Bilateral π-extension of an open-[60]fullerene in a helical manner

The conventional π-elongation of open-[60]fullerenes could only give unilaterally π-extended derivatives. Herein, we report the further π-elongation at another site to achieve bilateral π-elongation via a consecutive nucleophilic addition of 4, 5-dimethyl-o-phenylenediamine. The thus-formed π-extended open-[60]fullerene bears two-fold diaza[n]helicene (n = 5 and 6) motifs in its skeleton. The crystallographic analysis revealed the characteristic helicene–fullerene interactions with close contacts of 3.09 and 3.14 Å

Open-[60]fullerene–aniline conjugates with near-infrared absorption

Two open-[60]fullerene–aniline conjugates were synthesized, in which the two-fold addition of diamine gave a thiazolidine-2-thione ring on the [60]fullerene cage in the presence of CS₂. By increasing the number of N, N-dimethylaniline moieties, the absorption edge was considerably shifted up to 1200 nm owing to effective acceptor–donor interactions

Application of Solid-State and High-Pressure Reactions for Fullerene Derivatization and CO2 Activation (ORGANIC MATERIALS CHEMISTRY-High-Pressure Organic Chemistry)

Under the solid-state reaction conditions, a nucleophilic addition of organozinc reagent occurs on fullerene C60 to give a monoadduct together with a bisadduct and a cyclopropanofullerene. Surprisingly, the fullerene C60 also undergoes a clean [2+2] type dimerization by the action of KCN or Mg powder under the similar reaction conditions. The fullerene dimer thus obtained is the very first example of (C60)2, and its structure has been determined by the X-ray crystallography. The use of high pressure (5000 atm) was also shown to be advantageous for a liquid-phase [4+2] cycloaddition of C60. The high-pressure reaction of CO with supercritical CO2 has been found to effect the C-C bond formation affording an oxalate salt in good yield in the presence of Cs2CO3

EPR study of NO radicals encased in modified open C60 fullerenes

Using pulsed electron paramagnetic resonance (EPR) techniques, the low-temperature magnetic properties of the NO radical being confined in two different modified open C60-derived cages are determined. It is found that the smallest principal g value g3, being assigned to the axis of the radical, deviates strongly from the free electron value. This behaviour results from partial compensation of the spin and orbital contributions to the g3 value. The measured g3 values in the range of 0.7 yield information about the deviation of the locking potential for the encaged NO from axial symmetry. The estimated 17 meV asymmetry is quite small compared to the situation found for the same radical in polycrystalline or amorphous matrices ranging from 300 to 500 meV. The analysis of the temperature dependence of spin relaxation times resulted in an activation temperature of about 3 K, assigned to temperature-activated motion of the NO within the modified open C60-derived cages with coupled rotational and translational degrees of freedom in a complicated three-dimensional locking potential

Amphiphilic γ-cyclodextrin–fullerene complexes with photodynamic activity

Amphiphilic γ-cyclodextrin–fullerene 2 : 1 complexes (CLFCH complexes) were prepared by high-speed vibration milling of lipophilic tail-grafted γ-cyclodextrin (γ-CD), hydrophilic tail-grafted γ-CD and fullerene C₆₀. The transamidation of γ-CD–fullerene complexes having two amino groups with lipophilic and hydrophilic activated esters also afforded amphiphilic CLFCH complexes. Self-assemblies consisting of amphiphilic CLFCH complexes efficiently generated singlet oxygen under photoirradiation. Under visible light irradiation conditions, CLFCH complexes bearing a vitamin E moiety as a lipophilic tail showed high photodynamic activity toward cancer cells

Nuclear magnetic resonance of hydrogen molecules trapped inside C70 fullerene cages

We present a solid-state NMR study of H2 molecules confined inside the cavity of C70 fullerene cages over a wide range of temperatures (300?K to 4?K). The proton NMR spectra are consistent with a model in which the dipole–dipole coupling between the ortho-H2 protons is averaged over the rotational/translational states of the confined quantum rotor, with an additional chemical shift anisotropy ?HCSA=10.1?ppm induced by the carbon cage. The magnitude of the chemical shift anisotropy is consistent with DFT estimates of the chemical shielding tensor field within the cage. The experimental NMR data indicate that the ground state of endohedral ortho-H2 in C70 is doubly degenerate and polarized transverse to the principal axis of the cage. The NMR spectra indicate significant magnetic alignment of the C70 long axes along the magnetic field, at temperatures below ~10?

Symmetry-breaking in the endofullerene H2O@C60 revealed in the quantum dynamics of ortho and para-water: a neutron scattering investigation

Inelastic neutron scattering (INS) has been employed to investigate the quantum dynamics of water molecules permanently entrapped inside the cages of C60 fullerene molecules. This study of the supramolecular complex, H2O@C60, provides the unique opportunity to study isolated water molecules in a highly symmetric environment. Free from strong interactions, the water molecule has a high degree of rotational freedom enabling its nuclear spin isomers, ortho-H2O and para-H2O to be separately identified and studied. The INS technique mediates transitions between the ortho and para spin isomers and using three INS spectrometers, the rotational levels of H2O have been investigated, correlating well with the known levels in gaseous water. The slow process of nuclear spin conversion between ortho-H2O and para-H2O is revealed in the time dependence of the INS peak intensities over periods of many hours. Of particular interest to this study is the observed splitting of the ground state of ortho-H2O, raising the three-fold degeneracy into two states with degeneracy 2 and 1 respectively. This is attributed to a symmetry-breaking interaction of the water environment

Surgery of fullerenes

Recent attempts at the synthesis of endohedral fullerenes by organic reactions, so-called molecular surgery methods, are surveyed. The creation of an opening on the surface of fullerene cages allowed insertion of He, H2, H2O, or CO within the cages. An effective route to suture an opening was established to realize a new endohedral fullerene, H2@C60. Further development of this operation as well as the properties and reactions of H2@C60 are summarized. Also the application of the encapsulated H2 molecule as an NMR probe for the study of aromaticity of ionic fullerenes is described