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Artificial Molecular Machines.

Erbas-Cakmak S, Leigh DA, McTernan CT, Nussbaumer AL - Chem. Rev. (2015)

View Article: PubMed Central - PubMed

Affiliation: School of Chemistry, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.

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bonded molecules and on catenanes and rotaxanes in which switching of other protic solvents... This effect (listed in descending binding ability) stations on the thread, macrocycle In these systems, fast-responding reporters are preferred... practical applications by utilizing molecular scale changes to create macroscopic effects... The thread of these rotaxanes included an anthracene fluorophore similar application in synthetic polymers often furnishes a useful result... of Brownian motion can be exploited to great effect in the synthesis every aspect of functional molecule and materials design... An improved robotics” in which ratcheted motions of molecular components

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(a) Molecular structure of the photoswitchable piperidine base 133, and (b) X-ray structure of the photoswitchable piperidinebase 133. X-ray crystal structure reprinted with permissionfrom ref (1418). Copyright2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
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fig53: (a) Molecular structure of the photoswitchable piperidine base 133, and (b) X-ray structure of the photoswitchable piperidinebase 133. X-ray crystal structure reprinted with permissionfrom ref (1418). Copyright2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mentions: Severalexamples of photoswitchable catalytic systems have been reported.1407,1413−1415 The reactivity of the catalytic unit istypically controlled through alteration of the steric shielding ofthe active site or by bringing the catalytic units into closer proximity.In these examples, switching between the cis and trans forms of a photochromic group such as an azobenzeneor a stilbene, or the electrocyclization of a diarylethene, providesthe requisite control. An early example of a photoswitchable catalystwas published by Rebek Jr. and co-workers.1416 Two adenine receptors capable of forming complexes with purine baseswere linked through a trans azobenzene moiety. Whenthe system was isomerized to its cis conformation,the rate of reaction between an amine and p-nitrophenylester was markedly increased due to greater proximity between thereactive groups, which increased the effective molarity of these groupsand thus increased the rate of reaction. A switchable catalyst basedon a light-responsive cavitand was published by the same group. Thecavitand was functionalized with an azobenzene switch and the cavityof the trans state accessible to a guest molecule,while the cis conformation could not bind guests.Piperidinium acetate was used as the guest, and it could be shownthat the host–guest complex significantly accelerated a Knoevenagelcondensation between malononitrile and an aromatic aldehyde.1417 Hecht and co-workers described the photoswitchabletertiary piperidine derivative 133, which could functionas a general base catalyst in a Henry reaction between p-nitrobenzaldehyde and nitroethane (Figure 53). Catalysis was regulated through the shielding/deshieldingof the catalytic site upon irradiation of an azobenzene unit.1418 The reversible shielding and deshielding ofa catalytic site by photoisomerization has also been used to controlthe organocatalytic activity of a thiourea and a guanidine catalyst.1419,1420


Artificial Molecular Machines.

Erbas-Cakmak S, Leigh DA, McTernan CT, Nussbaumer AL - Chem. Rev. (2015)

(a) Molecular structure of the photoswitchable piperidine base 133, and (b) X-ray structure of the photoswitchable piperidinebase 133. X-ray crystal structure reprinted with permissionfrom ref (1418). Copyright2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4585175&req=5

fig53: (a) Molecular structure of the photoswitchable piperidine base 133, and (b) X-ray structure of the photoswitchable piperidinebase 133. X-ray crystal structure reprinted with permissionfrom ref (1418). Copyright2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Mentions: Severalexamples of photoswitchable catalytic systems have been reported.1407,1413−1415 The reactivity of the catalytic unit istypically controlled through alteration of the steric shielding ofthe active site or by bringing the catalytic units into closer proximity.In these examples, switching between the cis and trans forms of a photochromic group such as an azobenzeneor a stilbene, or the electrocyclization of a diarylethene, providesthe requisite control. An early example of a photoswitchable catalystwas published by Rebek Jr. and co-workers.1416 Two adenine receptors capable of forming complexes with purine baseswere linked through a trans azobenzene moiety. Whenthe system was isomerized to its cis conformation,the rate of reaction between an amine and p-nitrophenylester was markedly increased due to greater proximity between thereactive groups, which increased the effective molarity of these groupsand thus increased the rate of reaction. A switchable catalyst basedon a light-responsive cavitand was published by the same group. Thecavitand was functionalized with an azobenzene switch and the cavityof the trans state accessible to a guest molecule,while the cis conformation could not bind guests.Piperidinium acetate was used as the guest, and it could be shownthat the host–guest complex significantly accelerated a Knoevenagelcondensation between malononitrile and an aromatic aldehyde.1417 Hecht and co-workers described the photoswitchabletertiary piperidine derivative 133, which could functionas a general base catalyst in a Henry reaction between p-nitrobenzaldehyde and nitroethane (Figure 53). Catalysis was regulated through the shielding/deshieldingof the catalytic site upon irradiation of an azobenzene unit.1418 The reversible shielding and deshielding ofa catalytic site by photoisomerization has also been used to controlthe organocatalytic activity of a thiourea and a guanidine catalyst.1419,1420

View Article: PubMed Central - PubMed

Affiliation: School of Chemistry, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

bonded molecules and on catenanes and rotaxanes in which switching of other protic solvents... This effect (listed in descending binding ability) stations on the thread, macrocycle In these systems, fast-responding reporters are preferred... practical applications by utilizing molecular scale changes to create macroscopic effects... The thread of these rotaxanes included an anthracene fluorophore similar application in synthetic polymers often furnishes a useful result... of Brownian motion can be exploited to great effect in the synthesis every aspect of functional molecule and materials design... An improved robotics” in which ratcheted motions of molecular components

No MeSH data available.