Endohedral metallofullerenes (EMFs) have novel structures and properties that are closely associated with the internal metallic species. Benzyl radical additions have been previously shown to form closed-shell adducts by attaching an odd number of addends to open-shell EMFs (such as Sc₃C₂@I_h-C₈₀) whereas an even number of groups are added to closed-shell EMFs (for example Sc₃N@I_h-C₈₀). Herein we report that benzyl radical addition to the closed-shell La₂@I_h-C₈₀ forms a stable, open-shell monoadduct instead of the anticipated closed-shell bisadduct. Single-crystal X-ray diffraction results show the formation of a stable radical species. In this species, the La−La distance is comparable to the theoretical value of a La−La covalent bond and is shorter than reported values for other La₂@I_h-C₈₀ derivatives, providing unambiguous evidence for the formation of direct La−La bond.

Although the major isomers of M@C₈₂ (namely M@C_2v(9)-C₈₂, where M is a trivalent rare-earth metal) have been intensively investigated, the lability of the minor isomers has meant that they have been little studied. Herein, the first isolation and crystallographic characterization of the minor Y@C₈₂ isomer, unambiguously assigned as Y@C_s(6)-C₈₂ by cocrystallization with Ni(octaethylporphyrin), is reported. Unexpectedly, a regioselective dimerization is observed in the crystalline state of Y@C_s(6)-C₈₂. In sharp contrast, no dimerization occurs for the major isomer Y@C_2v(9)-C₈₂ under the same conditions, indicating a cage-symmetry-induced dimerization process. Further experimental and theoretical results disclose that the regioselective dimer formation is a consequence of the localization of high spin density on a special cage-carbon atom of Y@C_s(6)-C₈₂ which is caused by the steady displacement of the Y atom inside the C_s(6)-C₈₂ cage.

Endohedral metallofullerenes (EMFs) have novel structures and properties that are closely associated with the internal metallic species. Benzyl radical additions have been previously shown to form closed-shell adducts by attaching an odd number of addends to open-shell EMFs (such as Sc₃C₂@I_h-C₈₀) whereas an even number of groups are added to closed-shell EMFs (for example Sc₃N@I_h-C₈₀). Herein we report that benzyl radical addition to the closed-shell La₂@I_h-C₈₀ forms a stable, open-shell monoadduct instead of the anticipated closed-shell bisadduct. Single-crystal X-ray diffraction results show the formation of a stable radical species. In this species, the La−La distance is comparable to the theoretical value of a La−La covalent bond and is shorter than reported values for other La₂@I_h-C₈₀ derivatives, providing unambiguous evidence for the formation of direct La−La bond.

Although the major isomers of M@C₈₂ (namely M@C_2v(9)-C₈₂, where M is a trivalent rare-earth metal) have been intensively investigated, the lability of the minor isomers has meant that they have been little studied. Herein, the first isolation and crystallographic characterization of the minor Y@C₈₂ isomer, unambiguously assigned as Y@C_s(6)-C₈₂ by cocrystallization with Ni(octaethylporphyrin), is reported. Unexpectedly, a regioselective dimerization is observed in the crystalline state of Y@C_s(6)-C₈₂. In sharp contrast, no dimerization occurs for the major isomer Y@C_2v(9)-C₈₂ under the same conditions, indicating a cage-symmetry-induced dimerization process. Further experimental and theoretical results disclose that the regioselective dimer formation is a consequence of the localization of high spin density on a special cage-carbon atom of Y@C_s(6)-C₈₂ which is caused by the steady displacement of the Y atom inside the C_s(6)-C₈₂ cage.

Fullerenes are of tremendous interest from fundamental researches to applied perspectives in the past decades. However, their application in supercapacitors has been underdeveloped for a long time. Here, the KOH activation of C₇₀ microtubes is reported at high temperatures, which provides activated samples exhibiting excellent capacitive properties. The improved capacitive performance can be attributed to three aspects: the generation of macropores and micropores, the introduction of oxygen functionalities, and the formation of graphitic carbons from ellipsoidal fullerenes. The optimum activated state for supercapacitor application is achieved at 600 °C, at which the product exhibits the best electrochemical behavior with a gravimetric capacitance of 362.0 F g⁻¹ at 0.1 A g⁻¹ and excellent cycling stability with capacitance retention of 92.5% over 5000 cycles at 1 A g⁻¹.

We have made a systematic investigation of the regioselective reaction between triethylamine and C₆₀ under thermal conditions, presenting X-ray crystallographic results of the pentane-fused adduct for the first time. In addition to finding the reaction conditions which gave the highest yield and the best regioselectivity, we captured with GC–MS the acetaldehyde and diethylamine intermediates that were involved in the reaction, thus clarifying the reaction mechanism.

