Self-Folding Cavitands of Nanoscale Dimensions

Lücking, Ulrich; Tucci, Fábio C.; Rudkevich, and Dmitry M.; Rebek, Julius

doi:10.1021/ja001562l

Cited by 61 publications

(20 citation statements)

References 39 publications

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“…Relative to reported hydrogenbonded clathrate structures, the proportion of included solvent within the crystal structure of 1 is unremarkable; however, its distribution into such large well-defined cavities is unprecedented. Molecular enclosure on the subnanoscale may be achieved within the voids of discrete molecular cages, [21] crystalline clathrates, [4] and network coordination polymers; [22] however, only a few examples approach, [23] and fewer exceed, [24] an enclosed volume of 1 nm 3 . Of interest, is the potential for the exploitation of the functionalities present in the phthalocyanine unit to provide catalytic sites that would be embedded in the wall of the cavities and accessible only through the narrow size-selective channels.…”

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confidence: 99%

A Phthalocyanine Clathrate of Cubic Symmetry Containing Interconnected Solvent‐Filled Voids of Nanometer Dimensions

et al. 2005

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A void apart! A clathrate based on zinc octa(2,6‐diisopropylphenoxy)phthalocyanine contains solvent‐filled voids of exceptionally large volume (>8 nm3; see picture for the packing arrangement). Each nanovoid is enclosed by a cubic assembly of six phthalocyanine molecules and contains 18 molecules of water and an estimated 65 molecules of acetone, which may be exchanged for methanol or water molecules without loss of order.

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confidence: 99%

A Phthalocyanine Clathrate of Cubic Symmetry Containing Interconnected Solvent‐Filled Voids of Nanometer Dimensions

et al. 2005

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“…The addition of the fourth wall and reduction to the diamine gave the common precursor to the monofunctionalized cavitands. These include the self-complementary structure 11, (25) the introverted acid 12 (26), the dipyrrole 13 (27), the porphyrin 14 (28,29), the biscavitand 15 (30), the phenanthroline 16 (20), salen 17 (31), and the pyridone 18 ( Fig. 5) (32).…”

Section: Synthesismentioning

confidence: 99%

Functional cavitands: Chemical reactivity in structured environments

Purse

Rebek

2005

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

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Container-shaped molecules provide structured environments that impart geometric bounds on the motions and conformations of smaller molecular occupants. Moreover, they provide ''solvation'' that is constrained in time and space. When inwardly directed functional groups are present, they can interact chemically with the occupants. Additionally, the potential for reactivity and catalysis is greatly enhanced. Deep cavitands, derived from resorcinarenes, nearly surround smaller molecules and have been one of the most successful platforms for elaboration with functional groups. Derivatives bearing organic and metal-binding functional groups have been shown to affect recognition properties and selectively accelerate diverse reactions. In this review, we examine recent examples of these systems with an emphasis on how and why ordered nanoenvironments impart changes in the properties and reactivity of their occupants.nanoenvironments ͉ supramolecular M olecular recognition became a popular theme in physical organic chemistry during the late 1980s, and many of those studies evaluated intermolecular forces as models for biochemical phenomena. Synthetic receptors of increasing sophistication such as clefts (1), armatures (2), tweezers (3), bowls (4), and other vehicles (5, 6) were devised for the study of reversible interactions, both in aqueous and nonaqueous media. The emergence of site-directed mutagenesis replaced much of this activity. The strength of a hydrogen bond inside, say, an enzyme can be determined in situ through substitution of an unnatural amino acid (7) with the appropriate functional groups. In addition, enzymes, aptamers, ribozymes, and catalytic antibodies can fold more or less completely around a target molecule. This creates a structured environment for the functional group interactions in question, a feature missing in the various concave structures invented by synthetic chemists. A receptor that completely and reversibly encapsulated sizable molecules was prepared in 1995 (8), but it lacked any appropriately positioned functionality. It took us another 5 years to synthesize a receptor that could, more or less, surround a target molecule and present it with a reactive functional group. This led to changes in reactivity of the sort encountered in the macromolecular complexes of biology. We do not intend here to promote these as model systems. Instead, this review is concerned with effects of physical restraints on a molecule surrounded by another; the physical organic chemistry of structured environments. More specifically, the structures are specially modified cavitands, macrocyclic compounds featuring a cavity that is sealed at one end and functionalized at the other. Cavitands have a long history in studies of molecular recognition, and several reviews are available that cover the literature up to 2002 (9-13). With rare exceptions, these cavitands offer only spaces to be filled by smaller molecules. Our departure was their functionalization with groups that are directed at the molecules held tempo...

