The self-assembly of a highly ordered [2]catenane

Ashton, Peter R.; Brown, Christopher L.; Chrystal, Ewan J. T.; Goodnow, Timothy T.; Kaifer, Ángel E.; Parry, Keith P.; Philp, Douglas; Slawin, Alexandra M. Z.; Spencer, Neil; Stoddart, J. Fraser; Williams, David J.

doi:10.1039/c39910000634

Cited by 91 publications

(42 citation statements)

References 10 publications

(14 reference statements)

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“…Apolar binding is generally strongest in solvents with low molecular polarizability and with high cohesive interactions, and it has been suggested that the empirical solvent polarity parameters E T (30) for the various solvents represent a good measure of the interplay between these two factors. [22] That the driving force for the complexation of aromatic guests by the tetracation 9 4 is apolar binding would be also confirmed by a study of solvent effects on the binding equilibria between 9 4 and the guests indole and catechol. [24] The authors reported good linear free-energy relationships between the free energies of complexation and the polarity of the solvent, as measured by Z-values or E T (30) values, indicative of apolar binding complexation.…”

Section: Resultsmentioning

confidence: 81%

Template Effects and Kinetic Selection in the Self-Assembly of Crown Ether Cyclobis(paraquat-p-phenylene) [2]Catenanes—Effect of the 1,4-Dioxybenzene and 1,5-Dioxynaphthalene Units

et al. 2000

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The template effects exerted by bis(p-phenylene)[34]crown-10 (3) and by 1,5-dinaphto[38]crown-10 (4) in the ring-closure reaction of the trication 2(3+) to yield the [2]catenanes 7(4+) and 8(4+) have been quantitatively evaluated in acetonitrile at 62 degrees C by UV/visible spectroscopy. The rate of ring closure of the trication 2(3+) dramatically increases in the presence of the templates 3 and 4, up to approximately 230 times at [3] approximately equals 0.1 molL(-1), and up to approximately 1,900 times at [4] approximately equals 0.01 molL(-1). The outcome of kinetic selection experiments, in which the two crown ethers compete for the incorporation into the catenane structure, has been discussed in the light of the obtained results. It has been shown that the product ratio of catenanes obeys the Curtin-Hammett principle only if the concentrations of the templates are equal and much greater than that of the substrate. Analysis of the rate profiles has shown that the 1,5-dioxynaphthalene unit, present in the template 4, has a greater affinity than the 1,4-dioxybenzene unit, present in the template 3, for the electron-deficient pyridinium rings present in both the transition-state and substrate structures. Ab initio calculations at the 3-21G and 6-31G(d) levels of theory indicate that the greater affinity of the 1,5-dioxynaphthalene unit cannot be explained on the basis of greater pi-pi stacking and [C-H...pi] interactions, but rather on the basis of the model of apolar complexation in which the solvent plays a major role.

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Section: Resultsmentioning

confidence: 81%

Template Effects and Kinetic Selection in the Self-Assembly of Crown Ether Cyclobis(paraquat-p-phenylene) [2]Catenanes—Effect of the 1,4-Dioxybenzene and 1,5-Dioxynaphthalene Units

et al. 2000

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“…1A, the relaxation process must be associated with a free energy of activation (ΔG ‡ value) of less than 16 kcal mol −1 . Both the degenerate (49,50) and nondegenerate (27) [2]catenanes (Fig. 3A), which have been studied in the dim and distant past crystallized (Fig.…”

Section: Resultsmentioning

confidence: 99%

Isolation by crystallization of translational isomers of a bistable donor-acceptor [2]catenane

