Merck, 84120-25G, Safranin O

Safranin O, also known as Basic Red 2, is a basic, cationic, and metachromatic azine dye used as a biological stain. The characteristic azine chromophore contains the phenazine, a planar, tricyclic dibenzopyrazine, which consists of two non-planar benzene rings linked by two nitrogen atoms. A delocalized positive charge, an alternation of aromatic and quinonoid structures, and diazotizable amine groups constitute the chromophoric system. c-Methylation makes this dye of moderate overall size. The trimethyl cationic form of safranine is lipophilic, whereas the dimethyl forms are weakly hydrophilic. The dye is commercially available as a chloride.