The name indicates that the compounds are a fusion of acridone and quinoline, although they are not made that way. Classically the parent is prepared from the 2,5-dianilide of terephthalic acid (C6H2(NHPh)2(CO2H)2). Condensation of succinosuccinate esters with aniline followed by cyclization affords dihydroquinacridone, which are readily dehydrogenated. The latter is oxidized to quinacridone.[1] Derivatives of quinacridone can be readily obtained by employing substituted anilines. Linear cis-Quinacridones can be prepared from isophthalic acid.[3][4]
Derivatives
Isomers of quinacridone
Linear trans-Isomer
Linear cis-Isomer
Angular cis-Isomer
Angular trans-Isomer
Quinacridone-based pigments are used to make high performance paints. Quinacridones were first sold as pigments by Du Pont in 1958.[5] Quinacridones are considered "high performance" pigments because they have exceptional color and weather fastness. Major uses for quinacridones include automobile and industrial coatings. Nanocrystalline dispersions of quinacridone pigments functionalized with solubilizingsurfactants are the most common magenta printing ink.
Typically deep red to violet in color, the hue of quinacridone is affected not only by the R-groups on the molecule but by the crystal form of the solid. For example, the γ crystal modification of unsubstituted quinacridone provides a strong red shade that has excellent color fastness and resistance to solvation. Another important modification is the β phase which provides a maroon shade that is also more weather resistant and light-fast. Both crystal modifications are more thermodynamically stable than the α crystal phase. The γ crystal modification is characterized by a criss-cross lattice where each quinacridone molecule hydrogen-bonds to four neighbors via single H-bonds. The β phase, meanwhile, consists of linear chains of molecules with double H-bonds between each quinacridone molecule and two neighbors.[6]
Basic modifications to the chemical structure of quinacridones include the addition of CH3 and Cl substituents. Some magenta shades of quinacridone are labeled under the proprietary name "Thio Violet"[7] and "Acra Violet".[8]
^Labana, S. S.; Labana, L. L. (1967). "Quinacridones". Chemical Reviews. 67: 1–18. doi:10.1021/cr60245a001.
^Lincke, Gerhard (2002). "On quinacridones and their supramolecular mesomerism within the crystal lattice". Dyes and Pigments. 52 (3): 169–181. doi:10.1016/S0143-7208(01)00085-7.
^Lomax, Suzanne Quillen (13 December 2013). "Phthalocyanine and quinacridone pigments: their history, properties and use". Studies in Conservation. 50 (sup1): 19–29. doi:10.1179/sic.2005.50.Supplement-1.19. S2CID97211023.
