Autoencapsulation Through Intermolecular Forces: A Synthetic Self-Assembling Spherical Complex

Meißner, Robert; Rebek, Julius; Mendoza, Javier de

doi:10.1126/science.270.5241.1485

Cited by 234 publications

(105 citation statements)

References 17 publications

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“…USA 96 (1999)dissociation rate of 1⅐P⅐1 can be obtained from heterodimerization experiments using two different softballs. To a solution of 1⅐P⅐1 was added another softball (lacking phenolic hydroxyl groups) (17). The appearance of the new heterodimer containing P requires the dissociation of 1⅐P⅐1 and takes place over the course of days.…”

Section: Resultsmentioning

confidence: 99%

Guest exchange in an encapsulation complex: A supramolecular substitution reaction

Santamarı́a

Martı́n

Hilmersson

et al. 1999

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

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Encapsulation complexes are reversibly formed assemblies in which small molecule guests are completely surrounded by large molecule hosts. The assemblies are held together by weak intermolecular forces and are dynamic: they form and dissipate on time scales ranging from milliseconds to days-long enough for many interactions, even reactions, to take place within them. Little information is available on the exchange process, how guests get in and out of these complexes. Here we report that these events can be slow enough for conventional kinetic studies, and reactive intermediates can be detected. Guest exchange has much in common with familiar chemical substitution reactions, but differs in some respects: no covalent bonds are made or broken, the substrate is an assembly rather than a single molecule, and at least four molecules are involved in multiple rate-determining steps.Molecule-within-molecule complexes can be regarded as a phase of matter wherein guest molecules are kept inside host structures held together by strong covalent bonds. The earliest systems were prepared a decade ago by Cram and co-workers (1) and Collet and co-workers (2) and were kinetically stable. In these systems-carceplexes and cryptophanes-the hosts can stabilize reactive intermediates (3), produce new forms of stereoisomerism (4), and distinguish between guests and their mirror images (5). Encapsulation complexes are related recently synthesized structures in which hosts are held together by weaker forces, such as hydrogen bonds (6) and metal-ligand interactions (7,8). The systems self-assemble reversibly from subunits and are dynamic (9). They can feature large cavities in which more than one guest can be accommodated (10), behave as nanometric chambers for bimolecular reactions, and offer promise in catalysis (11). We have now examined one such system, the conceptual ''softball'' (12) and address here a fundamental step of assembly and encapsulation-how guests enter and depart. MATERIALS AND METHODSThe solvent p-xylene-d 10 was obtained from Cambridge Isotope Laboratories and was used as received for all guest exchange experiments. All the guests employed for the study were obtained from Aldrich. Adamantane (A) and ferrocene (F) were further purified by sublimation under reduced pressure. Standard solutions of the capsule 1⅐1 (2 mM) and the guests (10-50 mM) were prepared for the kinetic experiments. The guest exchange was monitored by 1 H NMR (600 MHz) with the probe maintained at constant temperature. For the study represented in Fig. 4 each data point was obtained under pseudo-first-order kinetic conditions. The components for all of the samples were mixed at 293 K, and data acquisition was automatically performed at 289 K every 3.5 min. For the experiment represented in Fig. 3 the data points were taken every 5 min. RESULTS AND DISCUSSIONThe softball consists of two self-complementary subunits held together by a seam of 16 hydrogen bonds in a roughly spherical assembly (Fig. 1). In solvents such as p-xylene-d 10 the NMR ...

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Section: Resultsmentioning

confidence: 99%

Guest exchange in an encapsulation complex: A supramolecular substitution reaction

Santamarı́a

Martı́n

Hilmersson

et al. 1999

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

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“…Upon binding of a guest, for example, adamantane or ferrocene, in 20-20, two molecules of solvent that are present in the cavity are released, resulting in a favorable increase in entropy. NMR studies also revealed that the softball was capable of encapsulating two aromatic solvent molecules, 82,83 and this propensity stimulated the researchers to utilize the "softball" as a microreactor for bimolecular reactions. An example is depicted in Figure 3a, viz., the Diels-Alder reaction between p-benzoquinone 21 and cyclohexadiene 22.…”

Section: Noncovalent Systemsmentioning

confidence: 99%

Self‐Assembled Nanoreactors

et al. 2005

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“…Many investigations have been devoted to the study, the design, and the synthesis of new molecular containers. Thus, different guest molecules have been trapped in a large variety, in size and shape, of host cages [15][16][17][18][19]. Molecular container compounds have been used for different purposes such as: to inhibit very reactive species, to isolate molecules from their surrounding, as a chamber for micro-reactions, to store atoms, ions, or small molecules such as H 2 and CH 4 .…”

Section: Introductionmentioning

confidence: 99%

Molecular hydrogen encapsulation in spherophanes

Saal

Jarrosson

Ouamerali

et al. 2009

Chemical Physics Letters

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Molecular hydrogen insertion in and release from four molecular containers, spherophanes, have been studied with different computational methods. It has been found that dispersion interactions are very important in these systems; they govern their stability and the potential energy barriers. The calculated energy barriers are very high so that H 2 could not enter to/release from the cavity of the spherophanes through the benzene rings. The hydrogen molecule would rather prefer to follow the 4H-approach. The M05-2X/6-31G(d) results show that the encapsulation of H 2 inside these spherophanes is stabilizing. The energy barriers for H 2 to enter to (to release from) the spherophanes' cages are compared with those of open fullerenes.

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Autoencapsulation Through Intermolecular Forces: A Synthetic Self-Assembling Spherical Complex

Cited by 234 publications

References 17 publications

Guest exchange in an encapsulation complex: A supramolecular substitution reaction

Guest exchange in an encapsulation complex: A supramolecular substitution reaction

Self‐Assembled Nanoreactors

Molecular hydrogen encapsulation in spherophanes

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