La2@C72 and Sc2@C72: computational characterizations

The La2@C72 and Sc2@C72 metallofullerenes have been characterized by systematic density functional computations. On the basis of the most stable geometry of 39 C72 hexaanions and the computed energies of the best endofullerene candidates, the experimentally isolated La2@C72 species was assigned the structure coded #10611. The good agreement between the computed and the experimental 13C chemical shifts for La2@C72 further supports the literature assignment (Kato, H.; Taninaka, A.; Sugai, T.; Shinohara, H. J. Am. Chem. Soc. 2003, 125, 7782). The geometry, IR vibrational frequencies, and 13C chemical shifts of Sc2@C72 were predicted to assist its future experimental characterization.     

Crystallographic characterization of isomer 2 of Er2@C82 and comparison with isomer 1 of Er2@C82

The X-ray crystal structure of (Isomer 2 of Er2@C82). NiII(OEP).2(benzene) shows that the fullerene cage in Isomer 2 of Er2@C82 is the C3v isomer (82:8) and that the erbium ions are distributed over 23 interior sites with occupancies ranging from 0.25 to 0.03.     

Structural and Electronic Characteristics of Endohedral Metallofullerenes: Y2C2@C82 and Y2@C84 Isomers

A quantum-chemical study was made of the structure and electronic characteristics of the novel endohedral metallofullerene Y₂C₂@C₈₂ in comparison with the Y₂@C₈₄ isomer. The interactions between the encapsulated Y₂C₂ cluster and the C₈₂ fullerene cage are ionic in nature. The electronic spectrum of Y₂C₂@C₈₂ differs greatly from the "parent" C₈₂ fullerene and has a metal-like form. The results are compared with existing experimental data.     

13C NMR spectroscopic study of scandium dimetallofullerene, Sc2@C84 vs. Sc2C2@C82

Although Sc2C84 has been widely believed to have the form Sc2@C84, the present 13C NMR study reveals that it is a scandium carbide metallofullerene, Sc2C2@C82, which has a C82(C(3v)) cage.     

Sc2@C70 rather than Sc2C2@C68: density functional theory characterization of metallofullerene Sc2C70

Detailed study on Sc(2)C(70) series has been performed based on fully screening for C(70) tetra- and hexa- anions. With a combined methodology of quantum chemistry and statistical mechanics, our calculation results reveal that the Sc(2)C(70), which was proposed as the first metal-carbide endohedral metallofullerene with a non-isolated pentagon rule (non-IPR) cage (Sc(2)C(2)@C(68):6073_C(2v)), is in fact a C(70) non-IPR metallofullerene structure (Sc(2)@C(70):7854_C(2v)) with three pair of pentagon adjacency thanks to its significant thermodynamic and kinetic stability. According to the natural bond analysis and orbital interaction diagram, each scandium atom should only transfer two 4s electrons to the carbon cages and the valence state of Sc(2)@C(70) is (Sc(2+))(2)@C(70) (4-). In addition, the simulation of UV-Vis-NIR spectrum for Sc(2)@C(70):7854_C(2v) shows good accordance to the experimental spectrum.     

TiO2@C Nanostructured Electrodes for the Anodic Removal of Cocaine

The generalization use of therapeutic and illicit drugs are introducing new several chemical pollutants in water. They have been detected in water and sewage samples worldwide, hence they are considered as emerging pollutants. The increase of water threats has a negative impact on the life quality and human health. Among the illicit drugs, cocaine and derivatives are increasingly present, making efficient detection and elimination of wastewater highly prioritaire. In that sense, the main core of this work is the assessment of a novel cost‐efficient electrochemical method based on substrate electro‐oxidation (EO) using low‐cost anodes based on common graphite modified with TiO₂ nanosized particles incorporated on the surface by assisted microwave deposition. Two different diameters (2 and 5 nm) of nanostructured TiO₂@C anodes were tested for cocaine EO reaction using three different electrolytic solutions (NaCl 50 mM, Na₂SO₄ 50 mM or Na₂SO₄ 100 mM). In all cases, the electrochemical oxidation of cocaine appears to be a combination of hypsochromic and hyperchromic processes. Reaching ca. 90 % degradation after 10 minutes for all electrodes, an enhanced efficiency was especially observed for the system with higher cylindrical diameter and NaCl salt medium. The differential pulse (DP) voltammogram, carried out with all assay solutions after 10 minutes of anodic remediation at both electrodes, exhibited an anodic peak consistent with catechol like compounds.     

