Spirobenzopyran Derivatives

3 Chemical structure of spirobenzopyran.Parts A and B are spirobenzopyran isomers. 

4 Absorption spectra of polystyrene film containing spirobenaopyran before (A) and after (B) 442-nm light exposure. 

5 Optical system for readout of 3D memory. For nondestructive readout, a near-IR differential phase-contrast microscope is used. 

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8 Photochramic reactions of (a) l,2-bis-(2-meth)rM-benzothiophen-3.yl)perfluorocydof en-tene, and (b) 2- l,2-dimethyi-3-indolyt)-3-(2,4,5-trimethy. 3-thienyl)maleic anhydride. 

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It was only recently that these phenomena were detected photochemically using photochromic molecules whose chromophores undergo a reversible photoisomerization reaction. The photochemical reactions involved in these processes are mainly the trans-ds isomerization of aromatic azo compounds and stilbene derivatives as well as the ring opening/dosure reaction of spirobenzopyran derivatives . ... 

Spirobenzopyran derivatives were used as media of wavelength-multiplexed memory. A narrow absorption spectrum is required for the wavelength multiplex. The narrow spectrum was obtained by using J-aggregates of spirobenzopyrans. The J-aggregates have an absorption peak width of a few dozen nanometers. A five-wavelengths-multiplexed memory was demonstrated, but considerably large crosstalk between multiplexed channels was observed. ... 

Anzai J I, Osa T. 1994. Photosensitive artilidal membranes based on azobenzene and spirobenzopyran derivatives. Tetrahedron 50(14) 4039 4070. 

The photochromic behavior of spirobenzopyran derivatives has been investigated by many researchers. The spirobenzopyran molecnle nnderwent reversible photochemical cleavage of the C-O bond. The componnd is stable in its closed form, and its solution is colorless. Another interesting featnre of the photoindnced reaction is that UV irradiation indnces electric charges in the open form of the molecnle. 

Spiroindolinobenzothiopyrans can be prepared by condensation of Fischer s base with thiosalicylaldehyde derivatives 46 in ethanol, as shown in Scheme 22.71,89 93 Reaction of 1,2,3,3-tetramethylindolinium salt with carbamoylthiobenzaldehyde,92 which is an intermediate for preparation of thiosalicylaldehyde, also gives the spirobenzothiopyran in high yield via the corresponding indolinium salt, as shown in Scheme 22.94 Conversion of spirobenzopyrans to the corresponding spirobenzothiopyran by phosphorous pentasulfide in pyridine or xylene is possible, but the purification of the product is difficult. 

Fig. 2. Stereoisomers of merocyanine derived from X-substituted l-alkyl-3,3-dimethylindolino-spirobenzopyran...

Most striking is however the dependence of the rate of bleaching in the neighborhood of the glass transition temperature of the copolymers. This dependence is illustrated in Tables 5 and 6 for methacrylic copolymers carrying spirobenzopyran and azo side groups, respectively. In these experiments the spirobenzopyran comonomer was methacryloylaminoethyl)-6 -nitro-DIPS (IX) and the azo derivative comonomer 4-methacryloylaminoazobenzene (IV). 

Besides azobenzene, spirobenzopyran, and salicylidene derivatives, other photochromic dyes have been used in LBK films. For example, anthocyanine dyes 5 (see Figure 6.5) have been used to obtain monolayers that change the area at constant pressure upon irradiation. Diphenyldiacetylerie chromophores 6 (Figure 6.5) have shown photoinduced anisotropy upon polar-... 

The V1/2 values obtained for dioxane solutions (10 4M) of spirobenzopyrans substituted on the chromene moiety are presented in Table 2. In the nitro-substituted spiropyran series (6, 28, and 29), the 6-nitro derivative is usually more stable. OCH3 and CHO substituents are also more stabilizing when on C6 (cf. 6 and 32 30 and 32). Indeed, the electron-donor efficiency of the methoxy group is higher when at C6 as indicated by the Hammett ct constant values, which are -0.76 for the C6 (para) position and -0.39 for the C8 (ortho) position. For the nitro-substituted spiropyrans, the electron-withdrawing character of N02 depends on the substitution position, with Hammett constants of 0.66, 0.78, and 0.80, for N02 at C7, C6, and C8, respectively. 

Three-dimensional optical data storage using photochromic materials (spirobenzopyrans, dihetarylethenes, azobenzene derivatives 00CRV1777. 

Kimura et al. [259] reported applying organic photochromic compoimds to photochemical switching of metal-ion complexation and ionic conduction by combining photochromism with metal-ion binding property of crown ether derivatives. They synthesized vinyl polymers, incorporating a crowned spirobenzopyran moiety at the side chain ... 

Two types of cteviation from the first-orda kinetics are noted for photo-aialthamal isomerization reactions in polymer films. The first is the normal type, in which the reaction rate is the same as or smaller than that in solutions at the initial stage and then progressively becomes smaller. Typical examples are thermal decoloration of the photocolored merocyanine form of spirobenzopyran molecularly dispersed in or chemically bound to a polymer matrix > and photoisomerization of the transazobenzene residue incorporated in polymer main chains The first interpretation for the decoloration of the merocyanine form assumed the existence of different isomers, each of which fades independently following first-order kinetics On the other hand, Kryszewski et al. proposed the kinetic matrix effect, which means that the distribution of free volume may lead to the deviation from first-order kinetics. His idea was based on the finding that deviations from first-order kinetics can be observol even in simple molecules such as azobenzene which has only one trans or cis isomeric form. The effect of free volume distribution on reactivity was further demonstrated by studies of annealed polymer films The distribution function of free volume as well as the critical free volume v were estimated for the merocyanine form of spiropyran in poly(methyl methacrylate) derivatives of azobenzene in polystyrene and azobenzene in polycarbonate The deviation from first-order kinetics was also observed in cyclizing imidization of model poly(amic acid) in a polyamide matrix... 

Therefore, the chemical linking of the dye molecules is only worthwhile if it results in a substantially better performance of the resulting materials. For the reasons discussed below, this is mainly expected for nonlinear optics (NLO) dyes. However, other dye-containing materials were also prepared by this approach. For example, new transparent photochromic hybrid materials were prepared by sol-gel processing of Si(OEt)4, sUanol-terminated dimethylsiloxane oligomers and triethoxysilylpropyl-substituted spirobenzopyranes, and fluorescent glasses and films from pyrene derivatives covalently tethered to RS103/2 (R = alkyl, phenyl) . 

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