Diarylethene derivatives

B1536 is a yellow isomer that is converted into a red isomer upon irradiation with 380 nm light. The written data can be erased by irradiation with 543 nm light. This photochromic material (B1536) did not exhibit any apparent fatigue even after 100 write/erase cycles the written data (i.e., the red isomer) were stable at 80°C for more than three months, and thermal back reaction (from the red isomer to the yellow isomer) did not occur even at 200°C.  

For recording, a two-photon process at the focused spot was used in order to access a point in a thick medium. A Ti sapphire laser at 760 nm 

9 (A) Chemical structure of cis-l,2 diciano-i,2-bis(2,4,5-trimeti. 3-thienyl)ethene (BI536) and (B) its absorption spectra. 

10 Readout of bit patterns written into photochromic memory using a diaryiethene derivative.The data were read out with a reflection confocal microscope.  

NM 2 (A) Chemtcalstructure t f-ur Sl aneHjret eopofynte- aiHl ( ) hs absorjwton specffwn. 

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Masahiro Irie received his B.S. and M.S. degrees from Kyoto University and his Ph.D. in radiation chemistry from Osaka University. He joined Hokkaido University as a research associate in 1968 and started his research on photochemistry. In 1973 he moved to Osaka University and developed various types of photoresponsive polymers. In 1988 he was appointed Professor at Kyushu University. In the middle of the 1980 s he invented a new class of photochromic molecules - diaryl-ethenes - which undergo thermally irreversible and fatigue resistant photochromic reactions. He is currently interested in developing singlecrystalline photochromism of the diarylethene derivatives. 

Yamamoto, S., Matsuda, K., and Irie, M. (2003) Absolute asymmetric photocyclization of a photochromic diarylethene derivative in single crystals, Angew. Chem. Int. Ed., 42, 1636-1639. 

Such thermally irreversible photochromic chromophores represent the other class, classified as P-type (photochemically reversible type). Although many photochromic compounds have been so far reported, P-type chromophores are very rare. Only two families, furylfulgide derivatives and diarylethene derivatives, exhibit this reactivity.19 101 The photogenerated isomers of these derivatives are thermally stable and never revert to their initial isomers even at elevated temperatures (-100 °C). The thermally stable photochromic compounds offer potential for various applications in photoswitching and memory devices. 

The primary difference, for our purposes, between furylfulgide derivatives and diarylethene derivatives is fatigue resistance. Diarylethenes have high durability col-... 

Properties which change concomitantly with diarylethene derivative photoisomerization are geometrical structures, electronic structures, refractive indices, and chiral properties (when the molecules have chiral substituents). Table 1 shows how the above property changes are applied to various photoswitching molecular systems. Details of these photoswitching functions are described in Sections 2.3 to 2.6. 

Figure 1 shows a typical diarylethene derivative absorption spectral change.1121 Upon irradiation with 313 nm light, a colorless hexane solution of l,2-bis(2,4-dimethyl-5-phenylthiophen-3-yl)perfluorocyclopentene la turned blue, in which an absorption maximum was observed at 562 nm. 

The blue color was disappeared by irradiation with visible (X > 500 nm) light. In the dark, however, the blue color remained stable and at room temperature never reverted to the colorless form. In toluene, the colored isomer was found to be stable even at 100 °C. The stable, colored isomer was isolated by HPLC and its molecular structure was analyzed by NMR and X-ray crystallography. Both indicated that the blue colored isomer was the closed-ring form. Therefore, the photochromism of the diarylethene derivative was ascribed to the following photocydization and cycloreversion reactions. 

Some diarylethene derivatives that possess strongly electron-withdrawing substituents deviate from the general ruleJ5,23 The closed-ring isomers of 12b and 13b, possessing dicyanoethylene substituents, reverted to the open-ring isomers in 3.3 min and 186 min, respectively, at 60 °C. The dithienylethenes 14b, with pyridinium ion substituents, and 15b, with formyl residues, also underwent thermally reversible photochromic reactions. 

A sol-gel technique was used to prepare hybrid organic-inorganic xerogels containing high concentrations of dithienylethenes. The sol-gel materials were prepared by a method based on co-condensation between the hydrolyzed species of the diarylethene derivative 38a and of methyltrihydroxysilane precursors as shown below. 