Crystallographic and Theoretical Investigations of Er2@C2 n (2 n=82, 84, 86): Indication of Distance-Dependent Metal–Metal Bonding Nature

Successful isolation and characterization of a series of Er-based dimetallofullerenes present valuable insights into the realm of metal–metal bonding. These species are crystallographically identified as Er₂@C_s(6)-C₈₂, Er₂@C_3v(8)-C₈₂, Er₂@C₁(12)-C₈₄, and Er₂@C_2v(9)-C₈₆, in which the structure of the C₁(12)-C₈₄ cage is unambiguously characterized for the first time by single-crystal X-ray diffraction. Interestingly, natural bond orbital analysis demonstrates that the two Er atoms in Er₂@C_s(6)-C₈₂, Er₂@C_3v(8)-C₈₂, and Er₂@C_2v(9)-C₈₆ form a two-electron-two-center Er−Er bond. However, for Er₂@C₁(12)-C₈₄, with the longest Er⋅⋅⋅Er distance, a one-electron-two-center Er−Er bond may exist. Thus, the difference in the Er⋅⋅⋅Er separation indicates distinct metal bonding natures, suggesting a distance-dependent bonding behavior for the internal dimetallic cluster. Additionally, electrochemical studies suggest that Er₂@C_82–86 are good electron donors instead of electron acceptors. Hence, this finding initiates a connection between metal–metal bonding chemistry and fullerene chemistry.     

Separation of N2@C60 and N@C60

We describe the HPLC separation and identification of N@C60 and N2@C60. These species were observed after eleven sequential HPLC separations. Their retention times are in the same range as those of the other noninteractive endohedral species of C60, such as noble gas endohedral C60. The separation factors of these endohedrals were evaluated by using a mixture of hexane/toluene as eluent. We note that this is the first evidence for the N2@C60 molecule existing in the form of endohedral C60 complex.     

Structure of a missing-caged metallofullerene: La2@C72

The La2@C72 metallofullerene having the so-called "missing" C72 fullerene cage was structurally elucidated by using 13C NMR and 139La NMR spectroscopy. The obtained structure of La2@C72 does not satisfy fullerene's structural golden rule, that is, the isolated-pentagon rule. The structure is consistent with a non-IPR D2-C72 (#10611) cage structure where each La atom is situated close to one of the two-fused pentagons.     

Electronic and Spectroscopic Properties of La2@C112 Isomers

Among the 3352 isolated pentagon rule(IPR) isomers and 129073 non-IPR isomers satisfying adjacent pentagon pairs(APPs) ≤ 2 of fullerene C₁₁₂, the lowest-energy IPR and non-IPR isomers of C₁₁₂ and C₁₁₂^6- have been fully screened by the density functional tight-binding(DFTB) and density functional theory(DFT) methods for stu-dying the electronic and spectroscopic properties of La₂@C₁₁₂. The structural features and infrared and absorption spectra of those isomers were analyzed in detail, and the characteristic fingerprint absorption peaks were assigned. To clarify the relative stabilities of La₂@C₁₁₂ isomers at high temperature, entropy contributions were determined at the B3LYP level. IPR isomer La₂@C₁₁₂(C₂:860136) is not the lowest-energy isomer but is one of the most important isomers. This is the first work that considers non-IPR C₁₁₂ isomers when exploring the structure and properties of La₂@C₁₁₂.     

Do Carbon Nano-onions Behave as Nanoscopic Faraday Cages? A Comparison of the Reactivity of C60, C240, C60@C240, Li+@C60, Li+@C240, and Li+@C60@C240

From the analysis of the polarizability of carbon nano-onions (CNOs), it was concluded that CNOs behave as near perfect nanoscopic Faraday cages. If CNOs behave as ideal Faraday cages, the reactivity of the C₂₄₀ cage should be the same in Li⁺@C₂₄₀ and Li⁺@C₆₀@C₂₄₀. In this work, the Diels–Alder reaction of cyclopentadiene to the free C₂₄₀ cage and the C₆₀@C₂₄₀ CNO together with their Li⁺-doped counterparts were analyzed using DFT. It was found that in all cases the preferred cycloaddition is on bond [6,6] of type B of C₂₄₀. Encapsulation of Li⁺ results in lower enthalpy barriers due to the decrease of the energy of the LUMO orbital of the C₂₄₀ cage. When the Li⁺ is placed inside the CNO C₆₀@C₂₄₀, the decrease in enthalpy barrier is similar to that of Li⁺@C₂₄₀. However, the location of Li⁺ in Li⁺@C₂₄₀ (off-centered) and Li⁺@C₆₀@C₂₄₀ (centered) is quite different. When Li⁺ was placed in the center of the C₂₄₀ cage in Li⁺@C₂₄₀, the barriers increased significantly. Taking into account this effect, the barriers in Li⁺@C₂₄₀ and Li⁺@C₆₀@C₂₄₀ differ by about 4 kcal mol⁻¹. This result can be attributed to the shielding effect of C₆₀ in Li⁺@C₆₀@C₂₄₀. As a result, we conclude that this CNO does not act as a perfect Faraday cage.