Besides the Me-Vi molecule, we study 4,4'-dimethyldiquat 23 (DMDQ), desalted Basic Red 5 (dBR5), 2-hydroxy-1,4-naphthaquinone (2HNQ), and 1,1'-di(2-ethanol)-4,4'-bipyridinium (OH-Vi) molecules. The structures of these molecules are represented in Fig. . All of these species have been tested as strong negolyte candidates in ORFB cells. Although Me-Vi, OH-Vi and DMDQ are theoretically capable of a second ET, in practice they cannot dissolve in water after the reduction reactions. Their ability to work in nearly pH-neutral solutions can be one of their main advantages. In contrast, 2-HNQ and dBR5 both are protonated during the reduction reactions. Generally, reactions that include protons are slower and result in a lower electrochemical rate constant.