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Masahiro Irie - One of the best experts on this subject based on the ideXlab platform.
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dynamics of cyclization cycloreversion and multiphoton gated reaction of a photochromic diarylethene derivative in Crystalline Phase
Journal of Physical Chemistry C, 2008Co-Authors: Kensuke Tani, Seiya Kobatake, Hiroshi Miyasaka, Yukihide Ishibashi, Masahiro IrieAbstract:Cyclization and cycloreversion reactions of a photochromic diarylethene derivative, bis(2-methyl-5-phenylthiophen-3-yl)perfluorocyclopentene, in Crystalline Phase were investigated by means of picosecond laser spectroscopy. Rapid cyclization within a few picoseconds, as comparable to that in solution Phase, was confirmed for the colorization reaction in the Crystalline Phase. On the other hand, cycloreversion reaction took place with a time constant of 25 ps. In addition, nonlinear enhancement of the cycloreversion process was observed. The excitation intensity dependence of the reaction profiles and the correlation of the apparent reaction yield with the time interval of two pulses employed for the excitation clearly revealed that the successive two-photon absorption process via the S 1 state, leading to higher excited states, opened the efficient cycloreversion process. The dynamics and mechanisms of the multiphoton-gated reaction in the Crystalline Phase were discussed by comparing the present results ...
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photochromism of 1 2 bis 2 ethyl 5 phenyl 3 thienyl perfluorocyclopentene in a single Crystalline Phase conrotatory thermal cycloreversion of the closed ring isomer
Journal of the American Chemical Society, 2000Co-Authors: Seiya Kobatake, Katsunori Shibata, And Kingo Uchida, Masahiro IrieAbstract:1,2-Bis(2-ethyl-5-phenyl-3-thienyl)perfluorocyclopentene (1a) was found to undergo a thermally reversible photochromic reaction in solution as well as in the single-Crystalline Phase. Upon irradiation with ultraviolet light the hexane or toluene solution containing 1a and single-crystal 1a turned blue along with the formation of closed-ring isomer (1b). The blue solution and single crystal returned colorless by irradiation with visible light (λ > 500 nm) or heating above 100 °C. The bleaching is due to the cycloreversion of 1b to 1a. The thermal cycloreversion activation energies were measured in the toluene solution and in the single-Crystalline Phase above 100 °C. The activation energy from photogenerated 1b to 1a in the solution was 128 kJ mol-1, while it decreased to 120 kJ mol-1 in the crystal of the open-ring isomer 1a. In the crystal of the closed-ring isomer 1b the energy increased to 137 kJ mol-1. The cycloreversion reaction was found to be controlled by the environmental conditions. The thermal ...
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reversible diastereoselective photocyclization of a diarylethene in a single Crystalline Phase
Journal of the American Chemical Society, 2000Co-Authors: Tetsuhiro Kodani, And Seiya Kobatake, Kenji Matsuda, Taro Yamada, Masahiro IrieAbstract:Optically active photochromic (S)- and (R)-1-(2-methyl-5-phenyl-3-thienyl)-2-[2-(3-methyl-1-penten-1-yl)-5-phenyl-3-thienyl]-3,3,4,4,5,5-hexafluorocyclopentenes ((S)-1a and (R)-1a) were synthesized. X-ray crystallographic measurement showed that (S)-1a and (R)-1a single crystals adopted orthorhombic chiral space group P212121 and the open-ring isomers were packed in the crystals in only one conformer of the possible two atropisomers. Upon irradiation with 366 nm light (S)-1a and (R)-1a underwent reversible photocyclization reactions both in solution and in the single-Crystalline state, and in the Crystalline Phase almost only one closed-ring diastereomer was produced, while the diastereoselection was not observed in solution. The dominant diastereomer produced from (S)-1a was determined to be (S,R,R)-1b by X-ray crystallographic analysis.
