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Crowned spiropyran

FIG. 7.29 Photocontrolled binding of Li by the crowned spiropyran 26 incorporated into a membrane at an electrode surhice. [Pg.249]

Crowned Spiropyrans as Alkali- (Alkaline-Earth) Metal Cation Receptors... [Pg.402]

The crowned spiropyran in the electrically neutral form can bind an alkali metal ion with the crown ether moiety. At the same time, the spirobenzopyran portion isomerizes to the corresponding merocyanine form photo-chemically. The zwitterionic merocyanine form of crowned spirobenzopyran moiety brings about a significant change in the metal-ion binding ability. This prompted the authors to apply the compound to photo-responsive ion-conductive materials. They observed that the ion-conductivity was increased by ultraviolet light and decreased by visible light [259]. [Pg.773]

Fedorova, O.A., Gromov, S.P., Strokach, Yu.P., Pershina, Yu.V., Sergeev, S.A., Barachevsky, V.A., Pepe, G., Samat, A., Guglielmetti, R., Alfimov, M.V. (1999) Crown-containing spironaphthoxazines and spiropyrans. 1. Synthesis and anion- capped complexes of photochromic aza-15-crown-5 ethers with flexible... [Pg.252]

Photoresponsive systems are seen ubiquitously in nature, and light is intimately associated with the subsequent life processes. In these systems, a photoantenna to capture a photon is neatly combined with a functional group to mediate some subsequent events. Important is the fact that these events are frequently linked with photoinduced structural changes in the photoantennae. This suggests that chemical substances that exhibit photoinduced structural changes may serve as potential candidates for the photoantennae. To date, such photochemical reactions as E/Z isomerism of azobenzenes, dimerization of anthracenes, spiropyran-merocyanine interconversion, and others have been exploited in practical photoantennae. It may be expected that if one of these photoantennae were adroitly combined with a crown ether, it would then be possible to control many crown ether family physical and chemical functions by means of an ON/OFF photoswitch. This is the basic concept underlying the designing of photoresponsive crown ethers. We believe that this is one of the earliest examples of molecular machines . [Pg.283]

The ability to tune the photochromic behavior of crown ether-bound spiropyrans, 4a and 5a, by connecting them to metal ions, was investigated by Kimura and his coworkers [10,11]. This complexation of the crown ether moiety with a metal ion accelerates the transformation from spiropy-ran, 4b to merocyanine, 4c, by light or heat. When this complexation effect is weak, thermodynamic equilibrium favors the spiropyran form, and... [Pg.82]

Spironaphthoxazine with a crown ether, 8, also shows photochromic behavior that is sensitive to the type of alkali and alkaline earth metal ions [14]. Other derivatives of spiropyran and spiro oxazine, 9-12, which can chelate metal ions were synthesized, and the effects of complexation on their photochromic behavior have been investigated [15-17]. [Pg.83]

The photochromism of spirobenzopyrans is a well-documented phenomenon that arises from the photoinduced reversible isomerization between spiropyran and merocyanine forms . In spirobenzopyrans carrying a crown ether moiety (e.g., Ill), this interconversion process is affected by metal ion complexation. A strong interaction of the crown ether unit with a metal ion caused the thermal isomerization of the spirobenzopyran residue to the corresponding merocyanine form with simultaneous suppression of the UV-induced isomerization process (negative photochromism) (Scheme 3). Conversely, a weak metal ion interaction induced a positive photochromism <2001JOC1533, 2002EJ0655>. [Pg.701]

The immobilization of photoisomerizable host molecules onto an electrode surface can be used for the construction of novel ion-selective electrodes. A photoisomerizable calix[4]arene derivative was incorporated into a polymeric membrane on an electrode surface and the two different isomeric states of the host molecule provided responses selective to Li" or Na" ions depending on the state.Another photoisomerizable host molecule has been constructed from spiropyran and crown-ether subunits. Different binding affinities for Li were found depending on the isomeric state of the photoisomerizable component (26). The researchers suggested that this effect was caused by the coordination of the Li ion to the 0 of the zwitterionic merocyanine-form (Figure 7.29). The photocontrolled host molecules were immobilized in a polymeric film onto an electrode surface, resulting in a photochemically switchable ion-selective electrode. [Pg.249]

Figure 49 Photocontrol of metal ion binding by aza-crown ether-containing spiropyrans. (Reproduced from Ref. 92. Royal Society of Chemistry, 1991.)... Figure 49 Photocontrol of metal ion binding by aza-crown ether-containing spiropyrans. (Reproduced from Ref. 92. Royal Society of Chemistry, 1991.)...
Extension of this work to other aza-crown ethers and thiacrown ethers containing spiropyrans, spirooxazines, and spirothiopyrans (Figure 50a), based on similar design principles for the binding of different types of metal ions, has subsequently been reported. " " On the other hand, Inouye and coworkers also reported cryptand-containing... [Pg.2013]

Application studies of these crown ether-containing spiropyrans as metal ion transporters in liquid membranes (Figme 51a) have also been examined under various lighting conditions. The transportability of Li+ increases... [Pg.2013]


See other pages where Crowned spiropyran is mentioned: [Pg.334]    [Pg.250]    [Pg.83]    [Pg.1]    [Pg.408]    [Pg.408]    [Pg.409]    [Pg.273]    [Pg.83]    [Pg.334]    [Pg.250]    [Pg.83]    [Pg.1]    [Pg.408]    [Pg.408]    [Pg.409]    [Pg.273]    [Pg.83]    [Pg.431]    [Pg.66]    [Pg.108]    [Pg.114]    [Pg.8]    [Pg.394]    [Pg.403]    [Pg.404]    [Pg.405]    [Pg.410]    [Pg.348]    [Pg.2012]    [Pg.2013]    [Pg.231]    [Pg.1991]    [Pg.1992]    [Pg.1993]   
See also in sourсe #XX -- [ Pg.402 , Pg.403 ]




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