Thienyl fulgides

The same results for the quantum yield of the photoreactions of fulgides 49a-49c have been obtained compared with those of the corresponding furyl fulgide, i.e., bulky substituents of R1 can increase the I e c and decrease the e z and 5 z E. For example, in toluene, f E c =0.73, I C E = 0.095 for 49c.41 Bulky substituents on the alkylidene group (49b) can enhance the C- e by a factor of four compared with the ordinary thienyl fulgide (47). 

It should be pointed out that introduction of electron-donating substituents to the thienyl ring can lead to a red shift of Xmax and an increase of the molar absorption coefficient ( max) of the colored form. However, the quantum yield of bleaching is decreased, e.g., 3 c- e for 50h, 50g, and 48 in toluene were 0.0043 (591), 0.0092 (556), and 0.14 (535), respectively (the values in parenthesis are the irradiation wavelength/nanometer for the bleaching process). 

Effenberger and Wonner63 have described the preparation and photochemistry of an anthrylvinyl thiophen fulgide (51). 

X-ray analysis of 52 and 53 has also been reported by Kaftory.64 The phenyl group is not coplanar with the thiophen ring in any of the compounds 52 and 53. 

The distance between the two carbon atoms that form the new bond in 

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Thienyl fulgide (in PS) can be colored and bleached at all temperatures between 300 and 10 K. The coloring reaction does not require thermal activation, but for the bleaching process a small activation barrier (50 cm 1) exists. Further studies on the photoreaction kinetics of thienyl fulgide derivatives (49a-49c) have been carried out by the same research group,59 as shown in Scheme 14. 

Table 4.12. Spectroscopic Properties of Thienyl Fulgide 49 (E,Z) and its Colored Forms (50)...

H. Konishi, A. Iwasa, S. Kudo, T. Okano, and J. Kiji, Synthesis and properties of long alkyl chain-substituted thienyl fulgides, Chem. Express, 5(7), 481-484 (1990). 

Replacement of the 3-fuiyl group by a 3-thienyl group led to the formation of thienyl-substituted fulgides,58 which have photochromic properties similar to the furyl fulgides. Glaze et al.58 reported that the main difference is a slight bath-ochromic shift of the absorption band of the colored form, 7,7a-dihydrobenzothio-phene (7,7a-DHBT, 48). The photochemical reaction is shown in Scheme 13. 

A. P. Glaze, S. A. Harris, H. G. Heller, W. Johncock, S. N. Oliver, P. J. Strydom, and J. Whittall, Photochromic heterocyclic fulgides. Part 4. The thermal and photochemical reactions of (E)isopro-pylidene [a-2-and-(3-thienyl)ethylidene] succinic anhydrides and related compounds, J. Chem. Soc.,... 

J. Kiji, T. Okano, H. Kitamura, Y. Yokoyama, S. Kubota, and Y. Kurita, Synthesis and photochromic properties of fulgides with a f-butyl substituent on the furyl or thienyl methylidene moiety, Bull. 

Fulgides and Fulgimides - A theoretical study of the photochromic compound 2,3-bis(2,4,5-trimethyl-3-thienyl)maleic anhydride has been reported. The photochromic properties of the indyl fulgide ( )-l-benzyl-2-methyl-3-indylethylindene(isopropylidene) succinic anhydride have been studied.The photochromism of (232) and (233) has been investigated. The cyclizations are reversible and the materials show reasonable fatigue resistance. 

Krayushldn MM, Barachevsky VA, Me M (2007) Synthesis of thienyl-containing photochromes (dithienylethenes, fulgides, fulgimides, and spirocompounds). Heteroatom Chem 18 557-567. doi 10.1002/hc.20334... 

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