Photoresponsive crown ethers

Figure 6.14. A photoresponsive crown ether capable of performing a photoswitching for modification of cavity size.

Compound 1 is an early example of a photoresponsive crown ether [2,3], 1 has a photofunctional azobenzene cap on an N2O4 crown ring, so that one can... 

Photodimerization of anthracene has frequently been cited as a photochemical switch to create photoresponsive crown ethers. Photoirradiation of 3 in the presence of Li+ gives the photocyclo-isomer 4 [5,6], 4 is fairly stable with Li+ but readily reverts to the open form 3 when Li+ is removed from the ring. In this system, however, intermolecular dimerization may take place competitively... 

For a comprehensive review of photoresponsive crown ethers, please see [11]. 

Shinkai, S. (2001) Switchable molecular receptors and recognition processes from photoresponsive crown ethers to allosteric sugar sensing systems, in Feringa, B.L. (ed.), Molecular Switches, Wiley-VCH, Weinheim, Germany, pp. 281-307. 

Switchable Molecular Receptors and Recognition Processes From Photoresponsive Crown Ethers to Allosteric Sugar Sensing Systems... 

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 . 

S. Shinkai, T. Nakaji, T. Ogawa, K. Shigematsu, O. Manabe, Photoresponsive Crown Ether 2. Photocontrol of Ion Extraction and Ion-Transport by a Bis(Crown Ether) with a Butterfly-Like Motion , J. Am. Chem. Soc., 103, 111 (1981)... 

Photoisomerization of an azobenzene function located in a complex molecule is often accompanied by conformational changes. This approach has again been employed in the construction of photoresponsive crown ethers, a topic which has been the subject of a recent review. Cylindrical ionophores in which two diaza-crown ethers are linked by two photoresponsive azobenzene groups change their ability to bind polymethylene-diammonium salts on irradi-... 

Shinkai, S., Miname, I., Kusano, Y., and Manabe, O. Photoresponsive crown ethers. 5. Light-driven ion transport by crown ethers with a photoresponsive anionic cap. /. Am. Chem. Soc. 1982, 104, 1967-1972. 

New photoresponsive crown ethers incorporating an azobenzene moiety have been prepared. The binding properties of the crown ether (3) containing an intraannular 4-methoxyphenylazo substituent... 

Case Study 6.28 Supramolecular chemistry - photoresponsive crown ethers... 

S. Shinkai, K. Shigematsu, M. Sato and O. Manabe, Photoresponsible crown ethers. Part 6. Ion transport mediated by photoinduced cis-trans interconversion of azobis-(benzocrown ether), J. Chem. Soc., Perkin Trans. I, 1982, 2735-2739 J. Anzai, H. Sasaki, A. Ueno and T. Osa, Photo-induced potential changes across poly(vinyl chloride)-crown ether membranes, J. Chem. Soc., Chem. Commun., 1983, 1045 J. Anzai, H. Sasaki, K. Shimokawa, A. Ueno and T. Osa, Photocontrol of alkali metal ion permeability through the poly(vinyl chloride)/crown ether membranes, Nippon Kagaku Zasshi, 1984, 338. 

The aim of the design of a photoresponsive crown ether is to control the cation binding capacity of the ligand via a photochemical reaction. Expressed in another way, the photoresponsive crown ether exists in two forms a basic (stable) one, and a second one which is obtained by light irradiation... 

Shinkai S, Minami T, Kusano Y, Manabe O. 1983. Photoresponsive crown ethers. 8. Azobenzenophane type switched on crown ethers which exhibit an all or nothing change in ion binding ability. J Am Chem Soc 105(7) 1851 1856. 

Shinkai. S. Shigematsu, K. Kusano, Y. Manabe. O. Photoresponsive crown ethers. Part 3. Photocontrol of ion... 

ABSTRACT. New photoresponsive crown ethers (Iff ") having a crown ring and an ammoniumalkyl (H3N (CH2)n"> n=4,6,10) group attached to the two sides of an azobenzene have been synthesized. Photo-responsive properties (thermal isomerization, metal extraction, membrane transport, etc.) were examined, and the results were compared with those of other photoresponsive crown ethers and complexons. 

Here, we address a new photoresponsive crown ether (IH" ) with an ammonium tail. This... 

As described in Introduction, the basic idea of the photoresponsive crown ethers originates from the responsive action of certain polyether antibiotics. In extensions to membrane transport studies, it was found that these photoinduced changes in affinity could be used to enhance the rate of ion-release from an artificial carrier, thereby increasing the overall rates of either passive or active transport across a membrane. We believe that further elaborations of this concept might lead to the eventual development of a series of photocontrollable membranes. 

Shinkai et al. reported photoresponsive crown ethers (Figure 54) comprising two 15-crown-5 molecules linked by an azobenzene unit, which exhibited a butterfly-like motion. They found that the rate of the thermal isomerization was suppressed by added alkali metal cations and different alkali metal cations could be extracted efficiently by the different conformations of the molecules with high selectivity. These studies demonstrate that in principle ion extraction and ion transport through a liquid membrane can be controlled by light. Although this is not a mechanical molecular machine, it is considered as the prototype of early molecular machines and... 

Other more complex systems have been obtained, consisting by a photoresponsive crown ethers which combines within the same molecule both a crown ether and a photoresponsive chromophore. The polymer changes its conformation in response to irradiation, which in turn induces a change in the complexation ability with suitable alkali metal ions, for instance Cs" [95] ... 

Applications can be envisaged for crown ether systems whose complexing ability is responsive to external stimuli. Prominent amongst these systems are the photoresponsive crown ethers that contain azo-linkages, and one recent example from a series of papers that have appeared over the past few years is the cylindrical ionophore (72) (illustrated as the trans,trans-ionn), whose cavity size, and... 

Shinkai, S. and Manabe, 0. (1984) Photocontrol of Ion extraction and ion transport by photoresponsive crown ethers, Top, Curr. Chem.y 121,67-104. 

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