Molecular Recognition of C<sub>60</sub> with γ‐Cyclodextrin

Yoshida, Zen‐ichi; Takekuma, Hideko; Takekuma, Shin‐ichi; Matsubara, Yoshiharu

doi:10.1002/anie.199415971

Cited by 243 publications

(175 citation statements)

References 21 publications

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“…The discovery led to extensive studies on various CD complexes related to tools for nanocomposite [4] and a novel reducing reagent [5]. Geckeler and Constabel reported that cucurbit [7]uril 12 also forms a complex with C 60 by solid-liquid reaction (Figure 3.4) [6]. In these complexes, the attractive interactions between the heteroatoms as an n-donor and the fullerene surface should be operative [7], but the main driving force of the complexes should be hydrophobic effect.…”

Section: Simple Traditional Hostsmentioning

confidence: 99%

Receptors for Pristine Fullerenes Based on Concave–Convex π–πInteractions

Kawase

2012

Supramolecular Chemistry of Fullerenes and Carbon Nanotubes

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In 1990, Kr€ atchmer and coworkers reported the extraction of fullerenes (C 60 and C 70 ) from carbon soot using aromatic solvents (Figure 3.1) [1]. After this discovery, receptor molecules for fullerenes have been extensively studied for separation and purification of fullerenes. Supramlecular chemists have found that traditional host molecules composed of electron-rich aromatic rings such as calix[n]arenes 1-4, oxacalix[3]arenes 5, and cyclotriveratrylenes (CTV) 6 ( Figure 3.2) can be employed for the purpose. The crystallographic analyses of these complexes with C 60 clearly indicated the importance of the p-p interactions between the convex p surface of C 60 and the concave p surface of the traditional host molecules. On the other hand, except a few examples, the traditional hosts bound fullerenes only in solid state. In order to bind with fullerenes more tightly, two strategies have been presented to construct the well preorganized p cavity so far. First, electron-rich aromatic units are introduced to the host molecule as appendants (Figure 3.2a). Second, two host molecules are linked by appropriate tether(s) to form a dimeric structure with a creft-, ring-, or ball-shaped cavity (Figure 3.2b). The binding abilities of the modified receptors fairly increased in comparison with those of simple traditional hosts. On the other hand, new receptors based on curved conjugated systems such as corannulene 7, extended TTF (exTTF) 8, and carbon nanorings (Figure 3.3) have been developed recently. These compounds possess a concave p surface matching to the convex surface of C 60 . Cyclic [6]paraphenyleneacetylene ([6]CPPA) 9 and the related compounds have smooth belt-shaped structure similar to a cut piece of carbon nanotube, and thus may be termed carbon nanorings. These receptors form stable inclusion complexes with fullerenes both in solution and in the solid state, and are good model compounds to explore the nature of the concave-convex p-p interactions. This chapter discusses the fullerene receptors bearing a cavity surrounded by p-orbitals, the so-called p cavity, the concept of molecular designs, and the nature of p-p interactions. The survey of the fullerene receptors should provide an insight into the supramolecular properties of curved conjugated systems. Although the receptor Supramolecular Chemistry of Fullerenes and Carbon Nanotubes, First Edition. Edited by Nazario Martin and Jean-Francois Nierengarten.

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Section: Simple Traditional Hostsmentioning

confidence: 99%

Receptors for Pristine Fullerenes Based on Concave–Convex π–πInteractions

Kawase

2012

Supramolecular Chemistry of Fullerenes and Carbon Nanotubes

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“…Preparation of γ-Cyclodextrin Bicapped C 60 [(γ-CyD) 2 /C 60 ] and C 60 (OH) 24 Solution γ-Cyclodextrin bicapped C 60 [(γ-CyD) 2 /C 60 ] was prepared by the method of Yoshida et al (28,29) with some modification. Briefly, a mixture of C 60 (40.0 mg; 55.6 μmol) and γ-cyclodextrin (120.0 mg; 92.5 μmol) was stirred in a water/toluene (16/6 v/v) mixture at 118 °C for 48 h, and then, γ-cyclodextrin (60.0 mg; 46.3 μmol) was added twice more at 48 h intervals.…”

Section: Chemicalsmentioning

confidence: 99%

“…Then, the solution was filtered/sterilized through a 0.22 μm cellulose acetate membrane to remove the insoluble materials (C 60 released from unstable complexes) and bacteria. The concentration of the solution was determined from its absorbance at 332 nm [log ε = 4.63 (29)]. This solution was prepared fresh before each use because the complex was unstable in water.…”

Section: Chemicalsmentioning

confidence: 99%

Pristine (C₆₀) and Hydroxylated [C₆₀(OH)₂₄] Fullerene Phototoxicity towards HaCaT Keratinocytes: Type I vs Type II Mechanisms

Zhao

Bilski

et al. 2008

Chem. Res. Toxicol.

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The increasing use of fullerene nanomaterials has prompted widespread concern over their biological effects. Herein, we have studied the phototoxicity of γ-cyclodextrin bicapped pristine C 60 [(γ-CyD) 2 /C 60 ] and its water-soluble derivative C 60 (OH) 24 toward human keratinocytes. Our results demonstrated that irradiation of (γ-CyD) 2 /C 60 or C 60 (OH) 24 in D 2 O generated singlet oxygen with quantum yields of 0.76 and 0.08, respectively. Irradiation (>400 nm) of C 60 (OH) 24 generated superoxide as detected by the EPR spin trapping technique; superoxide generation was enhanced by addition of the electron donor nicotinamide adenine dinucleotide (reduced) (NADH). During the irradiation of (γ-CyD) 2 /C 60 , superoxide was generated only in the presence of NADH. Cell viability measurements demonstrated that (γ-CyD) 2 /C 60 was about 60 times more phototoxic to human keratinocytes than C 60 (OH) 24 . UVA irradiation of human keratinocytes in the presence of (γ-CyD) 2 /C 60 resulted in a significant rise in intracellular protein-derived peroxides, suggesting a type II mechanism for phototoxicity. UVA irradiation of human keratinocytes in the presence of C 60 (OH) 24 produced diffuse intracellular fluorescence when the hydrogen peroxide probe Peroxyfluor-1 was present, suggesting a type I mechanism. Our results clearly show that the phototoxicity induced by (γ-CyD) 2 /C 60 is mainly mediated by singlet oxygen with a minor contribution from superoxide, while C 60 (OH) 24 phototoxicity is mainly due to superoxide.

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“…20) Despite numerous studies on the radical scavenging activity of water-soluble fullerenes, little is known about the comparative assay of fullerenes versus -carotene, the latter of which has frequently served as a reference compound in determining antioxidant activity. [21][22][23][24] In the present study, the antioxidant activity of supramolecular water-soluble fullerenes, viz., polyvinylpyrrolidone (PVP)-entrapped C 60 25) and -cyclodextrin (CD)-bicapped C 60 , [26][27][28][29] as shown in Fig. 1, was kinetically evaluated by means of coupled autoxidation of linoleic acid and -carotene.…”

mentioning

confidence: 99%