Isolation and structure determination of missing fullerenes Gd@C74(CF3) n through in situ trifluoromethylation

Nd─Nd Bond in Ih and D5h Cage Isomers of Nd2 @C80 Stabilized by Electrophilic CF3 Addition

Synthesis of molecular compounds with metal-metal bonds between 4f elements is recognized as one of the fascinating milestones in lanthanide metallochemistry. The main focus of such studies is on heavy lanthanides due to the interest in their magnetism, while bonding between light lanthanides remains unexplored. In this work, the Nd─Nd bonding in Nd-dimetallofullerenes as a case study of metal-metal bonding between early lanthanides is demonstrated. Combined experimental and computational study proves that pristine Nd2 @C80 has an open shell structure with a single electron occupying the Nd─Nd bonding orbital. Nd2 @C80 is stabilized by a one-electron reduction and further by the electrophilic CF3 addition to [Nd2 @C80 ]- . Single-crystal X-ray diffraction reveals the formation of two Nd2 @C80 (CF3 ) isomers with D5h -C80 and Ih -C80 carbon cages, both featuring a single-electron Nd─Nd bond with the length of 3.78-3.79 Å. The mutual influence of the exohedral CF3 group and endohedral metal dimer in determining the molecular structure of the adducts is analyzed. Unlike Tb or Dy analogs, which are strong single-molecule magnets with high blocking temperature of magnetization, the slow relaxation of magnetization in Nd2 @Ih -C80 (CF3 ) is detectable via out-of-phase magnetic susceptibility only below 3 K and in the presence of magnetic field.

Dietary zero-dimensional fullerene supplementation improves the meat quality, lipid metabolism, muscle fiber characteristics, and antioxidative status in finishing pigs

With the increasing demand for high-quality pork, more nutritional substances have been studied for the regulation of meat quality. Zero-dimensional fullerenes (C60) can modulate the biological behavior of a variety of cell lines and animals. In this study, we report the biological effects of C60 on finishing pigs at different concentrations. A total of 24 barrows (Duroc × Large White × Landrace), with an average body weight of 21.01 ± 0.98 kg, were divided into 3 groups and each treated daily with C60 (100 or 200 mg per kg feed) or a control diet until the end of the experiment. Our results showed that dietary C60 supplementation improved flesh color, marbling scores, and flavor amino acid contents of longissimus dorsi (LD) of growing-finishing pigs (P < 0.05). C60 improved meat quality by regulating lipid metabolism and muscle fiber morphology by mediating the expression of genes, L-lactic dehydrogenase (LDH), myosin heavy chain (MyHC) IIa, MyHCIIb, peroxisome proliferator-activated receptor γ (PPARγ), and fatty acid transport protein 1 (FATP1) (P < 0.05). Moreover, C60 substantially promoted the mRNA expression of antioxidant enzyme genes (P < 0.05), which also contributed to improving meat quality. These findings have important implications for the application of C60 in the livestock industry, especially for improving the meat quality of fattening pigs.

Electrophilic Trifluoromethylation of Dimetallofullerene Anions en Route to Air-Stable Single-Molecule Magnets with High Blocking Temperature of Magnetization

Lanthanide dimetallofullerenes with single-electron M-M bonds are an important class of single molecular magnets and qubit candidates, but stabilization of their unique electronic and spin structure in the form of a neutral molecule requires functionalization of the fullerene cage with a single radical group. The lack of selectivity of the currently available procedure results in a complicated and tedious separation process. Here we demonstrate that electrophilic trifluoromethylation of a mixture of metallofullerene anions with Umemoto reagent II is highly selective toward M₂@C₈₀^- (M = Tb, Y) anions, yielding M₂@C₈₀(CF₃) monoadducts as the main reaction product. Single-crystal X-ray diffraction study proved attachment of the CF₃ group to the pentagon/hexagon/hexagon junction and revealed that positions of metal atoms inside the fullerene cage in the cocrystal with NiOEP are strongly related to the position of the porphyrin moieties. Magnetic characterization of Tb₂@C₈₀(CF₃) showed that it is a robust single-molecule magnet with broad magnetic hysteresis, 100 s blocking temperature of 25 K, and the relaxation barrier of 801(4) K, corresponding to the flipping of the Tb magnetic moment in the strongly ferromagnetically coupled [Tb³⁺-e-Tb³⁺] spin system.

Capturing unconventional metallofullerene M@C60 through activation of the unreactive [5,6] bond toward Diels-Alder reaction

Full control of the regioselectivity in the functionalization of fullerenes is important for production of fullerene derivatives with desirable properties. Cycloaddition reactions of C60 usually take place at the hexagon-hexagon ring junction, i.e. the [6,6] bond of the fullerene cage, whereas the [5,6] bond is generally unreactive. The activation of the [5,6] bond toward Diels-Alder reactions is difficult because of its longer bond length than the [6,6] bond. In this study, we computationally demonstrate that the [5,6] bond of C60 can be efficiently activated by encapsulation of a divalent metal atom such as Ca or Sm. Electron transfer from the metal atom to the fullerene cage and the interaction between the metal cation and the cage play critical roles in enhancing the reactivity of the [5,6] bond. The physical origin of the reactivity enchancement of the [5,6] bond is investigated quantitatively by using the activation strain model and the energy decomposition method. The change in the orbital interaction energy along the intrinsic reaction coordinate has a major effect on the thermodynamics and kinetics of the reactions between Ca@C60 and cyclopentadiene. Both mono- and bis-addition reactions of cyclopentadiene with Ca@C60 prefer to take place at the [5,6] bonds of the fullerene cage thermodynamically, which is distinct from the case of pristine C60. The HOMO-LUMO energy gap of Ca@C60 is remarkably enlarged upon mono- and bis-functionalization with cyclopentadienes. Therefore, the covalent derivatization strategy can be used to capture the unconventional, missing metallofullerene M@C60.

Determining addition pathways and stable isomers for CF3 functionalization of endohedral Gd@C60

Using density functional theory approaches, we follow the sequential addition of CF3 functional groups to the surface of the metallic endofullerene species Gd@C60. The presence of gadolinium in the interior of the cage strongly influences the addition sequence. The calculations are able to successfully identify end points in the addition sequence at Gd@C60(CF3) n , n = 3 and two isomers at n = 5, in predictive agreement with experiment. Inverting the algorithm to determine the most labile groups also identifies the correct positively charged Gd@ C 60 ( C F 3 ) 4 + isomer, as confirmed by experimental mass spectra. The importance of surface mobility, notably at later stage addition, is discussed.