Fullerene Monomers Research Articles

Synthesis and Polymerization of Methacrylate Having Fullerene

Two methacrylate monomers containing fullerene on the side chain (AHMA-C60 or AEMA-C60) were synthesized by reacting 4-azidobenzoyloxy-hexyl and -ethyl methacrylate, respectively, with fullerene. 1H and 13C NMR spectra of these monomers revealed each was a mixture of [6,6] bridged azamethanofullerene derivative and azafulleroid derivative resulting from [5,6] additions. The monomers were later copolymerized with t-butyl methacrylate. In the case of anionic copolymerization using a Grignard reagent, the monomers were incorporated in the polymer chain via vinyl chain reactions, resulting in a charm bracelet type fullerene polymer. The copolymer composition was found almost equal to the composition of monomers fed. In radical copolymerizations, low molecular weight oligomers were obtained in low yields, and contained almost equal amounts of the vinyl group to the fullerene monomer incorporated in the polymer, indicating that the fullerene unit played a role of an inhibitor or a degradative chain transfer agent.

Electron Transfer Studies in C78 (C2v‘), C76 (D2), C70 (D5h), and C60 (Ih) Surfactant Aqueous Solutions

C60 (Ih) and several higher fullerenes, namely, C70 (D5h), C76 (D2), and C78 (C2v‘), have been solubilized via capping with suitable surfactants. Excited states and reduced states of these surfactant systems were probed by photolytic and radiolytic techniques. Flash photolytic irradiation at 355 nm of surfactant solutions of C60, C70, C76, and C78 revealed the rapid grow-in of transient (*S1 → *Sn) absorptions with λmax at 920, 660, 650, and 890 nm, respectively. The associated intersystem crossing rates to the energetically lower lying excited triplet states are typically on the order of 9.0 × 108 s-1. Reductive quenching of the excited triplet states by diazabicyclooctane (DABCO) occurs with (0.8−7.4) × 107 M-1 s-1 and yields the fullerene π-radical anions. Direct reduction of surfactant capped fullerene monomers have been studied by means of time-resolved pulse radiolysis with measurements being conducted in the near-IR region. Radiolytic reduction of (C76)surfactant and (C78)surfactant resulted in the...

Capped Fullerenes: Stabilization of Water-Soluble Fullerene Monomers As Studied by Flash Photolysis and Pulse Radiolysis

Functionalization of C60 with hydrophilic groups promotes the water solubility of the fullerene core which leads in aqueous solution to the irreversible formation of clusters. Capping the surface of water-soluble fullerene derivatives with surfactants (cetyltrimethylammonium chloride or Triton X-100) was found to exclude formation of fullerene clusters and, in turn, to stabilize fullerene monomers. Flash photolytic and pulse radiolytic techniques were employed to generated excited and reduced states of fullerene monomers and fullerene clusters 1−3. Fullerene aggregation was found to have no significant effects on the physicochemical properties related to the generation and lifetime of the excited singlet state. Nanosecond studies of the processes following photoexcitation revealed noticeable differences between monomeric and colloidal derivatives 1−3 for the absorption maximum of the corresponding *T1 → *Tn absorptions. Clustering was found to invoke also remarkable changes for the decay of the fullerene's excited triplet state. Similarly, λmax of the π-radical anions 1−3 is very sensitive to the environmental parameters of the accommodating assembly. In surfactant media, the maxima ([(C60•-)(C4H10N+)]surfactant 1010 nm) were generally blue-shifted relative to the analogous γ-CD complexes ([(C60•-)(C4H10N+)]/γ-CD 1030 nm). On the basis of comparison with fullerene clusters and γ-CD-incorporated complexes, evidence was found that suggests the presence of fullerene monomers in a core(fullerene)−shell(surfactant) type structure.

Involvement of C 60 fullerene monomers and aggregates in the photoconductivity of ultrathin bilayer lipid membranes

Abstract Due to its hydrophobic character, the hydrocarbon core of ultrathin phospholipid bilayer membranes lends itself to the insertion of fullerenes. When doped with C 60 these membranes are photoconducting, the photoconductivity being affected by the presence of quenchers of the excited triplet state such as oxygen. The photoconductivity involves trans-membrane electron transfer; its dependence on C 60 concentration and on the excitation wavelength suggests the participation of small aggregates in the membrane. As derived from time-resolved triplet absorption and fluorescence quenching measurements, the suggested mechanism makes more precise (i) the role of the aggregates which might act as a collecting antenna for the benefit of the monomers, and (ii) the role of the monomers which have a much higher yield of photoinduced triplet state formation than the aggregates.