A kinetic study of guest displacement reactions on a host–guest complex with a photoswitchable calixarene

Letzel, Matthias C.; Schäfer, Christian; Novara, Francesca R.; Speranza, Maurizio; Rozhenko, Alexander; Schoeller, Wolfgang W.; Mattay, Jochen

doi:10.1002/jms.1464

Cited by 14 publications

(11 citation statements)

References 37 publications

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“…21 These systems function well, but less invasive switching processes are also desirable. 22 The two new cavitands presented here respond to light and heat by changing their conformations, but only the tert-butyl substituted 1 forces guests out upon irradiation. The process is reversible and can be cycled numerous times.…”

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confidence: 89%

“…Diederich and co-workers used acid/base chemistry to control the uptake and release of cycloalkanes,20 and we have used metal ions to manipulate a self-included “ouroborand” cavitand 21. These systems function well, but less invasive switching processes are also desirable 22. The two new cavitands presented here respond to light and heat by changing their conformations, but only the tert -butyl substituted 1 forces guests out upon irradiation.…”

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confidence: 99%

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A light controlled cavitand wall regulates guest binding

2011

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Here we report a cavitand with a photochemical switch as one of the container walls. The azoarene switch undergoes photoisomerization when subjected to UV light producing a self-fulfilled cavitand. This process is thermally and photochemically reversible. The reported cavitand binds small molecules and these guests can be ejected from the cavitand through this photochemical process.Molecular devices on the nanoscale continue to attract attention, 1 and a variety of stimuli to drive the machinery are available. Changes in redox, 2 pH, 3 metal ion presence, 4 and other chemical inputs 5 have been used to cycle between well-defined molecular states, but perhaps the oldest-and one of the most frequently used stimuli-is light. In supramolecular devices the trans/cis photoisomerism of the azo benzene module provided the first switching mechanism applied to the binding behavior of cyclodextrins 6 and crown ethers. 7 Its ease of introduction, reliable shape and distance changes and broad applicability, even to foldamers 8 and biological molecules such as proteins comprising ion channels, 9 have insured the popularity of the photoisomerization process. Surprisingly, the azobenzene module has not appeared in deep cavitands and we correct that omission here. 10 In contrast to most photo-switchable devices-where the photo-responsive unit is appended on the structure's periphery to impart function-we integrated it into the cavitand's structure. We devised two light-responsive cavitands that exhibit very different guest binding behavior when exposed to light. Control of guest uptake and release is achieved through an unusual conformational preference, but only when a tert-butyl group is present on the azo-arene substituent. The switching is dictated by weak attractive forces and not through typical covalent bonds or steric constraints.We prepared azo cavitands 1 and 2 in one step from the known mono-amine cavitand 3 11 (Scheme 1). Mixing nitrosoarenes 12 at room temperature in glacial acetic acid with cavitand 3 resulted in the precipitation of pure azo-arene cavitands as orange solids (see ESI † for 1 H, 13 C NMR and mass spectrometry characterization data).In the resting configuration azo-arene cavitands trans-1 and trans-2 present deep cavities for guest binding. Upon irradiation with UV light, the azo substituent undergoes photoisomerization to produce cis-1 and cis-2. The tert-butyl substituent of 1 was expected to fold into and occupy the cavitand void where it can enjoy stabilizing CH-π interactions. In contrast, the unsubstituted azo cavitand cis-2 can neither reach the same CH-π distances nor adequately fill the space.The switching capabilities of 1 and 2 were investigated in d 12 -mesitylene. Both cavitands present only trans configuration by 1 H NMR after heating to reflux and cooling to room temperature in the dark. Under ambient conditions a small percentage of cis cavitand is observed, 8% for 1 and 5% for 2. 13 Computational and crystallographic studies reveal that cis-azobenzene derivatives adopt a n...

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A light controlled cavitand wall regulates guest binding

2011

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“…In previous years many publications on applications of the reversible reaction 1 $ 2 in supramolecular chemistry and materials science appeared. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] In principle, such a switch can be monitored by any (physical) property which is sufficiently different for 1 and 2. An easy control is possible by measuring the absorbance of 1 and 2 at a certain excitation wavelength.…”

Section: Anthracene-x-anthracenementioning

confidence: 99%

“…Mattay et al 11,12,15,16,[21][22][23] synthesized resorcin [4]arenes such as 43 and related compounds, which bear anthracene chromophores on opposite benzene rings. Irradiation at the anthracene absorption at 350 nm transforms 43a-e to the corresponding cycloisomers by intramolecular [4 + 4] cycloadditions; 43f shows a decomposition upon irradiation.…”

Section: Anthracene-anthracene Biplanemersmentioning

confidence: 99%

Optical switches with biplanemers obtained by intramolecular photocycloaddition reactions of tethered arenes

Meier

Cao

2013

Chem. Soc. Rev.

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The dimerization of anthracene by a [4π + 4π] cycloaddition is one of the oldest and best known reactions in photochemistry. In the series of tethered bichromophoric arenes, this reaction type could be extended to anthracene-naphthalene, naphthalene-naphthalene and recently even to anthracene-benzene and naphthalene-benzene systems. Cyclophanes, which can be regarded as twofold or multiple tethered systems, are not discussed here. The cycloisomerizations are performed by irradiation at the long-wavelength absorption (λ > 270 nm), whereas shorter wavelengths (λ < 270 nm) lead to cycloreversions, which can be also achieved by a thermal route. The systems represent therefore a P- and T-type photochromism, which can be used for optical or chiroptical switches. An acceleration of the switch is possible by a singlet energy transfer (light harvesting antenna effect) in dendritic compounds. In the past 5 to 10 years many applications of these switches were studied in the context of photonic devices, sensor techniques, lithographic processes, imaging techniques, data processing and data storage.

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“…But in contrast to the situation in solution, the probability of bimolecular reaction in the gas phase is low. 96,97 Thus, the ESI-MS spectrum is usually a screenshot of the corresponding equilibrium in solution, only to some extent corrected for the thermodynamic stability of species in the gas phase.…”

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