responsible for the reduction behavior and the stability of radical films of oligomeric viologens.