Photochromic organic–inorganic hybrid materials have attracted considerable attention owing to their potential application in photoactive devices, such as optical memories, windows, photochromic decorations, optical switches, filters or non-linear optics materials. The growing interest in this field has largely expanded the use of photochromic materials for the purpose of improving existing materials and exploring new photochromic hybrid systems. This tutorial review summarizes the design and preparation of photochromic hybrid materials, and particularly those based on the incorporation of organic molecules in organic–inorganic matrices by the sol–gel method. This is the most commonly used method for the preparation of these materials as it allows vitreous hybrid materials to be obtained at low temperatures, and controls the interaction between the organic molecule and its embedding matrix, and hence allows tailoring of the performance of the resulting devices.

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Photochromic organic-inorganic hybrid materials.

A new class of thermally irreversible and fatigue resistant photochromic molecules named diarylethenes has been developed Theoretical consideration based on the state correlation diagrams of electrocyclic reactions revealed that the thermal irreversibility is attained by introducing aryl groups that have low aromatic stabilization energy According to the molecular design principle thermally irreversible photochromic diarylethenes having heterocyclic five-membered rings, such as furan, thiophene (or benzothiophene), or thiazole rings, have been newly synthesized Among them, diarylethenes having benzothiophene aryl groups showed an excellent fatigue resistant property They underwent photochromic cycles more than 10 × 104 times The absorption maxima of the closed-ring forms varied from 425 to 828 nm depending on the aryl groups, substituents of the aryl groups, and the substitution position of the aryl groups to the ethane moiety The response times of both cyclization and ring-opening reactions were l

Synthesis and Properties of Photochromic Diarylethenes with Heterocyclic Aryl Groups.

Molecular systems encompassing more than one photochromic entity can be used to build highly functional materials, thanks to their potential multi-addressability and/or multi-response properties. Over the last decade, the synthesis and spectroscopic and kinetic characterisation as well as the modeling of a wide range of multiphotochromes have been achieved in a field that is emerging as a distinct branch of photochemistry. In this review, we provide an overview of the available multiphotochromic compounds which use a variety of photoactive building blocks, e.g., diarylethene, azobenzene, spiropyran, naphthopyran or fulgimide derivatives. Their efficiency in terms of multi-responsiveness is discussed and several strategies to circumvent the most common limitation (i.e., the loss of photochromism of one part) are described.

Multiphotochromic molecular systems

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Photoluminescent and Chromic Nanomaterials for Anticounterfeiting Technologies: Recent Advances and Future Challenges.

Described are novel photochromic indeno-fused naphthopyran compounds, examples of which are naphthopyran compounds having a substituted or unsubstituted indeno group, the 2,1 positions of which are fused to the f side of the naphtho portion of the naphthopyran, and certain substituents at the 3-position of the pyran ring. Certain substituents may also be present at the number 5, 6, 7, 8, 9, 10, 11, 12, or 13 carbon atoms of the compounds. These compounds may be represented by the following graphic formula: ##STR1## Also described are polymeric organic host materials that contain or that are coated with such compounds. Optically clear articles such as ophthalmic lenses or other plastic transparencies that incorporate the novel naphthopyran compounds or combinations thereof with complementary photochromic compounds, e.g., certain other naphthopyrans, benzopyrans, and spiro(indoline)type compounds, are also described.

Photochromic indeno-fused naphthopyrans

Described are novel reversible photochromic naphthopyran compounds, examples of which are 3H-naphtho[2,1-b]pyrans having an acyl or aroyl oxy-bearing substituent at the number 6 carbon atom and certain substituents at the 3-position of the pyran ring. Certain substituents may also be present at the number 5, 7, 8, 9 or 10 carbon atom of the naphthopyran. These compounds may be represented by graphic formula (I). Also described are polymeric organic host materials that contain or that are coated with such compounds. Optically clear articles such as ophthalmic lenses or other plastic transparencies that incorporate the novel naphthopyran compounds or combinations thereof with complementary photochromic compounds, e.g., certain other naphthopyrans, benzopyrans, and spiro(indoline) type compounds, are also described.

Photochromic substituted naphthopyran compounds

Described are novel photochromic polymerizable polyalkoxylated naphthopyran compounds, examples of which are certain 2H-naphtho[1,2-b]pyrans, 3H-naphtho[2,1-b]pyrans and indeno[2,1-f]naphtho[1,2-b]pyrans each having at least one polyalkoxylated substituent of from 1 to 50 alkoxy units per substituent which is end-capped with a polymerizable group. Specific substituents are also present on the naphtho, indeno and pyrano portions of the compounds. These compounds may be represented by graphic formulae (I), (II) or (III). Also described are various substrates, e.g., paper, glass, polymeric organic materials, etc., that contain or that are coated with such compounds. Optically clear articles such as contact lenses or other plastic transparencies that incorporate the novel naphthopyran compounds or combinations thereof with complementary photochromic compounds, e.g., certain other naphthopyrans, indenonaphthopyrans, benzopyrans, oxazine-type compounds, etc., are also described.

Polymerizable polyalkoxylated naphthopyrans

Described are novel photochromic indeno-fused naphthopyran compounds, examples of which include naphthopyran compounds having a substituted or unsubstituted indeno group, the 2,1 positions of which are fused to the naphtho portion of the naphthopyran as shown below. Also present on the naphthopyran are moderate to strong electron donor substituents at the number 6- and 7-positions and optionally at the 8-position of the pyran ring or a cyclic group fused to the h side of the naphtho portion and weak to moderate electron donor substiuents at the 3-position of the pyran ring. Certain substituents may also be present at the number 5, 8, 9, 10, 11, 12, or 13 carbon atoms of the compounds. These compounds have a rating of at least 80 in the Relative ΔOD at Saturation Test and may be represented by the following graphic formula: Also described are polymeric organic host materials that contain or that are coated with such compounds. Optically clear articles such as ophthalmic lenses or other plastic transparencies that incorporate the novel naphthopyran compounds or combinations thereof with complementary photochromic compounds, e.g., certain other naphthopyrans, benzopyrans, and spiro(indoline)type compounds, are also described.

Indeno-fused photochromic naphthopyrans

A series of 3,3-diaryl-3H-naphtho[2,1-b]pyrans were prepared and their photochromic properties measured in plastic matrix. The influence of a variety of substituents on color, intensity, and fade were studied.

Photochromism of Diarylnaphthopyrans

Described are novel reversible photochromic naphthopyran compounds which have two phenyl moieties adjacent to each oxygen of each pyran ring. The substituents on each pair of phenyl moieties mirror one another when the phenyl groups are substituted. The naphthodipyrans are prepared from β,β-dihydroxynaphthalene compounds.

Barry Van Gemert

Papers

Photochromic substituted naphthopyran compounds

Polymerizable polyalkoxylated naphthopyrans

Indeno-fused photochromic naphthopyrans

Photochromism of Diarylnaphthopyrans

Photochromic tetraphenyl naphthodipyrans