Article · Wikipedia archive · Last revised Jun 9, 2026

Indanthrone blue

Indanthrone blue, also called indanthrene, is an organic compound with the formula (C14H6O2NH)2. It is a dark blue solid that is a common dye as well as a precursor to other dyes.

Last revised
Jun 9, 2026
Read time
≈ 4 min
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Citations
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Source
Wikipedia ↗
Indanthrone blue
Skeletal formula
Skeletal formula source ↗
Ball-and-stick model
Ball-and-stick model source ↗
Names
Preferred IUPAC name
6,15-Dihydrodinaphtho[2,3-a:2′,3′-h]phenazine-5,9,14,18-tetrone
Other names
C.I. vat blue 4, carbon paper blue, blue O, carbanthrene blue 2R, fenan blue RSN, graphtol blue RL, medium blue, monolite fast blue 3R, indanthrene, indanthrone, pigment blue 60, C.I. 69800
Identifiers
3D model (JSmol)
367131
ChemSpider
ECHA InfoCard 100.001.251
E number E130 (colours)
UNII
  • InChI=1S/C28H14N2O4/c31-25-13-5-1-3-7-15(13)27(33)21-17(25)9-11-19-23(21)29-20-12-10-18-22(24(20)30-19)28(34)16-8-4-2-6-14(16)26(18)32/h1-12,29-30H checkY
    Key: UHOKSCJSTAHBSO-UHFFFAOYSA-N checkY
  • InChI=1/C28H14N2O4/c31-25-13-5-1-3-7-15(13)27(33)21-17(25)9-11-19-23(21)29-20-12-10-18-22(24(20)30-19)28(34)16-8-4-2-6-14(16)26(18)32/h1-12,29-30H
    Key: UHOKSCJSTAHBSO-UHFFFAOYAY
  • O=C6c5c4Nc3c(c2C(=O)c1ccccc1C(=O)c2cc3)Nc4ccc5C(=O)c7ccccc67
Properties
C28H14N2O4
Molar mass 442.430 g·mol−1
Appearance dark blue solid
Density 1.6 g/ml
Melting point 470-500 °C (decomposes)
Insoluble
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Indanthrone blue, also called indanthrene, is an organic compound with the formula (C14H6O2NH)2. It is a dark blue solid that is a common dye as well as a precursor to other dyes.1

Preparation and structure

The compound is made by oxidation of 2-aminoanthraquinone in the presence of potassium hydroxide.

synthesis of indanthrone
synthesis of indanthrone source ↗
Procedure for producing indanthrone from 2-aminoanthraquinone.

By dimerization of 2-aminoanthraquinone]] (1) under strongly alkaline conditions at 220-235 °C, the intermediate 3 is obtained in two steps, which cyclizes intramolecularly and is oxidized to indanthrone 5.2

Owing to intermolecular hydrogen bonding, indanthrone is insoluble. It can be modified by installing tert-butyloxycarbonyl groups in place of the N-H groups to give an organic-soluble "latent pigment." Processing of such derivatives has affording crystals of the parent pigment.3

Applications

Indanthrone is utilized as a blue pigment (C.I. Pigment Blue 60), primarily in the process of vat dyeing, often referred to as C.I. Vat Blue 4.4 Indanthrone is a vat dye, synthesized to provide highest color fastness for the dyeing and printing of predominantly cellulose-based textile fibers. Fabrics dyed with indanthrene fulfill the highest standards and exhibit exceptional wash fastness, boil fastness, light fastness, weather fastness and chlorine fastness.

It is a pigment that can be used in the following media: acrylic, alkyd, casein, encaustic, fresco, gouache, linseed oil, tempera, pastel, and watercolor painting. It is used to dye unmordanted cotton and as a pigment in quality paints and enamels. As a food dye, it has number 130, but it is not approved for use in either the United States or the European Union.56 It has excellent light fastness, but may bleed in some organic solvents.