Embedding endohdedral metallofullerenes (EMFs) into electron donor–acceptor systems is still a challenging task owing to their limited quantities and their still largely unexplored chemical properties. In this study, we have performed a 1,3-dipolar cycloaddition reaction of a corrole-based precursor with Sc₃N@C₈₀ to regioselectively form a [5,6]-adduct (1). The successful attachment of the corrole moiety was confirmed by mass spectrometry. In the electronic ground state, absorption spectra suggest sizeable electronic communications between the electron acceptor and the electron donor. Moreover, the addition pattern occurring at a [5,6]-bond junction is firmly proven by NMR spectroscopy and electrochemical investigations performed with 1. In the electronically excited state, which is probed in photophysical assays with 1, a fast electron-transfer yields the radical ion pair state consisting of the one-electron-reduced Sc₃N@C₈₀ and of the one-electron-oxidized corrole upon its exclusive photoexcitation. As such, our results shed new light on the practical work utilizing EMFs as building blocks in photovoltaics.

The chemical properties of carbide-cluster metallofullerenes (CCMFs) remain largely unexplored, although several new members of CCMFs have been discovered recently. Herein, we report the reaction between Sc₂C₂@C_3v(8)-C₈₂, which is viewed as a prototypical CCMF because of its high abundance, and 3-triphenylmethyl-5-oxazolidinone (1) to afford the corresponding pyrrolidino derivative Sc₂C₂@C_3v(8)-C₈₂(CH₂)₂NTrt (2; Trt=triphenylmethyl). Single-crystal X-ray crystallography studies of 2 revealed that the reaction takes place at a [6,6]-bond junction, which is directly over the encapsulated C₂ unit and is far from either of the two scandium atoms. On the basis of theoretical calculations and by considering previously reports, we have found that a hexagonal carbon ring on the cage of Sc₂C₂@C_3v(8)-C₈₂ is highly reactive toward different reagents due to the overlap of high p-orbital axis vector (POAV) angles and large LUMO coefficients. We propose that this highly concentrated area of reactivity is generated by the encapsulation of the Sc₂C₂ cluster because this region is absent from the empty fullerene C_3v(8)-C₈₂. Moreover, the absorption and electrochemical results confirm that derivative 2 is more stable than pristine Sc₂C₂@C_3v(8)-C₈₂, thus illuminating its potential applications.

Fullerene derivatives with different addition patterns exhibit different physical, chemical, and biological properties, which are important for fullerene applications. Novel and rare 1,2,3,16-functionalized [60]fullerene derivatives having a five-membered heterocycle fused to a [5,6]-junction were obtained with high regioselectivity by electrochemical derivatization of a [60]fulleroindoline. The product structures were determined by spectroscopic data and single-crystal X-ray analysis. The obtained high regioselectivity was rationalized using theoretical calculations.

Fullerene derivatives with different addition patterns exhibit different physical, chemical, and biological properties, which are important for fullerene applications. Novel and rare 1,2,3,16-functionalized [60]fullerene derivatives having a five-membered heterocycle fused to a [5,6]-junction were obtained with high regioselectivity by electrochemical derivatization of a [60]fulleroindoline. The product structures were determined by spectroscopic data and single-crystal X-ray analysis. The obtained high regioselectivity was rationalized using theoretical calculations.

Although all the pure-carbon fullerene isomers above C₆₀ reported to date comply with the isolated pentagon rule (IPR), non-IPR structures, which are expected to have different properties from those of IPR species, are obtainable either by exohedral modification or by endohedral atom doping. This report describes the isolation and characterization of a new endohedral metallofullerene (EMF), La₂@C₇₆, which has a non-IPR fullerene cage. The X-ray crystallographic result for the La₂@C₇₆/[Ni^II(OEP)] (OEP=octaethylporphyrin) cocrystal unambiguously elucidated the C_s(17 490)-C₇₆ cage structure, which contains two adjacent pentagon pairs. Surprisingly, multiple metal sites were distinguished from the X-ray data, which implies dynamic behavior for the two La³⁺ cations inside the cage. This dynamic behavior was also corroborated by variable-temperature ¹³⁹ La NMR spectroscopy. This phenomenon conflicts with the widely accepted idea that the metal cations in non-IPR EMFs invariably coordinate strongly with the negatively charged fused-pentagon carbons, thereby providing new insights into modern coordination chemistry. Furthermore, our electrochemical and computational studies reveal that La₂@C_s(17 490)-C₇₆ has a larger HOMO–LUMO gap than other dilanthanum-EMFs with IPR cage structures, such as La₂@D_3h(5)-C₇₈ and La₂@I_h(7)-C₈₀, which implies that IPR is no longer a strict rule for EMFs.