Wang

Olson

Fang

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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The template-directed synthesis of a bistable donor-acceptor [2]catenane wherein both translational isomers-one in which a tetrathiafulvalene unit in a mechanically interlocked crown ether occupies the cavity of a cyclobis(paraquat-p-phenylene) ring and the other in which a 1,5-dioxynaphthalene unit in the crown ether resides inside the cavity of the tetracationic cyclophane-exist in equilibrium in solution, has led to the isolation and separation by hand picking of single crystals colored red and green, respectively. These two crystalline co-conformations have been characterized separately at both the molecular and supramolecular levels, and also by dynamic NMR spectroscopy in solution where there is compelling evidence that the mechanically interlocked molecules are present as a complex mixture of translational, configurational, and conformational isomers wherein the isomerization is best described as being a highly dynamic and adaptable phenomenon.mechanical bond formation | stereochemistry | template-directed synthesis | structural isomerism | X-ray crystallography T he dynamics and stereochemical behavior of mechanically interlocked molecules (1-3) (MIMs) in solution require a fundamental understanding of the tenets of stereochemistry that reach beyond (4, 5) the commoner garden stereogenic centers that are normally how stereochemistry expresses itself-usually in a kinetically stable fashion-in organic compounds. In the 1980s Schill et al. (6) drew attention to the existence of translational isomerism (7-14) in catenanes and rotaxanes (15, 16). Subsequently, we proposed (17, 18) the use of the term co-conformation to describe different relative spatial arrangements of the components in MIMs-such as bistable [2]catenanes and [2]rotaxanes-in the context of molecular electronic devices (MEDs) (19). The reason we coined this variant of the term conformation is that the translational isomers of catenanes and rotaxanes are frequently (4, 5) separated by free energies of activation in the range of 8-24 kcal mol −1 -that is, the magnitudes of free energy barriers we associate with NMR observable conformational changes and isomerism over the experimentally accessible range of temperatures on commercially available spectrometers.Whereas translational isomerism has some of the structural hallmarks (e.g., observable changes in shape and obvious alterations in structure) of conformational isomerism, and bears some superficial resemblance to it, it is not strictly correct-in the light of generally accepted definitions (20)-to refer to the relative movements between mechanically interlocked components in MIMs as a change in conformation. The reason is that the widely recognized definition (21) of the term conformation is as follows: The conformations of a molecule of defined configuration are the various arrangements of its atoms in space that differ only as after rotation about single bonds. This definition is now commonly extended to include rotation about π-bonds or bonds of partial order between one and two. Translati...

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“…Macrocyclic polyethers incorporating a variety of p-electron-rich aromatic units, such as 1,5-dioxynaphthalene (DNP) [23] and resorcinol [24] ring systems, have also been shown to act successfully as templates for the formation of the tetracationic cyclophane, thus generating [2]catenanes. In addition, introduction of two different p-electron-rich aromatic residues within the same macrocyclic polyether component of a [2]catenane leads to a wide range of molecular structures [25].…”

Section: Catenane Chemistry With the Tetracationic Cyclophanementioning

confidence: 99%

From Cyclophanes to Molecular Machines

Flood

Liu

2004

Modern Cyclophane Chemistry

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A molecular machine [5] is a multicomponent system in which the reversible movement of the components can be controlled by an external stimulus (S). In particular, Fig. 19.1 Structural formula of the tetracationic cyclophane 1 4+ and its graphical representation when a machine is composed of 1) moving parts, and when it is provided with 2) an energy supply, and following 3) a signal to start, can 4) perform work, it is of paramount importance to be able to control the relative locations and motions of the moving parts. It is through the evolving chemistry of the tetracationic cyclophane 1 4+ that the element of control has been established. First, we describe our development of host-guest complexation and the ensuing preparative chemistry leading to pseudorotaxanes, catenanes and rotaxanes. Then, we discuss how we have introduced control (Fig. 19.2) over the motions of components in nondegenerate rotaxanes (Type I), and nondegenerate catenanes (Type II), as well as over the dethreading/rethreading of pseudorotaxanes (Type III). Practically, the movement results in a change in properties which produce a signal that allows the operation of the machine to be monitored. The outside stimuli can be photons, electrons, or chemical species, to generate photochemically-, electrochemically-and chemically-driven molecular machines, respectively. The story that will unfold in this chapter covers two decades of research developments in the design, customization and optimization of molecules interlocked with the tetracationic cyclophane. These developments are a testament to the fact that the tetracationic cyclophane has been, and will continue to be an active key component in building nanoscale molecular machines with controllable movements. 19.2

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The self-assembly of a highly ordered [2]catenane

Cited by 91 publications

References 10 publications

Template Effects and Kinetic Selection in the Self-Assembly of Crown Ether Cyclobis(paraquat-p-phenylene) [2]Catenanes—Effect of the 1,4-Dioxybenzene and 1,5-Dioxynaphthalene Units

Template Effects and Kinetic Selection in the Self-Assembly of Crown Ether Cyclobis(paraquat-p-phenylene) [2]Catenanes—Effect of the 1,4-Dioxybenzene and 1,5-Dioxynaphthalene Units

Isolation by crystallization of translational isomers of a bistable donor-acceptor [2]catenane

From Cyclophanes to Molecular Machines

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