Novel Heterocyclic Electron Acceptor Materials

The objective of this study was to investigate the influence the introduction of a nitrogen containing heterocyclic spacer unit between the pyridinium termini of the viologen (1,1'-dialkyl(aryl)-[4,4'-bipyridine]-1,1'-diium) unit upon the electrochromic properties (reduction potential, reversibility, radical cation colour and background colour). The central heterocyclic spacer unit was selected from either a pyridine, quinoline, isoquinoline or imidazole ring or their respective N-quaternised salts.