6,6'-Dibromoindigo

6,6'-Dibromoindigo
Names
	Other names 6BrIG; Tyrian purple
Identifiers
CAS Number	1277170-99-6;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:80914;
ChemSpider	4590500;
KEGG	C17084;
PubChem CID	177057;
UNII	2O3DDL8TAF;
CompTox Dashboard (EPA)	DTXSID801314818 ;
	InChI InChI=1S/C16H8Br2N2O2/c17-7-1-3-9-11(5-7)19-13(15(9)21)14-16(22)10-4-2-8(18)6-12(10)20-14/h1-6,19,21H; Key: UOZOCOQLYQNHII-UHFFFAOYSA-N;
	SMILES C1=CC2=C(C=C1Br)NC(=C2O)C3=NC4=C(C3=O)C=CC(=C4)Br;
Properties
Chemical formula	C16H8Br2N2O2
Molar mass	420.060 g·mol−1
Appearance	purple solid
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

6,6'-Dibromoindigo is an organic compound with the formula (BrC₆H₃C(O)CNH)₂. A deep purple solid, the compound is also known as Tyrian purple, a dye of historic significance. Presently, it is only a curiosity, although the related derivative indigo is of industrial significance. It is produced by molluscs of the Muricidae species.^[1]

The pure compound has semiconductor properties in the thin film phase, which is potentially useful for wearable electronics, and has better performance than the parent indigo in this context.^[2]^[3]

Biosynthesis

Biosynthesis of the molecule is intermediated by tyrindoxyl sulphate.^[4] The molecule consists of a pair of monobrominated indolin-3-one rings linked by a carbon-carbon double bond.

Dibromoindigo can also be produced enzymatically in vitro from the amino acid tryptophan. The sequence begins with bromination of the benzo ring followed by conversion to 6-bromoindole. Flavin-containing monooxygenase then couples two of these indole units to give the dye.

Chemical synthesis

The main chemical constituent of the Tyrian dye was discovered by Paul Friedländer in 1909 to be 6,6′-dibromoindigo, derivative of indigo dye, which had been synthesized in 1903.^[5]^[6] Although the first chemical synthesis was reported in 1914, unlike indigo, it has never been synthesized at commercial level.^[7]^[8] An efficient protocol for laboratory synthesis of dibromoindigo was developed in 2010.^[9]

References

^ McGovern, Patrick E.; Michel, R. H. (1990). "Royal Purple dye: The chemical reconstruction of the ancient Mediterranean industry". Accounts of Chemical Research. 23 (5): 152–158. doi:10.1021/ar00173a006.
^ Pandolfi, Lorenzo; Rivalta, Arianna; Salzillo, Tommaso; Giunchi, Andrea; D’Agostino, Simone; Della Valle, Raffaele G.; Brillante, Aldo; Venuti, Elisabetta (13 August 2020). "In Search of Surface-Induced Crystal Structures: The Case of Tyrian Purple". The Journal of Physical Chemistry C. 124 (32): 17702–17710. doi:10.1021/acs.jpcc.0c05186. hdl:11585/786088.
^ "Tyrian purple: The lost ancient pigment that was more valuable than gold". www.bbc.com.
^ Valles-Regino, Roselyn; Mouatt, Peter; Rudd, David; Yee, Lachlan; Benkendorff, Kirsten (2016). "Extraction and Quantification of Bioactive Tyrian Purple Precursors: A Comparative and Validation Study from the Hypobranchial Gland of a Muricid Dicathais orbita". Molecules. 21 (12): 1672. doi:10.3390/molecules21121672. PMC 6273837. PMID 27929402.
^ Friedlaender, P. (1909). "Zur Kenntnis des Farbstoffes des antiken Purpurs aus Murex brandaris" [Towards understanding the ancient purple dye from Murex brandaris]. Monatshefte für Chemie. 30 (3): 247–253. doi:10.1007/BF01519682. S2CID 97865025.
^ Sachs, Franz; Kempf, Richard (1903). "Über p-Halogen-o-nitrobenzaldehyde". Berichte der Deutschen Chemischen Gesellschaft. 36 (3): 3299–3303. doi:10.1002/cber.190303603113.
^ "Indigo". Encyclopædia Britannica. Vol. V (15th ed.). Chicago, IL: Encyclopædia Britannica, Inc. 1981. p. 338. ISBN 0-85229-378-X.
^ Cooksey, C.J. (2001). "Tyrian purple: 6,6'-dibromoindigo and related compounds" (PDF). Molecules. 6 (9): 736–769. doi:10.3390/60900736. S2CID 5592747.
^ Wolk JL, Frimer AA (August 2010). "A simple, safe and efficient synthesis of Tyrian purple (6,6'-dibromoindigo)". Molecules. 15 (8): 5561–5580. doi:10.3390/molecules15085561. PMC 6257764. PMID 20714313.

[1] McGovern, Patrick E.; Michel, R. H. (1990). "Royal Purple dye: The chemical reconstruction of the ancient Mediterranean industry". Accounts of Chemical Research. 23 (5): 152–158. doi:10.1021/ar00173a006.

[2] Pandolfi, Lorenzo; Rivalta, Arianna; Salzillo, Tommaso; Giunchi, Andrea; D’Agostino, Simone; Della Valle, Raffaele G.; Brillante, Aldo; Venuti, Elisabetta (13 August 2020). "In Search of Surface-Induced Crystal Structures: The Case of Tyrian Purple". The Journal of Physical Chemistry C. 124 (32): 17702–17710. doi:10.1021/acs.jpcc.0c05186. hdl:11585/786088.

[3] "Tyrian purple: The lost ancient pigment that was more valuable than gold". www.bbc.com.

[4] Valles-Regino, Roselyn; Mouatt, Peter; Rudd, David; Yee, Lachlan; Benkendorff, Kirsten (2016). "Extraction and Quantification of Bioactive Tyrian Purple Precursors: A Comparative and Validation Study from the Hypobranchial Gland of a Muricid Dicathais orbita". Molecules. 21 (12): 1672. doi:10.3390/molecules21121672. PMC 6273837. PMID 27929402.

[5] Friedlaender, P. (1909). "Zur Kenntnis des Farbstoffes des antiken Purpurs aus Murex brandaris" [Towards understanding the ancient purple dye from Murex brandaris]. Monatshefte für Chemie. 30 (3): 247–253. doi:10.1007/BF01519682. S2CID 97865025.

[6] Sachs, Franz; Kempf, Richard (1903). "Über p-Halogen-o-nitrobenzaldehyde". Berichte der Deutschen Chemischen Gesellschaft. 36 (3): 3299–3303. doi:10.1002/cber.190303603113.

[7] "Indigo". Encyclopædia Britannica. Vol. V (15th ed.). Chicago, IL: Encyclopædia Britannica, Inc. 1981. p. 338. ISBN 0-85229-378-X.

[8] Cooksey, C.J. (2001). "Tyrian purple: 6,6'-dibromoindigo and related compounds" (PDF). Molecules. 6 (9): 736–769. doi:10.3390/60900736. S2CID 5592747.

[9] Wolk JL, Frimer AA (August 2010). "A simple, safe and efficient synthesis of Tyrian purple (6,6'-dibromoindigo)". Molecules. 15 (8): 5561–5580. doi:10.3390/molecules15085561. PMC 6257764. PMID 20714313.

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