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“…In compound 61a (Chart 31) two deepened cavities were shown to act independently, by simultaneously complexing two different (adamantyl and cyclohexanyl) guests, one per each cavity [113] On the other hand, the similar compound 61b formed stable 1:1 inclusion complexes with diaryl substituted adamantanes 62a,b [113]. Finally, a porphyrin derivative linker was used to attach two cavitands and to prepare one of the hugest synthetic hosts [114].…”

Section: Bi-cavitands and Clamshell Containersmentioning

confidence: 99%

Resorcarenes: Hollow Building Blocks for the Host-Guest Chemistry

Botta

Cassani

D’Acquarica

et al. 2005

COC

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The continuous search for new qualities and the desirability of controlling the size, shape and the chemical features had led to the successful synthesis of various molecular containers and their complexes starting from resorcarene skeleton. The rigidified cavitands have been extended to capture in their round hug bigger and bigger molecules. By covalent synthesis many kinds of new hosts have been built, that maintain guests in their prison for more and more long time. Self assembly, driven by metal-ligand interaction, van der Waals forces, hydrophobicity and, mainly, hydrogen bonds, is at the base of capsules, a novel type of compounds with a peculiar inner phase, stereochemistry and reactivity. The amazing variety of hollow buildings with a resorcarene-based framework and often unique properties is reviewed. OH HO 1168 Current Organic Chemistry, 2005 Botta et al. RESORCARENES AS CONTAINER 2.1 Resorcarenes and Cations or Charged MoleculesAlso resorcarenes form stable complexes with alkali metal cations (Li I , Na I , K I , Rb I , Cs I ) [14]. The interaction of simple resorcarenes with metal cations and ammonium ions has been extensively studied. The conformational change of the host resorcarene, the most favourable binding locations and the relative binding energies have been investigated by ab initio methods [15]. The same group studied the interaction with cations of resorcarene 3a, (Chart 2) in comparison with its permethylated derivative 3b, by Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (ESI-FT-ICR-MS) and ab initio calculations [16]. The significance of intramolecular hydrogen bonding for the cone conformation and the presence of intramolecular flip-flop hydrogen bonding in 3a were confirmed by calculations and ND 3 -exchange experiments. Regard to the complexation, the following items were established: i) all the above alkali metal cations formed host-guest complexes by docking inside the cavity of the host; ii) the complexation with larger cations, especially Cs + , was favoured; iii) all the cations formed stable dimer resorcarene capsules. Chart 2. Resorcarenes octol (3a) and octamethyl ether (3b).Conversely, Cu II cations were shown to interact with cyano-4a (Chart 3) and amino-resorcarenes 4b, forming in the latter case a complex with octahedrical geometry, as evidenced by the EPR spectrum; accordingly, the computercalculated structure suggested a three-molecular complex between Cu II and two molecules of 4b, in which the ligands use three of their functionalities at the lower rim to fix the ion with a distorted octahedral coordination [17]. Chart 3. Resorcarenes interacting with metal cations.The interaction of resorc[4]arenes octamethyl ethers such as 4c with Fe III in organic media was analysed by 1 H NMR studies, carried out using Ga III instead of Fe III . As a result, resorcarenes bearing carboalkyloxy groups in the side chains were shown to have two active sites of interaction, the first located at the aromatic upper rim and the other in the vicinity ...

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Self-Folding Cavitands of Nanoscale Dimensions

Cited by 61 publications

References 39 publications

A Phthalocyanine Clathrate of Cubic Symmetry Containing Interconnected Solvent‐Filled Voids of Nanometer Dimensions

A Phthalocyanine Clathrate of Cubic Symmetry Containing Interconnected Solvent‐Filled Voids of Nanometer Dimensions

Functional cavitands: Chemical reactivity in structured environments

Resorcarenes: Hollow Building Blocks for the Host-Guest Chemistry

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