Photochromism of a Novel 6π Conjugate System Having a Bis(2,3′‐benzothienyl) Unit.

Yamaguchi, Tadatsugu; Fujita, Yuji; Irie, Masahiro

doi:10.1002/chin.200436095

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“…Among various types of photochromic compounds, the diarylethenes bearing thiopheneor benzothiophene-derived are the most promising candidates for the applications because of their excellent fatigue resistant [5] and outstanding thermally irreversible photochromic performance [6]. Although agreat number of publications concerning this class of diarylethenes have been reported so far [1,[7][8][9], most of them are symmetrical and amorphous diarylethenes, reports on asymmetrical and crystalline derivatives are very rare [10][11][12]. In the perfluorocyclopentene ring, distances C11-C12, C12-C13, C13-C14, C14-C15 and C11-C15 are 1.505 Å, 1.511 Å,1.525Å , 1.499 Å and 1.377 Å,respectively.…”

Section: Discussionmentioning

confidence: 99%

Crystal structure of 3,3,4,4,5,5-hexafluoro-{[1-(2-ethyl-3-benzothienyl)-2- (2-n-heptyl-5-formyl)]-thien-3-yl}-cyclopent-1-ene, C27H26F6OS2

Li¹,

Pu²,

Fan³

et al. 2008

Zeitschrift Für Kristallographie - New Crystal Structures

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C 27 H 26 F 6 OS 2 ,monoclinic, P12 1 /c1(no. 14), a =13.504(2) Å, b =20.624(3) Å, c =9.781(2) Å, b =103.513(2)°, V =2648.7 Å 3 , Z =4,R gt (F) =0.063, wR ref (F 2 ) =0.220, T =291 K. Source of materialFirst, 4-bromo-2-n-heptyl-5-(1,3-dioxolane)thiophene 1 was prepared according to the procedure [1]. Then, 2-ethylbenzothiophene 2 was obtained by reacting benzothiophene (5.00 g, 37.26 mmol) with ethylbromide (3.05 ml, 40.98 mmol) in the presence of n-BuLi(15.60 ml)/THF solution at 195 K. 3-bromo-2-ethylbenzothiophene 3 was obtained by brominating compound 2 (5.70 g, 37.26 mmol) with N-bromosullirimide (6.88 g, 38.64 mmol). Lithiation of compound 3 (6.79 g, 26.63 mmol) followed by the addition of excess octafluorocyclopentene (3.64 mL, 0.136 mL/mol) simultaneously generated 3-bromo-2-ethyl-3-benzothienyl-perflourocyclopentene 4 (4.22 g, 11.92 mmol), which could be further treated with the anion generated from compound 1 (3.96 g, 11.92 mmol) to yield 1-(2-ethyl-3-benzothienyl)-2-{2-n-heptyl-5-[2-(1,3-dioxolane)]-3-thienyl} perfluorocyclopenten 5 (2.81 g, 4.77 mmol). Finally, the title compound was produced in 81.3% yield by hydrolyzing compound 5 and the colorless crystals were obtained by slow vapor diffusion of chloroform. DiscussionPhotochromic diarylethenes undergo reversible photoisomerization between two isomers with different absorption spectra upon irradiation with light of appropriate wavelength [2]. The two isomers differ from one another not only in the absorption spectra but also in various physical and chemical properties, and the instant property changes by photoirradiation without processing lead to their use in various optoelectronic devices, such as optical memory [3] and optical switches [4]. Among various types of photochromic compounds, the diarylethenes bearing thiopheneor benzothiophene-derived are the most promising candidates for the applications because of their excellent fatigue resistant [5] and outstanding thermally irreversible photochromic performance [6]. Although agreat number of publications concerning this class of diarylethenes have been reported so far [1, 7-9], most of them are symmetrical and amorphous diarylethenes, reports on asymmetrical and crystalline derivatives are very rare [10][11][12]. In the perfluorocyclopentene ring, distances C11-C12, C12-C13, C13-C14, C14-C15 and C11-C15 are 1.505 Å, 1.511 Å,1.525Å , 1.499 Å and 1.377 Å,respectively. These data indicate clearly that the C11-C15 bond is adouble bond, being significantly shorter than the other C-C single bonds. The distance between the reactive carbon atoms C8 and C19 is 3.904 Å. This distance is short enough for the photoreaction to take place in the crystalline phase [13]. The title molecule has four planer rings, including two thiophene rings, one benzene ring and one perfluorocyclopentene ring. So, there are three dihedral angles between every two adjacent rings. The dihedral angles between the perfluorocyclopentene ring and the two thiophene rings are 66.2°for S1/C1/C6/C7/C8 and 60.9°for S2/C19/C16/C17...

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Section: Discussionmentioning

confidence: 99%

Crystal structure of 3,3,4,4,5,5-hexafluoro-{[1-(2-ethyl-3-benzothienyl)-2- (2-n-heptyl-5-formyl)]-thien-3-yl}-cyclopent-1-ene, C27H26F6OS2

Li¹,

Pu²,

Fan³

et al. 2008

Zeitschrift Für Kristallographie - New Crystal Structures

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Photochromism of a Novel 6π Conjugate System Having a Bis(2,3′‐benzothienyl) Unit.

Abstract: Unit. -A novel photochromic system having a bis(2,3'-benzothienyl) unit is synthesized. The derivatives (V) and (VIII) undergo a thermally irreversible photochromic reaction upon alternate irradiation with UV and visible light. -(YAMAGUCHI*, T.; FUJITA, Y.; IRIE, M.; Chem.

Cited by 1 publication

References 1 publication

Crystal structure of 3,3,4,4,5,5-hexafluoro-{[1-(2-ethyl-3-benzothienyl)-2- (2-n-heptyl-5-formyl)]-thien-3-yl}-cyclopent-1-ene, C27H26F6OS2

Crystal structure of 3,3,4,4,5,5-hexafluoro-{[1-(2-ethyl-3-benzothienyl)-2- (2-n-heptyl-5-formyl)]-thien-3-yl}-cyclopent-1-ene, C27H26F6OS2

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