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photochromism of 1 2 bis 2 methyl 5 phenyl 3 thienyl perfluorocyclopentene in a single Crystalline Phase
Journal of the American Chemical Society, 2000Co-Authors: Masahiro Irie, Thorsten Lifka, And Seiya Kobatake, Nobuo KatoAbstract:1,2-Bis(2-methyl-5-phenyl-3-thienyl)perfluorocyclopentene (1a) and their derivatives, 1,2-bis(2-methyl-5-p-tolyl-3-thienyl)perfluorocyclopentene (2a) and 1,2-bis(2-methyl-5-p-tert-butylphenyl-3-thienyl)perfluorocyclopentene (3a), were found to undergo reversible photochromic reactions in the single-Crystalline Phase. Upon irradiation with 366 nm light the single crystals turned blue. The blue colored crystals returned to colorless by irradiation with visible light (λ > 480 nm). The substituents at para positions of the phenyl groups did not affect the rates of photocyclization reactions both in the single-Crystalline Phase and in hexane. Activation energies of the photocyclization reactions were almost zero. On the other hand, activation energies as much as 5−10 kJ mol-1 were observed in the photocycloreversion reactions in the single-Crystalline Phase. These values were smaller than those observed in solution, ca. 16 kJ mol-1. Slow thermal cycloreversion reaction of the closed-ring isomer (1b) was observ...
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photochromism of 1 2 bis 2 methyl 6 nitro 1 benzothiophen 3 yl perfluorocyclopentene in a single Crystalline Phase dichroism of the closed ring form isomer
Journal of the American Chemical Society, 1999Co-Authors: Seiya Kobatake, Taro Yamada, Motoki Yamada, Masahiro IrieAbstract:1,2-Bis(2-methyl-6-nitro-1-benzothiophen-3-yl)perfluorocyclopentene was found to undergo a reversible photochromic reaction in the single-Crystalline Phase. Upon irradiation with 366-nm light, the single crystal turned green with keeping the crystal shape. The colored crystal showed dichroism. When the crystal was rotated under polarized light, the color changed from yellow to blue. The yellow and blue colors were attributed to two perpendicular electronic transitions at 465 and 600 nm of the closed-ring form. The two transition moments coincide with the directions of short and long axes of the closed-ring form isomers, which were regularly packed in the crystal lattice.
Matthias Wuttig - One of the best experts on this subject based on the ideXlab platform.
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unique bond breaking in Crystalline Phase change materials and the quest for metavalent bonding
Advanced Materials, 2018Co-Authors: Min Zhu, Oana Cojocarumiredin, A M Mio, Jens Keutgen, Michael Kupers, Juyoung Cho, Richard Dronskowski, Matthias WuttigAbstract:Laser-assisted field evaporation is studied in a large number of compounds, including amorphous and Crystalline Phase change materials employing atom probe tomography. This study reveals significant differences in field evaporation between amorphous and Crystalline Phase change materials. High probabilities for multiple events with more than a single ion detected per laser pulse are only found for Crystalline Phase change materials. The specifics of this unusual field evaporation are unlike any other mechanism shown previously to lead to high probabilities of multiple events. On the contrary, amorphous Phase change materials as well as other covalently bonded compounds and metals possess much lower probabilities for multiple events. Hence, laser-assisted field evaporation in amorphous and Crystalline Phase change materials reveals striking differences in bond rupture. This is indicative for pronounced differences in bonding. These findings imply that the bonding mechanism in Crystalline Phase change materials differs substantially from conventional bonding mechanisms such as metallic, ionic, and covalent bonding. Instead, the data reported here confirm a recently developed conjecture, namely that metavalent bonding is a novel bonding mechanism besides those mentioned previously.
