Photochromism in Anils - A Review

M.S.M. Rawat1, *, Sudagar Mal2, #, Pramod Singh1
1 Department of Chemistry, H. N. B. Garhwal University, (A Central University), Srinagar Garhwal, Uttarakhand, 246174, India;
2 Chemistry Division, ONGC, Baroda, India

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© Rawat et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Department of Chemistry, H. N. B. Garhwal University, (A Central University) Srinagar (Garhwal), Uttarakhand, India - 246 174; E-mail:
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This review describes in brief the historical perspective of photochromism and photochromic behaviour of ‘Anils’. This phenomenon among ‘Anils’ is exhibited due to the tautomerism between enol and keto form via six membered hydrogen transfer between the phenolic hydrogen and imine nitrogen and show the phenomenon of solid-state photochromism and thermochromism and photochromism in rigid glassy solutions as well. Photochromic property in ‘Anils’ is a characteristic of the molecule, but their chromo behaviour is not only influenced by the crystal structure of anils but also by the substituents in the salicylidene-aniline molecules by affecting the acidity of phenolic oxygen as well as the basicity of imine nitrogen that affects the enolic-character of anils. The growing interest in photochromic anils is due to the potential applications, more specifically due to the existence of anils in enolic- and keto- forms.

Keywords: Anils, photochromism, salicylidine anilines, Schiff’s bases, thermochromism.