Indanthrone blue was the first example of the brand "Indanthren" (an acronym for Indigo from anthracene) introduced by BASF in 1901.789 One result is that even now, in Japan vat dyes are commonly described as threne dyes (スレン染料), derived from the Japanese transliteration of the brand.1011

Signifigance of Indigo Pure BASF in Indanthrene Blue

The color and vat dye that came before Indanthrene Blue was Indigo Pure BASF. This synthesis consisted of Phenylglycocoll acid mixed and fused with Caustic soda which transforms into an alkaline solution. When this Alkaline solution makes contact with oxygen, the color Indigo precipitates/appears. This process would be replicated in various ways to create Indanthrene blue and its derivatives. Indigo Pure BASF contributed to the research as a cornerstone of its progress as the chemists at BASF took 17 years to research and synthesize this vat dye.1213

Other studies

As an organic semiconductor, indanthrone has been considered as a photocatalyst for oxygen generation from water utilizing solar energy.1415 Indanthrone's characteristic as a nonlinear optics light absorber, allows for its use as an optical limiter, which can be employed, for instance, in laser protective filters.16

Indrathren Blue CLB (PubChem CID 5483458, registry number 6492-78-0) is a related blue dye.

References

References

  1. Bien, Hans-Samuel; Stawitz, Josef; Wunderlich, Klaus (2000). "Anthraquinone Dyes and Intermediates". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a02_355. ISBN 3527306730.
  2. Heinrich Zollinger (2003), Color Chemistry: Syntheses, Properties, and Applications of Organic Dyes and Pigments (3. ed.), Weinheim: WILEY-VCH Verlag, p. 289, ISBN 3-906390-23-3
  3. Liu, Tang-Hao; Cheng, Wen-Tung; Huang, Kou-Tung (2014). "Crystallization and morphology of indanthrone converted from latent pigment in the solution with photo acid generator". Dyes and Pigments. 105: 137–144. doi:10.1016/j.dyepig.2014.01.021.
  4. W. Herbst, K. Hunger: Industrial Organic Pigments. Preparation, properties, application. 2nd ed., Wiley-VCH, Weinheim 1995, ISBN 3-527-28744-2.
  5. Summary of Color Additives for Use in the United States in Foods, Drugs, Cosmetics, and Medical Devices, Food and Drug Administration
  6. Current EU approved additives and their E Numbers, Food Standards Agency
  7. Entry on Indanthron-Pigmente. at: Römpp Online. Georg Thieme Verlag, retrieved 16. Januar 2013.
  8. "Marken - Registerauskunft - Indanthren". DPMAregister (in German). Retrieved 29 August 2020. Anmeldetag: 05.08.1901 / Inhaber: BASF AG
  9. Zollinger, Heinrich (2003). Color Chemistry: Syntheses, Properties, and Applications of Organic Dyes and Pigments. John Wiley & Sons. p. 255. ISBN 978-3-906390-23-9. Retrieved 29 August 2020. The German word Indanthren is an acronym for Indigo aus Anthrazen
  10. "Colourful World III". www.eonet.ne.jp. Retrieved 29 August 2020. バット染料の主たる製造元は、ドイツの化学会社でありその時の商標が、 "インダンスレン" であったことからスレン染料と呼ぶ場合も多くあります
  11. "アルテモンド 豆知識 / スレン染料". www.artemondo.co.jp. スレン染料（threne dye）とは、バット染料（vat dye）の俗称
  12. Gesellschaft Deutscher Chemiker. Chemische Berichte. Weinheim/Bergsr. [etc.]: VCH Verlagsgesellschaft mbH. [etc.],
  13. "1865 – 1901 / The Age of Dyes". BASF. 04/15/2026. Retrieved 04/15/2026.
  14. C. A. Linkous, D. K. Slattery: Solar photocatalytic hydrogen production from water using a dual bed photosystem. In Proceedings of the 2000 Hydrogen Program Annual Review, Volume I. (PDF).
  15. D. K. Slattery et al: Semiempirical MO and Voltammetric estimation of ionization potentials of organic pigments. Comparison to gas phase ultraviolet photoelectron spectroscopy. In: Dyes and Pigments 49, 2001, pp. 21-27.
  16. Y.-P. Sun, J. E. Riggs: Organic and inorganic optical limiting materials. From fullerenes to nanoparticles. In International Reviews in Physical Chemistry. 18, no. 1, 1999, pp. 43-90.