Kinetic Study of [2]Pseudorotaxane Formation with an Asymmetrical Thread

Quiroga, Miguel; Parajó, M.; Rodríguez‐Dafonte, Pedro; García‐Río, Luis

doi:10.1021/acs.langmuir.6b01348

Cited by 12 publications

(8 citation statements)

References 60 publications

(153 reference statements)

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“…The interest of these compounds in a general context, however, is limited with respect to dibenzylammonium‐type ions because of the much poorer binding with crown ethers and the nontrivial synthetic issues associated with the inclusion of cycloalkane units in the axle components of molecular machines. Conversely, the incorporation of substituted phenyl units in extended axle‐type molecules appears to be a feasible way to implement kinetic barriers or “speed bumps” for ring (de)threading or shuttling …”

Section: Resultsmentioning

confidence: 99%

Precision Molecular Threading/Dethreading

et al. 2020

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The general principles guiding the design of molecular machines based on interlocked structures are well known. Nonetheless, the identification of suitable molecular components for a precise tuning of the energetic parameters that determine the mechanical link is still challenging. Indeed, what are the reasons of the “all‐or‐nothing” effect, which turns a molecular “speed‐bump” into a stopper in pseudorotaxane‐based architectures? Here we investigate the threading and dethreading processes for a representative class of molecular components, based on symmetric dibenzylammonium axles and dibenzo[24]crown‐8 ether, with a joint experimental–computational strategy. From the analysis of quantitative data and an atomistic insight, we derive simple rules correlating the kinetic behaviour with the substitution pattern, and provide rational guidelines for the design of modules to be integrated in molecular switches and motors with sophisticated dynamic features.

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Section: Resultsmentioning

confidence: 99%

Precision Molecular Threading/Dethreading

et al. 2020

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“…The effects on the formation of the inclusion complexes of changing the size of the host cavity [10,[33][34][35][36]39], the hydrophobic chain length of the surfactant [10,37,38], the nature of the surfactant head group [10,39,40], and the number of hydrophobic chains and head groups of the surfactants [10,[41][42][43][44] have been examined. Nonetheless, to the authors´ knowledge, the influence of incorporating a functional group at the end of the hydrophobic surfactant chain on the formation of cyclodextrin-surfactant complexes has not been studied.…”

Section: Discussionmentioning

confidence: 99%

Host-guest interactions between cyclodextrins and surfactants with functional groups at the end of the hydrophobic tail

Martı́n

Ostos

Angulo

et al. 2017

Journal of Colloid and Interface Science

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Graphical abstractIn this work the influence of the incorporation of aromatic substituents at the end of the hydrophobic tail on the binding of cationic surfactants to cyclodextrins was studied. 2 HOST-GUEST INTERACTIONS BETWEEN CYCLODEXTRINS AND SURFACTANTS WITH FUNCTIONAL GROUPS AT THE END AbstractThe aim of this work was to investigate the influence of the incorporation of substituents at the end of the hydrophobic tail on the binding of cationic surfactants to α-, β-, and -cyclodextrins. The equilibrium binding constants of the 1:1 inclusion complexes formed follow the trend K 1 (α-CD)>K 1 (β-CD)>>K 1 (-CD), which can be explained by considering the influence of the CD cavity volume on the host-guest interactions. From the comparison of the K 1 values obtained for dodecyltriethylammonium bromide, DTEAB, to those estimated for the surfactants with the substituents, it was found that the incorporation of a phenoxy group at the end of the hydrocarbon tail does not affect K 1 , and the inclusion of a naphthoxy group has some influence on the association process, slightly diminishing K 1 . This makes evident the importance of the contribution of hydrophobic interactions to the binding, the length of the hydrophobic chain being the key factor determining K 1 . However, the presence of the aromatic rings does influence the location of the host and the guest in the inclusion complexes. The observed NOE interactions between the aromatic protons and the CD protons indicate that the aromatic rings are partially inserted within the host cavity, with the cyclodextrin remaining close to the aromatic rings, which could be partially intercalated in the host cavity. To the authors´ knowledge this is the first study on the association of cyclodextrins with monomeric surfactants incorporating substituents at the end of the hydrophobic tail.

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“…However, the kinetics of the complexation and dissociation processes have only been determined for relatively few complexes, probably less than a hundred. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Of these, most are with the small αCD, fewer with the wider βCD and its derivatives, and rate constants have only been reported for a few complexes with γCD, [23][24][25][26] which has the largest diameter of the natural CDs.…”

Section: Introductionmentioning

confidence: 99%

Complexation Kinetics of Cyclodextrins with Bile Salt Anions: Energy Barriers for the Threading of Ionic Groups

Schönbeck

2019

J. Phys. Chem. B

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Binding constants for thousands of cyclodextrin complexes have been reported in the literature but much less is known about the kinetics of these host-guest complexes. In the present study, inclusion complexes of bile salts with β-cyclodextrin, γ-cyclodextrin and a methylated β-cyclodextrin were studied by NMR lineshape analysis to explore the structural factors that govern the complexation kinetics. For complexes with β-cyclodextrin, the association rate constants ranged from 2×10 6 to 2×10 7 M -1 s -1 while the dissociation rate constants ranged from 12 s -1 to 6000 s -1 at 25 °C. The kinetics were thus significantly slower than for any other β-cyclodextrin complex reported in the literature, due to the large energy barrier for threading the ionic sidechains of the bile salt anions.Bile salts with taurine and glycine sidechains had identical binding affinities but the kinetics differed by a factor of 10. Introduction of a single hydroxyl group at the binding site of the bile salts reduced the lifetimes and binding constants of the complexes more than 50 times. The strong temperature dependence of the rate constants revealed that the large activation energies were mainly enthalpic with a small contribution from entropy. The larger γ-cyclodextrin was threaded by the non-ionic end of the bile salts and the kinetics were too fast to be accurately determined. The study demonstrates that ionic groups on guest molecules constitute significant energy barriers for threading and dethreading of β-cyclodextrin hosts.

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Kinetic Study of [2]Pseudorotaxane Formation with an Asymmetrical Thread

Cited by 12 publications

References 60 publications

Precision Molecular Threading/Dethreading

Precision Molecular Threading/Dethreading

Host-guest interactions between cyclodextrins and surfactants with functional groups at the end of the hydrophobic tail

Complexation Kinetics of Cyclodextrins with Bile Salt Anions: Energy Barriers for the Threading of Ionic Groups

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