Photochromic perfluorocyclopentenes

Examples for the synthesis of photochromic perfluorocyclopentenes 71 and 72 with the dithienothiophene substituents (Scheme 29) are given in works [77a-c]. 

As for the relevant application, recently, a specific photochromic compound, 1,2-bis(2 -methyl-5 -phenyl-3 -thienyl)perfluorocyclopentene (BP-BTE), and the analogs of HBO, 2,5-bis(5,-0 rt-butyl-benzooxazol-2 -yl)hydroquinone (DHBO), were employed in the high-contrast, reversible, photochromic switching of fluorescence emission and its perfect nondestructive readout (Fig. 14). Due to the large... 

Photochromic dithienyl- and dibenzothienylethenes, particularly those containing the central 1,2-perfluorocyclopentene fragment, belong to the major group of compounds, which have attracted the attention of researchers in the field of information storage (optical memory) and optical switches because their starting (A) and cyclic (B) forms are, in most cases. 

Here typical syntheses of symmetrical products are considered. In Scheme 2, the treatment of bromide 1 with butyllithium under standard conditions in the presence of perfluorocyclopentene affords photochrome 2 (31 %) (99IZV979). Derivatives 3 and 4 were synthesized in a similar way (98KGS927). 

A comparative analysis of the spectroscopic and photochromic properties of dithienylperhydro- and perfluorocyclopentenes were reported in 03EJO1887 and 05JPC9437. Their photochromic properties are similar, but the perhydro derivatives were shown to be thermally and photochemi-cally less stable. 

To realize the above-mentioned systems, we carefully chose suitable switching units and radical moieties. As an initial attempt, we employed l,2-bis(2-methyl-l-benzothiophen-3-yl)perfluorocyclopentene (9a) as a photochromic spin coupler (Scheme 9.2). Compound 9a is one of the most fatigue-resistant diarylethenes [21]. Nitronyl nitroxide was chosen for the spin source, because this radical is jr-conjugative. Thus, we designed molecule 10a, which is an embodiment of the simplified model 8a [37, 62]. 

Scheme 9.2 Photochromism of the switching unit, l,2-bis(2-methyl-l-benzothiophen-3-yl)perfluorocyclopentene (9a) and its biradical derivative 10a.

K. Uchida, T. Ishikawa, M. Takeshita, and M. Irie, Thermally irreversible photochromic systems. Reversible photocyclization of l,2-bis(thiazolyl)perfluorocyclopentenes, Tetrahedron, 54, 6627-6638 (1998). 

X-ray crystallographic study on single-crystalline photochromism of 1,2-bis(2,5-dimethyl-3-thienyl)-perfluorocyclopentene. Bull. Chem. Soc. Jpn., 73, 2179-2184. 

Kobatake, S., Shibata, K., Uchida, K. and Irie, M. (2000) Photochromism of 1,2-bis (2-ethyl-5-phenyl-3-thienyl)-perfluorocyclopentene. Conrotatory thermal cycloreversion of the closed-ring isomer. /. Am. Chem. Soc., 122, 12135-12141. 

Kobatake, S., Yamada, T., LFchida, K., Kato, N., and Irie., M. Photochromism ut 1,2-bis 2,5-diJnethyl-3-thienyl)perfluorocyclopentene in a single crystalline phase. /. Am. 

With the aim of synthesizing new photochromic dihetarylethenes, viz., 5-substituted l,2-bis(thieno[3,2-Z)]thiophen-3-yl)perfluorocyclopentenes 181a-c, 2-(ben-zothiazol-2-yl)-6-bromo-5-methylthieno[3,2-fc]thiophene (182) was subjeeted to metallation. A mixture of lithium derivatives produced by this reaction was treated with octafluorocyclopentene (CsFg) (2000MI1, 2001IZV107). 

The pyridine derivatives, the monodentate l-(2-methyl-5-phenyl-3-thienyl)-2-(2-methyl-5-(4-pyridyl)-3-thienyl)perfluorocyclopentene and the bidentate 1,2-bis (2-methyl-5-(4-pyridyl)-3-thienyl)perfluorocyclopentene, incorporating the DTE moiety as the photochromic unit (4-py-DTEf [50, 51] and 4-py2-DTEf [52]) and the nonfluorinated analog (4-py2-DTE) [53] have been coordinated to various transition metals, allowing the change of physical properties of metal complexes. 

M. M. Krayushkin, M. A. Kahk, D. V. Kozhinov, A. Y. Mart5mkin, Photochromic dihetarylethenes. 22. Synthesis and photochromic properties of unsymmetric alkylthio-substituted l,2-bis-(dithienyl)-perfluorocyclopentenes, Chem. Heterocycl. Compd., 41, 592-597 (2005). 

Bromo-5-chloro-2-methylthiophene (56) was an intermediate for the synthesis of the photochromic diaryl perfluorocyclopentene 57 (Scheme 66) [99, 100], 2-Methyl-thiophene was selectively chlorinated by NCS at C-5, followed by bromi-nation ortho to the tdkyl group. Subsequent selective reaction at the C-Br bond finally gave 57, which in turn could be further modified at the thiophene ring by substitution of chlorine (Scheme 66) [99, 100]. 

Abstract The review considers the synthesis and structures of photochromic products, in which hetaryl substituents are separated by the centtal 1,2-perfluorocyclopentene moiety. It was also briefly presented main methods for synthesis of octafluorocyclopentene and its reactivity. Among methods used for the synthesis of the photochromes, the reactions of hthium derivatives of thiophene, benzothiophene, and other heterocyclic compounds with octafluorocyclopentene, 1,2-dichlorohexafluorocyclopentene, and their analogues are described. Another general method for the synthesis of dihetarylethenes, considered in the review, is based on the McMurry reaction involving the initial... 

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