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impact of vacancy ordering on thermal transport in Crystalline Phase change materials
Reports on Progress in Physics, 2015Co-Authors: Karl Simon Siegert, Hanno Volker, C. Schlockermann, Felix R L Lange, Ernstroland Sittner, T Siegrist, Matthias WuttigAbstract:Controlling thermal transport in solids is of paramount importance for many applications. Often thermal management is crucial for a device's performance, as it affects both reliability and power consumption. A number of intricate concepts have been developed to address this challenge, such as diamond-like coatings to enhance the thermal conductivity or low symmetry complex super-structures to reduce it. Here, a different approach is pursued, where we explore the potential of solids with a high yet controllable degree of disorder. Recently, it has been demonstrated that an unconventionally high degree of structural disorder characterizes a number of Crystalline Phase-change materials (PCMs). This disorder strongly impacts electronic transport and even leads to disorder induced localization (Anderson localization). This raises the question how thermal transport is affected by such conditions. Here thermal transport in highly disordered Crystalline Ge–Sb–Te (GST) based PCMs is investigated. Glass-like thermal properties are observed for several Crystalline PCMs, which are attributed to strong scattering by disordered point defects. A systematic study of different compounds along the pseudo-binary line between GeTe and Sb2Te3 reveals that disordered vacancies act as point defects responsible for pronounced phonon scattering. Annealing causes a gradual ordering of the vacancies and leads to a more ‘crystal-like’ thermal conductivity. While both vibrational and electronic degrees of freedom are affected by disorder, the consequences differ for different stoichiometries. This opens up a pathway to tune electrical and thermal transport by controlling the degree of disorder. Materials with tailored transport properties may not only help to improve power efficiency and scaling in upcoming Phase-change memories but are also of fundamental interest in the field of thermoelectric materials.
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disorder induced localization in Crystalline Phase change materials
Nature Materials, 2011Co-Authors: Michael Woda, Peter Jost, Hanno Volker, C. Schlockermann, Theo Siegrist, P Merkelbach, Matthias WuttigAbstract:Phase-change materials are used in computer memories for their switching between amorphous and Crystalline Phases. However, even the Crystalline state shows disorder, with extremely small electron mean free paths. The discovery that, depending on annealing temperature, this disorder leads to a metal–insulator transition in the Crystalline Phase provides a completely new look at the transport properties of these compounds.
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Disorder-induced localization in Crystalline Phase-change materials.
Nature materials, 2011Co-Authors: Theo Siegrist, Hessel Volker, Haaf Volker, Philippe Jost, Michael Woda, C. Schlockermann, P Merkelbach, Matthias WuttigAbstract:Localization of charge carriers in Crystalline solids has been the subject of numerous investigations over more than half a century. Materials that show a metal-insulator transition without a structural change are therefore of interest. Mechanisms leading to metal-insulator transition include electron correlation (Mott transition) or disorder (Anderson localization), but a clear distinction is difficult. Here we report on a metal-insulator transition on increasing annealing temperature for a group of Crystalline Phase-change materials, where the metal-insulator transition is due to strong disorder usually associated only with amorphous solids. With pronounced disorder but weak electron correlation, these Phase-change materials form an unparalleled quantum state of matter. Their universal electronic behaviour seems to be at the origin of the remarkable reproducibility of the resistance switching that is crucial to their applications in non-volatile-memory devices. Controlling the degree of disorder in Crystalline Phase-change materials might enable multilevel resistance states in upcoming storage devices.
Calum J Drummond - One of the best experts on this subject based on the ideXlab platform.
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nonionic diethanolamide amphiphiles with isoprenoid type hydrocarbon chains thermotropic and lyotropic liquid Crystalline Phase behaviour
Physical Chemistry Chemical Physics, 2011Co-Authors: Sharon M Sagnella, Charlotte E Conn, Irena Krodkiewska, Calum J DrummondAbstract:The thermotropic and lyotropic liquid Crystalline Phase behaviour of a series of diethanolamide amphiphiles with isoprenoid-type hydrocarbon chains (geranoyl, H-farnesoyl, and phytanoyl) has been investigated. When neat, both H-farnesoyl and phytanoyl diethanolamide form a smectic liquid Crystalline structure at sub-zero temperatures. In addition, all three diethanolamides exhibit a glass transition temperature at around -73 °C. Geranoyl diethanolamide forms a lamellar Crystalline Phase with a lattice parameter of 17.4 A following long term storage accompanied by the loss of the glass transition. In the presence of water, H-farnesoyl and phytanoyl diethanolamide form lyotropic liquid Crystalline Phases, whilst geranoyl diethanolamide forms an L(2) Phase. H-farnesoyl diethanolamide forms a fluid lamellar Phase (L(α)) at room temperature and up to ∼ 40 °C. Phytanoyl diethanolamide displays a rich mesomorphism forming the inverse diamond (Q(II)(D)) and gyroid (Q(II)(G)) bicontinuous cubic Phases in addition to an L(α) Phase.
