Resorcinarenes with 2-benzimidazolone bridges: Self-aggregation, self-assembled dimeric capsules, and guest encapsulation

Ebbing, Maurits H. K.; Villa, M. J.; Valpuesta, José M.; Prados, Pilar; Mendoza, Javier de

doi:10.1073/pnas.072652599

Cited by 116 publications

(59 citation statements)

References 17 publications

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“…The entry and exit of the guests occurs through movement here, and this region attracts polar groups of encapsulated molecules. [30,31] A molecule appears frozen in time and in space while inside a capsule, typically for one to two seconds. Its interactions with other encapsulated molecules are extended and, compared to the random and rapid collisions and exchange of partners that occur in bulk solution, are intensified or amplified in the capsule.…”

Section: Forces Within Capsulesmentioning

confidence: 99%

Simultaneous Encapsulation: Molecules Held at Close Range

2005

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Reversible encapsulation creates spaces where molecules are temporarily isolated from others in solution. Molecules are held within the space of the capsule for lifetimes ranging from milliseconds to hours, and conventional NMR spectroscopy can be used to report on the chemical and magnetic environment as well as the arrangement of the molecules in the encapsulation complex. The complexes self-assemble when, and only when, the spaces inside the capsules are appropriately filled. The weak intermolecular forces that hold these self-assemblies together allow equilibration of the encapsulation complexes at ambient temperatures and pressures in the liquid phase. When two or more molecules are simultaneously encapsulated, intermolecular phenomena are revealed in solution that cannot be observed by other methods. We describe here the unique behavior that emerges from molecules that are simultaneously encapsulated and includes new forms of stereochemistry, isomerism, and asymmetry inside capsules.

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Section: Forces Within Capsulesmentioning

confidence: 99%

Simultaneous Encapsulation: Molecules Held at Close Range

2005

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“…In summary, the capsule acts as a compartment, in which a reagent is sequestered but can be displaced by the reaction products into the solution. Further examples have demonstrated that a combination of two different guests may fit in a capsule better than either guest alone [158,166]. The non-linear kinetics of this compartmentalization reaction was studied in depth in a separate paper [163].…”

Section: Rebek's Capsulesmentioning

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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“…Rather than simple concerted rotation about the N−C Ar bond observed in amide derived cavitands, a more complex process must be invoked for cavitands 2a−d, involving cis-trans isomery of the ureido groups. 7 The small temperature coefficients observed, especially for H3, suggest the formation of a cooperative cyclic array of hydrogen bonds along the rim. This is corroborated by a molecular model of 2 computed at the DFT level of theory (see the Supporting Information).…”

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confidence: 94%