- Spectroscopic, photochromic and kinetic behavior of photo conversion of Aberchrome 540 in an ionic liquid media
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The photo-bleaching reaction of the chemical actinometer, Aberchrome 540, is reported for the first time in a series of ionic liquids (ILs). This fulgide in its C-form undergoes an opening reaction to yield its E-form, when it is irradiated with UV light at wavelengths >400 nm. The magnitude of bleaching was monitored spectrophotometrically and their kinetics evaluated, obtaining first-order rate constants (kobs). The results obtained in different ILs suggest that changes in the rate constants (kobs) of the opening reaction of Aberchrome 540 are mainly governed by weaker interactions such as coulombic (π* parameter) and Van der Waals interactions (δH 2, parameter). In addition, the photochemical fatigue resistance was also studied in ILs media and compared with conventional solvents (benzene, toluene, etc.). In particular, we found that three different tendencies dependent on the ILs used exist. The first group of ILs where the reversibility of the fulgide is favored (for example, [Bmim][BF4], [Bmim][PF6] and [Bmim][OTf]), behaviour similar to conventional solvents. The second group corresponds to ILs where photo reversibility is partial; and finally, other group of ILs that prevented photo reversibility. It is proposed that depending on the ILs used, the stabilization of different forms of the fulgide can be controlled, thus resulting important in terms of choosing the appropriate ILs for a specific photochemical reaction.
- Aliaga,Pavez G,De la Fuente,Nú?ez,Ca?ete
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- Photochromic Heterocyclic Fulgides. Part 3. The Use of (E)-α-(2,5-Dimethyl-3-furylethylidene)(isopropylidene)succinic Anhydride as a Simple Convenient Chemical Actinometer
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The thermally stable photochemically fatigue resistant title compound and its coloured form provide a photochromic system well suited for chemical actinometry in the near-u.v. and visible spectral regions.A solution of the photochromic compound in many common organic solvents can be used repeatedly and, provided the stirred solution absorbs all the incident radiation, the radiant flux can be determined simply by measuring an absorbance change.
- Heller, Harry G.,Langan, John R.
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- Ultrafast laser spectroscopic study on photochromic cycloreversion dynamics in fulgide derivatives: One-photon and multiphoton-gated reactions
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Cycloreversion processes of three photochromic fulgide derivatives in toluene solution were investigated by means of picosecond and femtosecond laser photolysis methods. Femtosecond laser irradiation revealed that the cycloreversion processes upon visible one-photon excitation took place within a few ps in these three derivatives. On the other hand, drastic enhancements of the reaction yield were observed under picosecond laser exposure. Excitation intensity effect of the reaction yield and dynamic behaviors revealed that the successive two-photon absorption process leading to higher excited states opened the efficient cycloreversion channel in the three derivatives. The reaction yields in higher excited states were found to be quite large in these three systems, 0.35-0.55, while those in the S1 state were 0.048-0.21. The correlation of the reaction yield in the S1 state with that in S n states suggest the character of the electronic states connected by the optical absorption plays an important role in the control of the cycloreversion reaction. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2009.
- Ishibashi, Yukihide,Katayama, Tetsuro,Ota, Chikashi,Kobatake, Seiya,Irie, Masahiro,Yokoyama, Yasushi,Miyasaka, Hiroshi
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- Photochromism of a Furylfulgide, 2--3-isopropylidenesuccinic Anhydride in Solvents and Polymer Films
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The quantum yields of the photochromic reaction between (E)- and (Z)-2--3-isopropylidenesuccinic anhydride and the cyclized valence isomer were determined in various solvents and polymers.In both media the ring-opening quantum yield (ΦCE) depended on the dielectric constant of the media.In some polymer films, ΦCE were larger, and the cyclization quantum yield (ΦEC) and olefinic isomerization quantum yields (ΦEZ and ΦZE) were smaller than those in the corresponding solvents.
