Optical fulgides

The great merit of thermal irreversibility is the permanent nature of the states. Therefore, fulgides have long been viewed as potential candidates for photon-mode optical recording materials. In addition, fulgides have been used as prototypes to demonstrate their potential applicability as photoswitchable functional materials. Those switch models that had appeared up until the end of 1999 are described in this chapter. 

Switching of Non-linear Optical Properties through Fulgide Photochromism I 113... 

Fulgides have been extensively investigated as erasable and rewritable optical memory systems (see Chapter 4) and these photochromic molecules are attractive candidates for chiroptical switch development.1471 Their bistability is based on the... 

A quantitative study of the RISC quantum yield was carried out with 55 [37]. This study involved UV irradiation of 55 in benzene or cyclohexane solution to produce the 7, state and subsequent photolysis by a second laser tuned to the T-T absorption band. The second pulse was accompanied by depletion (bleaching) of the T-T absorption and 5, — S0 fluorescence [the fluorescence was detected and quantified by an optical multichannel analyzer (OMA)]. The quantum yield of RISC, d>RISC, was calculated using Aberchrome 540, a reversible fulgide, as a two-laser actinometer. The values for benzene solvents, respectively. This compares with 0.19 found for 55 in ethanol solvent [36]. 

Fulgides and spiropyranes as materials able to reversible photocycliza-tion-decyclization, allowing storage of optical data 93T8267. 

Fulgides and fulgimides - potentially useful for information storage in erasable optical disks ... 

Chapter 4 (Fulgides). The fiilgides are a class of photochromic compounds for which the thermal reversal or decoloration of the colored species is disallowed. Therefore, the reversion is largely driven photochemically as is illustrated with compound 4 (Scheme 4). Because of the stability of the colored species toward thermal reversion, the fulgides have potential application in the field of optical storage and security printing. Another use, in actinometry, is well known. 

Based on the five classes of fulgide family compounds, many realistic and potential applications have been developed and suggested for example, actinometry, optical storage, optical data processing, and nonlinear optical materials, optical waveguides, optical switches, security and printing applications, eyewear and leisure products. Applications of the fulgide family of compounds are discussed at the end of this chapter. 

According to laser photolysis results, the time scale of the coloration of heterocyclic fulgides is shorter than a few nanoseconds and extends to the picosecond time scale. The results indicated that the photoresponse of the photochromic optical disk could be very fast. 

How can nondestructive readout be obtained It is still a serious question. There are several ways to try. Matsui et al.107 presented a fundamental idea for a nondestructive readout method based on finding the wavelength dependence of the bleaching quantum yield of the colored form of the fulgide. An optical disk sample with photochromic compound 56d has been made. The photochromic reactions are shown in Scheme 41. 

S. Goldschmidt, R. Riedle, and A. Reichardt, Bisbiphenylene fulgides and the cleavage of disbiphenylene fulgenic acid to optically active components, Ann., 604, 121-132 (1957). 

A. P. Glaze, H. G. Heller, and J. Whittall, Photochromic heterocyclic fulgides. Part 7. (E)-Adamantylidene-[1 -(2,5,-dimethyl-3-furyl)ethylidene] succinic anhydride and derivatives Model photochromic compounds for optical recording materials, J. Chem. Soc., Perkin. Trans. 2, 1992, 591-594. 

Y. Yokoyama and Y. Kurita, Photochromic fulgides applicable to optical information storage, discovery of new nondestructive readout method, J. Chem. Soc. Jpn., Chem. Indus. Chem., 1992, 998-1006. 

F. Matsui, H. Taniguchi, Y. Yokoyama, K. Sugiyama, and Y. Kurita, Application of photochromic 5-dimethylaminoindolyl fulgide to photon-mode erasable optical memory media with non-destructive ability based on wavelength dependence of bleaching quantum yield, Chem. Lett., 1994, 1869-1872. 

The racemization is not acceptable when chiral fulgides are used as the optical switches. If a photochemically as well as thermally stable intrinsic chirality is... 

Kurita, S. Takeda, J. Yokoyama, Y. Kurita, Y. Photochromic Fulgides Applicable to Optical Information Storage Tsuruta, T, Ed. Elsevier Amsterdam, 1993 Vol. C, pp. 357- 362. 

Fulgides and related diarylethenes have been investigated extensively because of the long-term thermal stability of their photocyclized colored forms, which could lead to this application in erasable optical recording materials and photoswitchable optical elements. The entrapment of these photochromic molecules in polymer films is necessary for these practical applications. Picosecond laser photolysis was employed to study the electrocyclic reaction of a furylfulgide (18, Figure 8) in polymer solids and revealed that the colored structure was formed with a time constant of ca. lOps irrespective of the nature of the polymer matrix.49... 

A patent has been lodged dealing with the synthesis of optically active binaph-thol-condensed fulgides. New photochromic polymers have been synthesized... 

Yu et al. [36] have reported applications of pyrryl fulgides with respect to optical data storage. More than 500 UV-irradiation and photobleaching (He-Ne laser, 632.8 nm) cycles of an optical disk coated with PMMA thin film doped with pyrryl fulgide without fatigue resistance of formation photodecomposed species were demonstrated. 

Chiroptical molecular switches (photochromic compounds among them dihetarylethenes, fulgides, and spiropyrans permitting undestructive read-out of information using change of optical rotation 00CRV1789. 

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