Dithienylethene photoswitch

The water-soluble assemblies, which were encapsulated in lanthanide nanoparticles by an amphiphilic polymer shell containing photochromic dithienylethenes, were prepared. Fluorescence emission in the visible region was observed, when the assemblies were excited with NIR at 980 nm. The emission could be controlled by the photoswitch of the dithienylethenes. Photoswitchable nanoparticles constructed with the Ir complex (110) as a fluorophore and the dithienylethene (111) were developed. The fluorescence photoswitching of the... 

In the search for reversible photoswitchable systems, dithienylethenes seem promising, as the change in geometry during the photochromic reaction IS small and can prevent disorientation. A PMNIA film doped with OFl (I0"o w Av) was poled at 120°C under a corona discharge (6 kV) and sub-nutted to a sequence of alternate irradiations in the visible (514 nm) and in the U V (325 nm) (see Figure 10.9). ... 

Interest in photochromic systems other than those based on the hexa-fluorocyclopentene moiety continues to grow. The photochemical reactivity of the two photoswitches (35) is similar, and irradiation is efficient with conversions of 85% and quantum yields of around 0.6. The novel photo-chromic systems (36) undergo reversible ring closure in a reaction analogous to that observed in the bisthienyl system. Qin et al. have studied the novel pyridyl substituted cyclopentene system (37). This undergoes photocyclization with an enhanced quantum yield when the reactions are carried out in the presence of a metal. The pyridine units are capable of co-ordinating with the metal. The photochromic dithienylethene unit tethered to 3-cyclodextrin (38) has been used as a photoswitch to control the uptake of porphyrin. A series of new photochromic molecules (39) have been synthesized and studied. These exhibit the usual cyclization on irradiation. " The terthiophene derivatives (40) exhibit reversible photochemical cyclization (at 313 nm) and reversion (at wavelengths >460 nm) reactions. The cycles can be carried out many times... 

The influence on the photochromism in dithienylethene systems of replacing the favoured perfluorocylopentene moiety by other cyclic ethene units has attracted the attention of a number of research groups. Dutch workers have shown that the use of the perhydrocyclopentene unit as in (91) has little effect on the photochromic behaviour of (92) but note that in situations where fatigue resistance and thermal stability are critical, the fluorinated moiety would be preferable. The cyclization quantum yield of (93) is reported to increase in the presence of metal ions, and more detailed accounts have been published of the interesting application of the dithienylcyclopentene-tethered jS-cyclodextrins (94) as photoswitchable hosts for meso tetrakis(4-sulfonatophenyl)porphyrin. ... 

ICE. Maly, M.D. Wand, R.P. Lemieux, Bistable ferroelectric liquid crystal photoswitch triggered by a dithienylethene dopant. J. Am. Chem. Soc. 124, 7898-7899 (2002)... 

Two sets of chiral-nematic hybrid are chemically bonded to the same dithienylethene core as for the photoswitchable nematic GLC (30), resulting in a smectic C -cholesteric GLC as depicted in Fig. 6.10. A sample of (31) was placed between two alignment-coated fused silica substrates for heating to 230 °C followed by cooling to 207 °C, where shearing was applied to induce alignment. The... 

Fig. 3 Light controlled association of TPPS by bis-CD bridged with photoswitchable dithienylethene-tether and short linker. Reprinted with permission from ref. 31. Copyright 2004 John Wiley and Sons.

The conducting properties of a photoswitching dithienylethene on Au were investigated using DFT calculation. A device which was... 

Dithienylethene and derivatives. l,2-Di(2,5-dimethylthien-3-yl)cyclopentene and its derivatives are generally termed dithienylethenes or diarylethenes. Their photochromic properties with the reversible cyclization/cycloreversion are fascinating for chemist and material scientists and have been widely applied to photoswitch, optical memory, etc. in molecular devices and in nanotechnology. Therefore, many researchers are seeking possibilities to move the frontiers. In the last two years many novel dithienylethenes have been prepared and their photochromie properties were investigated. 

The axially chiral dithienylethenes (83) and (84) acted as thermally stable photoswitches for nematic liquid ciystals. There are three conformers of the diaiylethene (85) bearing chiral functional groups. 

Dithienylethene-combined metal complexes as redox-active moieties are fascinating as photoswitchable valence systems. Many metal... 

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