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nonionic diethanolamide amphiphiles with unsaturated c18 hydrocarbon chains thermotropic and lyotropic liquid Crystalline Phase behavior
Physical Chemistry Chemical Physics, 2011Co-Authors: Sharon M Sagnella, Charlotte E Conn, Irena Krodkiewska, Calum J DrummondAbstract:The neat and lyotropic liquid Crystalline Phase behavior of three nonionic diethanolamide amphiphiles with C18 hydrocarbon chains containing one, two or three unsaturated bonds has been examined. This has allowed the effect of degree of unsaturation on the Phase behavior of diethanolamide amphiphiles to be investigated. Neat linoleoyl and linolenoyl diethanolamide undergo a transition from a glassy liquid crystal to a liquid crystal at ∼−85 °C, while neat oleoyl diethanolamide undergoes a transition at ∼−60 °C to a liquid Crystalline material before re-crystallizing at −34 °C. Oleoyl diethanolamide then undergoes a third transition from a Crystalline Phase to a smectic liquid Crystalline Phase at ∼5 °C. In the absence of water, the transition temperature from a smectic liquid crystal to an isotropic liquid decreases with increasing unsaturation. The addition of water results in the formation of a lamellar Phase (Lα) for all three amphiphiles. The lamellar Phase is stable under excess water conditions up to temperatures of at least 70 °C. Approximate partial binary amphiphile-water Phase diagrams generated for the three unsaturated C18 amphiphiles indicate that the excess water point for each amphiphile occurs at ∼60% (w/w) amphiphile.
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monodisperse nonionic isoprenoid type hexahydrofarnesyl ethylene oxide surfactants high throughput lyotropic liquid Crystalline Phase determination
Langmuir, 2011Co-Authors: Celesta Fong, Sharon M Sagnella, Irena Krodkiewska, Asoka Weerawardena, Xavier Mulet, Josephine Chong, Calum J DrummondAbstract:The neat and lyotropic Phase behavior of eight new ethylene oxide amphiphiles (EO = 1−8) with a hexahydrofarnesyl chain (3,7,11-trimethyldodecyl) and narrow polydispersity (>98.5% purity) is reported. Below five EO units the behavior of the neat surfactants show only a glass transition, Tg ∼ −90 °C. Above four EO units, crystallization (Tcrys) and crystal−isotropic liquid (Tm) transitions are also observed that increase with degree of ethoxylation of the surfactant headgroup. The lyotropic liquid Crystalline Phase behavior spans a complex spectrum of surfactant−water interfacial curvatures. Specifically, inverse Phases are present below ambient temperatures for EO < 4, with HFarn(EO)2 exhibiting an inverse hexagonal (HII) Phase stable to dilution. The Phase diagram of HFarn(EO)3 displays both the gyroid (Ia3d) and double diamond (Pn3m) inverse bicontinuous cubic Phases, with the latter being thermodynamically stable in excess water within the physiological regime. There is a strong preference for planar b...