Scheme 14 Diastereoselective photocyclization of chiral diarylethene derivative 27.

Scheme 9.4 Syntheses of diarylethene derivatives using the common diiodo intermediate. Reagent and conditions (a) l2, H5IOe, H2S04, AcOH, H20, 76% (b) Pd(PPh3)4, 4-formylphenylboronic acid, Na2C03, THF, H20, 49% (c) fl-BuLi, B(OBu)3 then Pd(PPh3)4, 4-formyl-4 -iodobiphenyl,...

In this section, we propose a new switching unit, in which two radicals are placed in the same aryl unit and Jt-conjugated chain is extended from 2- and 5-positions of the thiophene ring in one aryl unit of the diarylethene [70]. The photochromic reactivity and magnetic switching of the new diarylethene derivatives will be discussed. 

As a typical example of diarylethene derivatives, the procedure for the synthesis of diarylethene biradical 10a [37] is given below. 

Novel Ag1 coordination polymers with a diarylethene derivative, cis-dbe, have been synthesized by Munakata et al. [31]. Polymers with a onedimensional infinite chain structure, 33, and another with a two-dimensional sheet structure, 34, were synthesized and their reversible photoreactions with 450 nm and 560 nm light in the solid state were revealed. 

M. Irie and M. Mohri, Thermally irreversible photochromic systems. Reversible photocyclization of diarylethene derivatives, J. Org. Chem. 53, 803-805 (1988). 

K. Uchida, S. Nakamura, and M. Irie, Photochromism of diarylethene derivatives. Stability of the closed-ring forms, Res. Chem. Intermed. 21, 861-876 (1995). 

Y. Nakayama, K. Hayashi, and M. Irie, Thermally irreversible photochromic systems. Reversible photocyclization of nonsymmetric diarylethene derivatives, Bull. Chem. Soc. Jpn. 64, 789-795 (1991). 

As in previous years, thiophene based diarylethene derivatives constitute an important class of materials which are considered as promising candidates for various kinds of optoelectronic devices, such as switches and optical memories. 

Various materials have been examined for the media of near-field recording, Martin el al and Betzig et used optomagnetic material, and Irie used diarylethene derivatives. ... 

Hoshino, M., Ebisawa, F., Yoshida, T., and Sukegawa, K. Refractive index change in photochromic diarylethene derivatives and its application to optical switching devices. J. Photochem. Photobiol. A Chem. 1997, 105, 75. 

For any application of photochromic molecules, a discussion of the thermal stability of the colored form is in order. We will discuss two types of photochromic molecules (1) those that operate by a photon-heat mode (photochemical forward reaction and a thermal reverse reaction), such as spiropyran derivatives, and (2) those that exhibit a photon-photon mode, such as diarylethene derivatives. 

The second category of compounds—those operating by a photon-photon mode—comprises photochromic systems functioning photochemically in both the forward and backward reactions. Fulgide and diarylethene derivatives are representative examples (Scheme 1). 

Diphenylcarbene also undergoes effective addition to various 1,1-diarylethene derivatives. Thus, irradiation of a benzene solution of diphenyldiazomethane and l,l-bis(4-phenoxy-phenyl)ethene yielded l,l-bis(4-phenoxyphenyl)-2,2-diphenylcyclopropane(3f) in 69% yield. " ... 

Professor at Kyushu University. In the middle of the 1980 s he H invented a new class of photochromic molecules - diaryl-ethenes - which undergo thermally irreversible and fatigue resistant photochromic reactions. He is currently interested in developing singlecrystalline photochromism of the diarylethene derivatives. 

Figure 23.2 Diarylethene derivatives that show photochromism in the crystalline phase.

Figure 23.3 Photochromism of diarylethene derivatives in the single-crystalline phase.

Why is the thermal stability of diarylethene derivatives enhanced by replacing phenyl groups with furan or thiophene groups In molecular orbitals calculation, the photochromic reaction is treated as a typical electrocyclic reaction between hexatriene and cyclohexadiene. The thermal reaction proceeds disrotatorily and the photoreaction, conrotatorily. Disrotatory cyclization of A to B requires an increase in free energy larger than 138 kJ/mol, and hence no thermal ring-closure occurs in the case of either phenyl- or furan-substituted molecules (see... 

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