A Perspective on Indigo: An Iconic Colorant

This perspective sets out to raise awareness about the chemical and photophysical properties of indigo, a highly distinguished colorant with an extraordinary history. Indigo, like many other dyes, was first extracted from plants at an inordinately low yield and at great ecological expense. Such was...

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Main Author: Anthony Harriman
Format: Article
Language:English
Published: MDPI AG 2025-03-01
Series:Colorants
Subjects:
Online Access:https://www.mdpi.com/2079-6447/4/2/12
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author Anthony Harriman
author_facet Anthony Harriman
author_sort Anthony Harriman
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description This perspective sets out to raise awareness about the chemical and photophysical properties of indigo, a highly distinguished colorant with an extraordinary history. Indigo, like many other dyes, was first extracted from plants at an inordinately low yield and at great ecological expense. Such was its popularity that indigo was among the first natural colorants to be synthesized in a laboratory before refinement and cost reduction resulted in its economical industrial-scale production. The color of indigo is highly characteristic but difficult to describe, since it falls at the blue/violet interface. It is a small, planar molecule with an exceptionally high degree of π-electron conjugation that pushes the absorption maximum to above 600 nm. Its structure helps explain the high level of photostability enjoyed by indigo, while recent spectroscopic studies have added to our understanding of the longevity of this emblematic colorant. The reversible formation of <i>leuco</i>-indigo increases the ways in which indigo can be used to add color to objects while helping to circumvent the effects of attack by free radicals. It is stressed that the journal <i>Colorants</i> would welcome submissions that describe the chemistry and/or spectroscopy of other representative colorants.
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spelling doaj-art-f05946e417924e8296fa6f5f351e04c62025-08-20T03:26:56ZengMDPI AGColorants2079-64472025-03-01421210.3390/colorants4020012A Perspective on Indigo: An Iconic ColorantAnthony Harriman0Molecular Photonics Laboratory, School of Natural & Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UKThis perspective sets out to raise awareness about the chemical and photophysical properties of indigo, a highly distinguished colorant with an extraordinary history. Indigo, like many other dyes, was first extracted from plants at an inordinately low yield and at great ecological expense. Such was its popularity that indigo was among the first natural colorants to be synthesized in a laboratory before refinement and cost reduction resulted in its economical industrial-scale production. The color of indigo is highly characteristic but difficult to describe, since it falls at the blue/violet interface. It is a small, planar molecule with an exceptionally high degree of π-electron conjugation that pushes the absorption maximum to above 600 nm. Its structure helps explain the high level of photostability enjoyed by indigo, while recent spectroscopic studies have added to our understanding of the longevity of this emblematic colorant. The reversible formation of <i>leuco</i>-indigo increases the ways in which indigo can be used to add color to objects while helping to circumvent the effects of attack by free radicals. It is stressed that the journal <i>Colorants</i> would welcome submissions that describe the chemistry and/or spectroscopy of other representative colorants.https://www.mdpi.com/2079-6447/4/2/12photochemistryspectroscopystability
spellingShingle Anthony Harriman
A Perspective on Indigo: An Iconic Colorant
Colorants
photochemistry
spectroscopy
stability
title A Perspective on Indigo: An Iconic Colorant
title_full A Perspective on Indigo: An Iconic Colorant
title_fullStr A Perspective on Indigo: An Iconic Colorant
title_full_unstemmed A Perspective on Indigo: An Iconic Colorant
title_short A Perspective on Indigo: An Iconic Colorant
title_sort perspective on indigo an iconic colorant
topic photochemistry
spectroscopy
stability
url https://www.mdpi.com/2079-6447/4/2/12
work_keys_str_mv AT anthonyharriman aperspectiveonindigoaniconiccolorant
AT anthonyharriman perspectiveonindigoaniconiccolorant