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how chain length headgroup polymerization and anomeric configuration govern the thermotropic and lyotropic liquid Crystalline Phase behavior and the air water interfacial adsorption of glucose based surfactants
Langmuir, 2000Co-Authors: Ben J Boyd, Irena Krodkiewska, Calum J Drummond, Franz GrieserAbstract:A matrix of anomerically pure glucose-based surfactants have been synthesized and their thermotropic and lyotropic liquid Crystalline Phase behavior, and air-aqueous solution interfacial adsorption were investigated. The surfactants, which represent the major components of the Fischer synthesis products, were the n-octyl, n-decyl and n-dodecyl homologues of alkyl α-d- and β-d-glucoside and alkyl β-d-maltoside. The matrix allowed the investigation of the effects of alkyl chain length, headgroup polymerization, and anomeric configuration on the surfactants' physicochemical properties. Increasing the alkyl chain length increases the hydrophobicity and the dispersion interaction between surfactant molecules, as one would expect, resulting in greater thermal stability of thermotropic and lyotropic Phases. Phase transition temperatures are influenced significantly by the anomeric configuration in the shorter octyl derivatives, but to a lesser extent in the longer alkyl chain derivatives. The effect of increasin...
Nobuo Kato - One of the best experts on this subject based on the ideXlab platform.
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photochromism of 1 2 bis 2 methyl 5 phenyl 3 thienyl perfluorocyclopentene in a single Crystalline Phase
Journal of the American Chemical Society, 2000Co-Authors: Masahiro Irie, Thorsten Lifka, And Seiya Kobatake, Nobuo KatoAbstract:1,2-Bis(2-methyl-5-phenyl-3-thienyl)perfluorocyclopentene (1a) and their derivatives, 1,2-bis(2-methyl-5-p-tolyl-3-thienyl)perfluorocyclopentene (2a) and 1,2-bis(2-methyl-5-p-tert-butylphenyl-3-thienyl)perfluorocyclopentene (3a), were found to undergo reversible photochromic reactions in the single-Crystalline Phase. Upon irradiation with 366 nm light the single crystals turned blue. The blue colored crystals returned to colorless by irradiation with visible light (λ > 480 nm). The substituents at para positions of the phenyl groups did not affect the rates of photocyclization reactions both in the single-Crystalline Phase and in hexane. Activation energies of the photocyclization reactions were almost zero. On the other hand, activation energies as much as 5−10 kJ mol-1 were observed in the photocycloreversion reactions in the single-Crystalline Phase. These values were smaller than those observed in solution, ca. 16 kJ mol-1. Slow thermal cycloreversion reaction of the closed-ring isomer (1b) was observ...
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photochromism of 1 2 bis 2 5 dimethyl 3 thienyl perfluoro cyclopentene in a single Crystalline Phase
Journal of the American Chemical Society, 1999Co-Authors: Seiya Kobatake, Nobuo Kato, Taro Yamada, Kingo Uchida, Masahiro IrieAbstract:1,2-Bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene (1a) was found to undergo photochromism in a single Crystalline Phase. Upon irradiation with ultraviolet light the colorless crystal turned red with keeping the crystal shape. The red color is due to the closed-ring form 1b. The red color was bleached by irradiation with visible light (λ > 450 nm). The intensity of the red color observed under polarized light dramatically changed by rotating the crystal sample, and the order parameter was as high as 0.84. The high order parameter confirmed that the molecules undergo photochromism in the Crystalline lattice. The direction of the electronic transition moment of 1b estimated from the absorption anisotropy at 535 nm agreed with the long axis of 1a packed in the crystal, which was determined by X-ray crystallographic analysis. The movement of each atom of the molecule in the crystal during the cyclization reaction was estimated by comparing the structures of 1a and 1b, both of which were determined by X-ray ...
Seiya Kobatake - One of the best experts on this subject based on the ideXlab platform.
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dynamics of cyclization cycloreversion and multiphoton gated reaction of a photochromic diarylethene derivative in Crystalline Phase
Journal of Physical Chemistry C, 2008Co-Authors: Kensuke Tani, Seiya Kobatake, Hiroshi Miyasaka, Yukihide Ishibashi, Masahiro IrieAbstract:Cyclization and cycloreversion reactions of a photochromic diarylethene derivative, bis(2-methyl-5-phenylthiophen-3-yl)perfluorocyclopentene, in Crystalline Phase were investigated by means of picosecond laser spectroscopy. Rapid cyclization within a few picoseconds, as comparable to that in solution Phase, was confirmed for the colorization reaction in the Crystalline Phase. On the other hand, cycloreversion reaction took place with a time constant of 25 ps. In addition, nonlinear enhancement of the cycloreversion process was observed. The excitation intensity dependence of the reaction profiles and the correlation of the apparent reaction yield with the time interval of two pulses employed for the excitation clearly revealed that the successive two-photon absorption process via the S 1 state, leading to higher excited states, opened the efficient cycloreversion process. The dynamics and mechanisms of the multiphoton-gated reaction in the Crystalline Phase were discussed by comparing the present results ...
