Inorganic-organic hybrid photochromic materials.

Regioselective annulation of propargyl alcohols with ambident-enols: A Ca(II)-catalyzed trisubstituted benzochromene synthesis

A new synthetic route for biologically interesting benzochromenes was developed starting from naphthalenols and α,β-unsaturated aldehydes in the presence of ethylenediamine diacetate. This methodology was applied for the total synthesis of the biologically important natural products lapachenole, dihydrolapachenole, and mollugin with a benzochromene moiety.

A Novel Method for the Synthesis of Substituted Benzochromenes by Ethylenediamine Diacetate‐Catalyzed Cyclizations of Naphthalenols to α,β‐Unsaturated Aldehydes. Concise Synthesis of the Natural Products Lapachenole, Dihydrolapachenole, and Mollugin

Publisher Summary
This chapter discusses that significant advances in our understanding of the photochromic properties of naphthopyrans that have been made in the past decade Such is the structural diversity of naphthopyrans now available that it is possible to achieve almost any shade of any color. Furthermore, control of the fade rate with half-lives of less than a second to many hours is possible, thereby supplementing the fast and strong coloration and increasing the potential applications of these long-lived materials. Their facile synthesis from readily available precursors has allowed the commercial development of naphthopyrans to proceed at a good pace through the efforts of a small number of research groups linked to international manufacturers. The major end user is the ophthalmic industry. Brown or grey sun lenses can now be based on a single photochromic naphthopyran, whereas less than 20 years ago, multicomponent lenses were the norm. Naphthopyrans are used in security inks and as identity markers in a variety of products. Future uses in cosmetic applications and as devices are under development.

Chapter 3 – Photochromic naphthopyrans

Kinetics of photochromic reactions in condensed phases.

The synthesis, photochromic behaviour, photodegradation parameters and fluorescence spectra of a range of benzo- and dibenzochromenes substituted by a ferrocenyl group in the 2-position have been investigated. The ferrocenyl group leads to two absorption bands in the visible spectrum of the photomerocyanine species, in contrast to the single band observed with corresponding phenyl substituted derivatives. It also increases the thermal rate of bleaching of the photomerocyanine.

Synthesis and photochromic properties of ferrocenyl substituted benzo- and dibenzochromenes

Previous studies have shown that the substitution by a ferrocenyl group in the 2-position of naphthopyrans has a specific and an original effect on the photochromic behaviour. In this work, the synthesis and the photochromic properties of new naphthopyrans substituted in the 2-position by three different metallocenyl groups (ferrocenyl, ruthenocenyl and osmocenyl) are presented. Whereas the ferrocenyl-substituted derivatives under UV irradiation show two absorption bands, the ruthenocenyl and osmocenyl derivatives are characterized by only one absorption band under the same condition. The photochromic behaviour of these compounds is compared with that of their parent alkyl or phenyl 2-substituted [2H]-naphtho[1,2-b]pyrans. Copyright © 2002 John Wiley & Sons, Ltd.

Metallocenyl-[2H]naphtho[1,2-b]pyrans: metal effect on the photochromic behaviour

The study of the photochromic behaviour of a series of 2-ferrocenyl-2-methyl[2H]-chromenes has shown original spectrokinetic properties: the broadening of the absorption spectrum of the photomerocyanines with the appearance of a second band in the visible area and also important kinetic modifications in polar protic solvents giving to this series of chromenes a special interest From spectrokinetic results, a structure of photomerocyanines stabilised by polar and protic solvent such as alcohols could be proposed

Spectrokinetic study of a series of photochromic 2-ferrocenyl-2-methyl[2H]-chromenes

The synthesis and the photochromic properties of a new family of naphthopyrans substituted in the -3 position by a ferrocenyl group are presented. The photochromic behaviour of these compounds is compared with the parent -3,3-diphenyl-naphthopyrans ones. It shows quite original photochromic properties: extended wavelength range in the visible absorption spectrum, sensitivity of the spectrokinetic parameters to the annellation type. Introduction: The 2/7-benzopyrans (2//-chromenes) are known as an important class of photochromic materials (1). When exposed to UV irradiation they are converted into coloured merocyanine forms by cleavage of the C-O bond (Scheme 1). These photomerocyanines are highly conjugated forms and absorb in the visible range. The reaction is reversible and the back cyclisation generally takes place by a thermal process and sometimes also by a photochemical process in the visible region. Photochromic materials are characterised by three main parameters: the λTM* of the opened form, the colourability A«,, under continuous irradiation (or Ao by flash photolysis) and the thermal ring closure kinetic constant kA (2). Previous works have shown that the introduction of conjugated substituents in the -2 position of 2//-chromenes or in the -3 position of naphthopyrans (R and R) have interesting effects on the spectrokinetic parameters: decrease of the kA, increase of the A«, and important bathochromic shift of the λ ^ (3, 4, 5). uncoloured form δ_ coloured form Scheme 1: Photochromic equilibrium

New ferrocenyl-naphthopyrans with original photochromic behaviour

The spectral and kinetic characteristics for a number of ferrocenyl substituted naphthopyrans as compared with diphenyl substituted analogs are presented. The effect of the ferrocenyl substituent on photoinduced absorption and luminescent properties as well as the kinetic characteristics of photochromic transformations and photodegradation was studied.

Stéphane Anguille

Papers

Synthesis and photochromic properties of ferrocenyl substituted benzo- and dibenzochromenes

Metallocenyl-[2H]naphtho[1,2-b]pyrans: metal effect on the photochromic behaviour

Spectrokinetic study of a series of photochromic 2-ferrocenyl-2-methyl[2H]-chromenes

New ferrocenyl-naphthopyrans with original photochromic behaviour

Photochromic Properties of Ferrocene Substituted Chromenes