Introducing photochromic compounds into supramolecular self-assembling systems endows the supramolecular nanostructures or materials with intriguing responsive behavior to light, which can be conveniently orthogonal to other stimuli. Carlson, The reaction of Grignard reagents with 4-hydroxy- and 4-ethoxycoumarin, J. In other words, there is no all-cis hexatriene unit in the Z form, which is an essential component for the photocyclization of fulgides. This effect can be clearly seen in methoxyphenyl fulgides, which have been extensively studied, as shown in Table 4. In the reaction between an arylamine and an a-hydroxyketone, a crucial step is the rearrangement of an imino-tert-alkanol to an anilinoketone. This is the proton-transfer reaction that gives the orange-colored anion of the nitrosalicylaldehyde and the colorless indoleninium cation.
However, the thermal decoloration reaction rate and the photoconversion efficiency of the photochromic molecules largely depend on their surrounding medium. Scheme 3 In an unusual variation of this first method, 2-methyleneindolines condense with pyrylium salts to give photochromic spiroindolines with a carbocyclic rather than a pyran ring. The structural calculations indicate that the colored form is essentially quinoidal, rather that zwitterionic. Arylation, however, for example, with 2,4-dinitrofluorobenzene or 4-nitrohalobenzenes, has not been successful. It should be noted that Volume 1 does not address thermochromism. It also effectively holds the phenyl group at the 6-position in plane with the naphthropyran, thereby extending the chromophore.
This page intentionally left blank. The overall yields, melting points, and spectroscopic properties of some aryl fulgides are listed in Table 4. Further studies on the photoreaction kinetics of thienyl fulgide derivatives 49a—49c have been carried out by the same research group, 59 as shown in Scheme 14. Fulgide Family Compounds: Synthesis, Photochromism and Applications 187 Scheme 28. Phosphorus trichloride gave the dichlorophosphinoindoline in 96% yield, whose chlorine atoms could be replaced by ethyl, phenyl, ethoxy, and dimethylamino groups in good yields. Yet another variation on the same theme links the two aryl groups together 32—34 to form spirofluorenylidene 18 spirosuberenylidene 19 and the like Figure 3. Photochromic Systems Based on Pentadienyl Anions with Two Heteroatoms.
The usual incompletely colored film is obtained if the heated dye source or the receiving substrate but not the vapor path is irradiated. A mixture of 45 g of paraformaldehyde and 750 ml of reagent-grade concd. Phenyl Fulgides Fulgides are aromatic substituted bismethylene succinic anhydride derivatives, the photochromism of which was first discovered by Stobbe. Two mutually perpendicular polarized lights will act independently, thus permitting a total of ten different recordings in the same volume. The first generation plastic photochromic ophthalmic lenses, the Transitions ® Comfort Lens, were manufactured in Ohio and test-marketed in June of 1989.
Scheme 17 136 Barry Van Gemert 3. However, in several cases, publications from as late as 1997 are included. The important design concepts of such truly advanced materials are discussed, their fabrication methods are emphasized, and their applications are highlighted. In this tragic death the world of photochromism has lost the person chiefly responsible for the success of the largest commercial application of organic photochromics. Guglielmetti Table of Contents Introduction 1.
Their probable structures have been estimated as per the basis of their spectroscopic data. This may be invoked to explain the unusual properties of the colored species of this series of compounds. Brief Historical Survey of Photochromism. Nature of the Closed Form. Bertelson Spiropyrans 41 42 Robert C.
Several others have shown considerable promise and may very well be utilized in commercial products in the future. An earlier goal of finding spiropyrans giving intense yellow, orange, and red colors while also having thermal fade rates, quantum yields, and fatigue rates very close to the available blue and green dyes has been mostly met by spirooxazines and chromenes that cover these regions of the spectrum. This light-assisted deposition is a useful method for preparing stable photosensitive films. In a less efficient route to the same material, 4-methoxyphenyllithium from the metallation of 4-bromoanisole was coupled with silica gel. Scheme 29 Cyanine dyes having a 2-hydroxyphenyl substituent on a β-position of the polymethine chain, proposed earlier 94 as salts of the open form of spiropyrans, have been prepared 95 and treated with base. In most cases the Robert C. Experiments showinga rapid and reversible change ofcolor s eem likemagic and are always fascinating.
Kraus, Professor Chemistry, Professor of Optics, The University of Rochester. The photochromic reactions are shown in Scheme 10. The nanocomposites exhibited excellent fluorescent thermo-switching action with respect to the free spiro molecule. A convenient synthesis of 3-alkyl-2,3-dimethylindolenines consists of treating the 2,3-dimethylindole with BuLi to give the Li salt, followed by addition of the alkyl iodide. While a 5-methoxy has no influence on the color of the open form, a 5-acetoxy and several related groups 42,43 results in a bathochromic shift in the case of acetoxy of 25 nm. The Bischler synthesis from a substitued aniline, and especially from anilines bearing one or more alkoxy groups, is much preferred in practice for indoles substitued in the 4—7-positions, since the substituted arylhydrazines needed for the Fischer synthesis are costly, unstable, or unavailable.
Spiropyran-modified artificial monolayer, bilayer, and multilayer membranes whose physical and chemical properties can be controlled by irradiation are discussed in Chapter 1 in Volume 2. The photochromic reactions are shown in Scheme 9. No triplet transient species was observed and oxygen had no effect on the transient spectra and kinetics of the photochromic reactions, Ilge and Paetzold 102 and Ilge et al. This worldwide curiosity can be exemplified by way of the authors of the chapters inside of this publication. Photochromic glasses that darken in the sunlight protecting eyes from excessive light intensity and bleach in dim light are today a part of everyday life.