- Yokoyama, Yasushi,Hayata, Hirofumi,Ito, Hiroshi,Kurita, Yukio
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- Effects of Steric Bulkiness of Substituents on Quantum Yields of Photochromic Reactions of Furylfulgides
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Furylfulgides with different sizes of alkyl substituents were synthesized and their photochromic properties were examined. While the quantum yield of coloring reaction increased and the quantum yield of the E-to-Z isomerization decreased as the steric bulkiness of the alkyl substituent on the 2,5-dimethyl-3-furylmethylidene moiety increased, the bleaching quantum yield increased as the isopropylidene group was replaced by an adamantylidene group. Both effects worked independently, and a furylfulgide with an isopropyl group on the furylmethylidene moiety and an adamantylidene group in one molecule showed the coloring quantum yield of 0.51 (366 nm) and the bleaching quantum yield of 0.26 (492 nm) in toluene.
- Yokoyama, Yasushi,Inoue, Tetsushi,Yokoyama, Masato,Goto, Takakazu,Iwai, Takeshi,et al.
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- Synthesis and photochromic properties of fulgides with a t-butyl substituent on the furyl- or thienylmethylidene moiety
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2,6,6-Trimethyl-5-(2,5-dimethyl-3-furyl and -3-thienyl)-3-heptyn-2,5-diols were carbonylated in benzene in the presence of 1:1 - Pd(OAc)2/I2 as the catalyst. The reaction at 90°C under 80 atm of carbon monoxide for 5 h directly gave both E and Z isomers of t-butyl-substituted furyl- or thienyl fulgides. The former had been reported impossible to synthesize by the Stobbe condensation. Similarly, furyl- and thienylfulgides with an isopropyl group were synthesized by this method. The fulgides were isolated by column chromatography in 37-75% yields. Coloring quantum yields of t-butyl-furyl- and -thienylfulgides are 0.79 and 0.73, respectively, which are the greatest in each series of fulgides with the same heteroaromatic ring.
- Kiji,Okano,Kitamura,Yokoyama,Kubota,Kurita
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- Dynamics of the cyclization reaction in photochromic furyl fulgides
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The dynamics of the photoinduced cyclization reaction of furyl fulgides has been studied applying femtosecond time-resolved transient absorption spectroscopy. For furyl fulgide 1 and adamantylidene-substituted furyl fulgide 2 in different solvents, a scheme of the reaction mechanism is set up and the reaction rates are determined by fitting individual transients. Two parallel reaction pathways can be distinguished, one of them including an intermediate state. Reaction times in the picosecond range support the application of fulgides in optical data storage media and as molecular photoswitches.
- Handschuh,Seibold,Port,Wolf
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- X-ray diffraction analysis of photochromic reaction of fulgides: Crystalline state reaction induced by two-photon excitation
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Although most fulgides show their photochromism in the solid state, crystal structure changes accompanying the photochromism have not been previously observed. The photochromic reactions have been so far considered to take place on surfaces or at defects of the crystals or to proceed with destruction of the crystals. In this study we have succeeded in observing crystal structure changes accompanying the photochromism of fulgides using X-ray diffraction analysis. Detection of the photoproducts in the crystal structures was not possible when the single crystals of the fulgides were irradiated with steady UV light. Two-photon excitation by pulsed laser light was essential to produce a sufficient amount of the photoproducts without significant deterioration in the quality of the crystals.
- Harada, Jun,Nakajima, Ryo,Ogawa, Keiichiro
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- Photomechanical motion of furylfulgide crystals
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Plate-like microcrystals of a photochromic furylfulgide bend toward the light upon UV irradiation and then straighten upon visible light irradiation. The reversible bending was observed over 200 cycles of alternating irradiation with UV and visible light. The mechanism of bending could be explained by the X-ray crystallographic data.
