Pigment Red 38;Diethyl 4,4'-[(3,3'-dichlOrO[1,1'-biphenyl]-4,4'-diyl)bis(azO)]bis[4,5-dihydrO-5-OxO-1-phenyl-1H-pyrazOle-3-carbOxyla te]

Pigment Red 38 is a red dye that is used in the production of magnetic particles, cross-linking agents, and fluorescent dyes. Pigment Red 38 has a hydroxyl group at the 4 position and a methyl ethyl group at the 2 position. It can be synthesized from diethyl 4,4'-(3,3'-dichlorobiphenyl)-4,4'-diylbisazolate. Pigment Red 38 is thermoreversible because it can be converted to its anhydrous form when heated or dissolved in water and then reconverted back to its original form when cooled or dried. The pigment was named for its ability to produce light emission when exposed to ultraviolet radiation. Pigment Red 38 has a diameter of 6 nm and reacts with coordination complexes to form particle clusters with diameters ranging from 10-200 nm.