Indanthrone blue

Indanthrone blue, also called indanthrene, is an organic compound with the formula Template:Chem2. It is a dark blue solid that is a common dye as well as a precursor to other dyes.<ref>Template:Cite book</ref>

Preparation

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

synthesis of indanthrone

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.<ref>Template:Citation</ref>

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.<ref>Summary of Color Additives for Use in the United States in Foods, Drugs, Cosmetics, and Medical Devices, Food and Drug Administration</ref><ref>Current EU approved additives and their E Numbers, Food Standards Agency</ref> 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.<ref>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).</ref><ref>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.</ref> 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.<ref>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.</ref>

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.<ref name=herbst>W. Herbst, K. Hunger: Industrial Organic Pigments. Preparation, properties, application. 2nd ed., Wiley-VCH, Weinheim 1995, ISBN 3-527-28744-2.</ref> 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.<ref name=roempp>Template:RömppOnline</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite book</ref> 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>