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.^[1]

Indanthrone blue

Skeletal formula
Ball-and-stick model
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
CAS Number	81-77-6 Y
3D model (JSmol)	Interactive image
Beilstein Reference	367131
ChemSpider	6435 Y
ECHA InfoCard	100.001.251
E number	E130 (colours)
PubChem CID	6690
UNII	R68OT0N83K Y
CompTox Dashboard (EPA)	DTXSID2026280
InChI 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 Y Key: UHOKSCJSTAHBSO-UHFFFAOYSA-N Y 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
SMILES O=C6c5c4Nc3c(c2C(=O)c1ccccc1C(=O)c2cc3)Nc4ccc5C(=O)c7ccccc67
Properties
Chemical formula	C28H14N2O4
Molar mass	442.430 g·mol−1
Appearance	dark blue solid
Density	1.6 g/ml
Melting point	470-500 °C (decomposes)
Solubility in water	Insoluble
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Preparation

The compound is made from 2-aminoanthraquinone treated with potassium hydroxide.

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]

Applications

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.^[3][4] It has excellent light fastness, but may bleed in some organic solvents.

Organic Semiconductor

As an organic semiconductor, indanthrone has capabilities for utilization as a photocatalyst for oxygen generation from water utilizing solar energy.^[5][6] 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.^[7]

Colorant

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.^[8] 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.

Trademark

Indanthrone blue was the first example of the brand "Indanthren" (an acronym for Indigo from anthracene) introduced by BASF in 1901.^[9][10][11] 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.^[12][13]