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photochromism of 1 2 bis 2 ethyl 5 phenyl 3 thienyl perfluorocyclopentene in a single Crystalline Phase conrotatory thermal cycloreversion of the closed ring isomer
Journal of the American Chemical Society, 2000Co-Authors: Seiya Kobatake, Katsunori Shibata, And Kingo Uchida, Masahiro IrieAbstract:1,2-Bis(2-ethyl-5-phenyl-3-thienyl)perfluorocyclopentene (1a) was found to undergo a thermally reversible photochromic reaction in solution as well as in the single-Crystalline Phase. Upon irradiation with ultraviolet light the hexane or toluene solution containing 1a and single-crystal 1a turned blue along with the formation of closed-ring isomer (1b). The blue solution and single crystal returned colorless by irradiation with visible light (λ > 500 nm) or heating above 100 °C. The bleaching is due to the cycloreversion of 1b to 1a. The thermal cycloreversion activation energies were measured in the toluene solution and in the single-Crystalline Phase above 100 °C. The activation energy from photogenerated 1b to 1a in the solution was 128 kJ mol-1, while it decreased to 120 kJ mol-1 in the crystal of the open-ring isomer 1a. In the crystal of the closed-ring isomer 1b the energy increased to 137 kJ mol-1. The cycloreversion reaction was found to be controlled by the environmental conditions. The thermal ...
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photochromism of 1 2 bis 2 methyl 6 nitro 1 benzothiophen 3 yl perfluorocyclopentene in a single Crystalline Phase dichroism of the closed ring form isomer
Journal of the American Chemical Society, 1999Co-Authors: Seiya Kobatake, Taro Yamada, Motoki Yamada, Masahiro IrieAbstract:1,2-Bis(2-methyl-6-nitro-1-benzothiophen-3-yl)perfluorocyclopentene was found to undergo a reversible photochromic reaction in the single-Crystalline Phase. Upon irradiation with 366-nm light, the single crystal turned green with keeping the crystal shape. The colored crystal showed dichroism. When the crystal was rotated under polarized light, the color changed from yellow to blue. The yellow and blue colors were attributed to two perpendicular electronic transitions at 465 and 600 nm of the closed-ring form. The two transition moments coincide with the directions of short and long axes of the closed-ring form isomers, which were regularly packed in the crystal lattice.
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photochromism of 1 2 bis 2 5 dimethyl 3 thienyl perfluoro cyclopentene in a single Crystalline Phase
Journal of the American Chemical Society, 1999Co-Authors: Seiya Kobatake, Nobuo Kato, Taro Yamada, Kingo Uchida, Masahiro IrieAbstract:1,2-Bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene (1a) was found to undergo photochromism in a single Crystalline Phase. Upon irradiation with ultraviolet light the colorless crystal turned red with keeping the crystal shape. The red color is due to the closed-ring form 1b. The red color was bleached by irradiation with visible light (λ > 450 nm). The intensity of the red color observed under polarized light dramatically changed by rotating the crystal sample, and the order parameter was as high as 0.84. The high order parameter confirmed that the molecules undergo photochromism in the Crystalline lattice. The direction of the electronic transition moment of 1b estimated from the absorption anisotropy at 535 nm agreed with the long axis of 1a packed in the crystal, which was determined by X-ray crystallographic analysis. The movement of each atom of the molecule in the crystal during the cyclization reaction was estimated by comparing the structures of 1a and 1b, both of which were determined by X-ray ...