Indigo dye

Indigo
Names
	Preferred IUPAC name [2(2')E]-[2,2'-Biindolylidene]-3,3'(1H,1'H)-dione
	Other names 2,2'-Bis(2,3-dihydro-3-oxoindolyliden), Indigotin
Identifiers
CAS Number	64784-13-0 ;
3D model (JSmol)	Interactive image;
ChEMBL	ChEMBL599552 ;
ChemSpider	4477009 ;
ECHA InfoCard	100.006.898
PubChem CID	10215;
RTECS number	DU2988400;
UNII	1G5BK41P4F ;
CompTox Dashboard (EPA)	DTXSID3026279 ;
	InChI InChI=1S/C16H10N2O2/c19-15-9-5-1-3-7-11(9)17-13(15)14-16(20)10-6-2-4-8-12(10)18-14/h1-8,17-18H/b14-13+ Key: COHYTHOBJLSHDF-BUHFOSPRSA-N ; InChI=1/C16H10N2O2/c19-15-9-5-1-3-7-11(9)17-13(15)14-16(20)10-6-2-4-8-12(10)18-14/h1-8,17-18H/b14-13+ Key: COHYTHOBJLSHDF-BUHFOSPRBQ;
	SMILES c1ccc2c(c1)C(=O)/C(=C\3/C(=O)c4ccccc4N3)/N2;
Properties
Chemical formula	C16H10N2O2
Molar mass	262.27 g/mol
Appearance	dark blue crystalline powder
Density	1.199 g/cm3
Melting point	390 to 392 °C (734 to 738 °F; 663 to 665 K)
Boiling point	decomposes
Solubility in water	990 µg/L (at 25 °C)
Related compounds
Related compounds	Indoxyl; Tyrian purple; Indican
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Indigo dye is an organic compound with a distinctive blue color. Indigo is a natural dye obtained from the leaves of some plants of the Indigofera genus, in particular Indigofera tinctoria. Dye-bearing Indigofera plants were once common throughout the world. It is now produced via chemical routes. Blue colorants are rare. Since indigo is insoluble, it is also referred to as a pigment (C.I. Pigment Blue 66, C.I.).

Most indigo dye produced today is synthetic, constituting around 80,000 tonnes each year, as of 2023. It is most commonly associated with the production of denim cloth and blue jeans, where its properties allow for effects such as stone washing and acid washing to be applied quickly.