- Koshima, Hideko,Nakaya, Hidemitsu,Uchimoto, Hidetaka,Ojima, Naoko
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- Photochromism of rotation-hindered furylfulgides influenced by steric modifications
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The syntheses of a bicyclic furylfulgide 14 and a (benzofuryl)fulgide 15 with increased steric constraints are described. Their photochromic behaviors were analyzed by means of UV/Vis spectroscopic measurements, X-ray crystallography, and NMR experiments, and the results were compared to those of the furyl(methyl)fulgide 12 and the furyl(isopropyl)fulgide 13. Compounds 13E and 14E exhibit large quantum yields of 0.57 and 0.53 for the coloration reaction (E) → (C) compared with 12E and 15E (0.23 and 0.17). After irradiation with 350 nm light, 13E and 14E are transformed into the closed (C) forms almost quantitatively, whereas 12E and 15E result in a photostationary state with mixtures of the (E), (Z), and (C) forms. The crystal structures obtained for 13E, 14E, and 15E show that the fulgides adopt cyclizable helical (P)-Eα conformations with no significant differences in atomic distances in the hexatriene unit. 2D- and temperature-dependent NMR experiments showed that the enantio- and diastereotopomerization processes were suppressed in a fulgide for the first time. Compound 14E populates only the E α conformational state. In contrast, 13E and 15E both exist in the cyclizable Eα and the non-cyclizable Eβ conformations in solution. Due to the annulated benzene ring, 15E exhibits a higher thermodynamic barrier than 13E, so the "belly roll" process was reduced for 15, but the (E) → (Z) isomerization could not be suppressed. The structural modification of 14 successfully suppressed the (E) → (Z) isomerization as well as the belly roll process. The way in which the isomerization reaction is suppressed by steric hindrance could not be fully elucidated by using these methods. Copyright
- Struebe, Frank,Siewertsen, Ron,Soennichsen, Frank D.,Renth, Falk,Temps, Friedrich,Mattay, Jochen
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p. 1947 - 1955
(2011/04/27)
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- Synthesis and photochromism of 1,2-bis(5-aryl-2-phenylethynylthien-3-yl)hexafluorocyclopentene derivatives
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Photochromic dithienylethenes that possess elements of lipid complementarity, and undergo large, photoinduced changes in molecular geometry have been prepared. Further, a regioselective approach has been developed for the preparation of dithienylethenes containing phenylethynyl and various aryl substituents at C2 and C5 of the thiophene moieties, respectively. The prepared photochromic compounds were observed to undergo reversible photoisomerization. Their absorption properties, reaction quantum yields, and photoconversions were determined in n-hexane.
- Cai, Jianxin,Farhat, Amani,Tsitovitch, Pavel B.,Bodani, Vivek,Toogood, R. Daniel,Murphy, R. Scott
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experimental part
p. 176 - 182
(2010/11/05)
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- Steric Effect of Alkylidene Groups of Furylfulgides on the Photochromic Behavior
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Photoreactions of furylfulgides having a large alkylidene group (7-norbornylidene or 2-adamantylidene) were investigated.An adamantylidene fulgide with propylidene group recorded 0.51 and 0.26 for coloring and bleaching quantum yields, respectively.
- Yokoyama, Yasushi,Iwai, Takeshi,Kera, Naohiko,Hitomi, Isamu,Kurita, Yukio
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p. 263 - 264
(2007/10/02)
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- Fulgides as Efficient Photochromic Compounds. Role of the Substituent on Furylalkylidene Moiety of Furylfulgides in the Photoreaction
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Quantum yields of photoreactions of furylfulgides having Me, Et, n-Pr, or i-Pr on the furylalkylidene moiety were measured.The E-Z isomerization was greatly suppressed and the cyclization was accelerated when the alkyl group (R) became bulkier.When R was i-Pr, no E-Z isomerization was observed and the quantum yield of the colorizing cyclization was 0.62.
- Yokoyama, Yasushi,Goto, Takakazu,Inoue, Tetsushi,Yokoyama, Masato,Kurita, Yukio
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p. 1049 - 1052
(2007/10/02)
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- Photochromic Heterocyclic Fulgides. Part 2. Electrocyclic Reactions of (E)-α-2,5-Dimethyl-3-furylethylidene(alkyl-substituted methylene)succinic Anhydrides
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The pale yellow title compounds undergo reversible photochemical conrotatory electrocyclic reactions to give in quantitative yields deep red 7,7a-dihydrobenzofuran-5,6-dicaroxylic anhydrides, which are stable at 100 deg C.These photochromic systems, which have high quantum yields for photocolouration, are highly resistant to photodegradation and retain their photochromic properties in a variety of solvents.
- Darcy, Paul J.,Heller, Harry G.,Strydom, Peter J.,Whittall, John
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p. 202 - 205
(2007/10/02)
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