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Azafullerenes derived from nitrogen substitution of carbon cage atoms render direct modifications of the cage skeleton, electronic, and physicochemical properties of fullerene. Gas-phase ionized monometallic endohedral azafullerene (MEAF) [La@C

Hundreds of members have been synthesized and versatile applications have been promised for endofullerenes (EFs) in the past 30 y. However, the formation mechanism of EFs is still a long-standing puzzle to chemists, especially the mechanism of embedding clusters into charged carbon cages. Here, based on synthesis and structures of two representative vanadium–scandium–carbido/carbide EFs, VSc 2 C@ I h (7)-C 80 and VSc 2 C 2 @ I h (7)-C 80 , a reasonable mechanism—C 1 implantation (a carbon atom is implanted into carbon cage)—is proposed to interpret the evolution from VSc 2 C carbido to VSc 2 C 2 carbide cluster. Supported by theoretical calculations together with crystallographic characterization, the single electron on vanadium (V) in VSc 2 C@ I h (7)-C 80 is proved to facilitate the C 1 implantation. While the V=C double bond is identified for VSc 2 C@ I h (7)-C 80 , after C 1 implantation the distance between V and C atoms in VSc 2 C 2 @ I h (7)-C 80 falls into the range of single bond lengths as previously shown in typical V-based organometallic complexes. This work exemplifies in situ self-driven implantation of an outer carbon atom into a charged carbon cage, which is different from previous heterogeneous implantation of nonmetal atoms (Group-V or -VIII atoms) driven by high-energy ion bombardment or high-pressure offline, and the proposed C 1 implantation mechanism represents a heretofore unknown metal–carbon cluster encapsulation mechanism and can be the fundamental basis for EF family genesis.

The reaction of μ3-CCF Dy2TiC@Ih-C80 with AdN2 affords only one [6,6]-open monoadduct along with the addition sites adjacent to the Ti4+ ion instead of the two Dy3+ ions, revealing the decisive role of the non-rare earth metal Ti(IV).

Monometallic cyanide clusterfullerenes (CYCFs) represent a unique branch of endohedral clusterfullerenes with merely one metal atom encapsulated, offering a model system for elucidating structure-property correlation, while up to now only C82 and C76 cages have been isolated for the pristine CYCFs. C84 is one of the most abundant fullerenes and has 24 isomers obeying the isolated pentagon rule (IPR), among which 14 isomers have been already isolated, whereas the C2v(17)-C84 isomer has lower relative energy than several isolated isomers but never been found for empty and endohedral fullerenes. Herein, four novel C84-based pristine CYCFs with variable encapsulated metals and isomeric cages, including MCN@C2(13)-C84 (M = Y, Dy, Tb) and DyCN@C2v(17)-C84, have been synthesized and isolated, fulfilling the first identification of the missing C2v(17)-C84 isomer, which can be interconverted from the C2(13)-C84 isomer through two steps of Stone-Wales transformation. The molecular structures of these four C84-based CYCFs are determined unambiguously by single-crystal X-ray diffraction. Surprisingly, although the ionic radii of Y3+, Dy3+, and Tb3+ differ slightly by only 0.01 A, such a subtle difference leads to an obvious change in the metal-cage interactions, as inferred from the distance between the metal atom and the nearest hexagon center of the C2(13)-C84 cage. On the other hand, upon altering the isomeric cage from DyCN@C2(13)-C84 to DyCN@C2v(17)-C84, the Dy-cage distance changes as well, indicating the interplay between the encapsulated DyCN cluster and the outer cage. Therefore, we demonstrate that the metal-cage interactions within CYCFs can be steered via both internal and external routes.

Endohedral clusterfullerenes featuring the encapsulation of metal clusters within carbon cages exhibit intriguing physical and chemical properties inaccessible to empty fullerenes. Thus far, their syntheses are predominantly fulfilled by using gaseous sources, suffering from low yield, and requiring an additional gas inlet and a heating pretreatment up to 1000 °C. Herein, we employ an ancient pigment, Prussian blue (Fe4[Fe(CN)6]3), as a cheap solid cyanide/nitrogen dual-source, affording the simplified yet high-yield simultaneous syntheses of novel dysprosium (Dy)-based metal cyanide clusterfullerenes (CYCFs) DyCN@C2n and metal nitride clusterfullerenes Dy3N@C2n. Surprisingly, the (CN)− anion of Fe4[Fe(CN)6]3 survives under the extremely high temperature (up to 4000 K) of plasma generated via DC-arc discharge, and functions as the cyanide source of CYCFs. Under the optimized Dy : [CN] : C molar ratio of 1 : 1 : 15, the sum yield of isolated DyCN@C2n (2n = 76, 82) CYCFs produced using Fe4[Fe(CN)6]3 is about 2.8 times higher than that obtained using gaseous N2 source. Moreover, the molecular structures of the three isomers of DyCN@C82 are unambiguously determined by single-crystal X-ray diffraction, indicating that the encapsulated triangular DyCN cluster is tunable due to strong metal–cage interactions. This study paves the way for the low-cost and high-yield syntheses of pricey endohedral fullerenes.

Trimetallic carbide clusterfullerenes (TCCFs) encapsulating a quinary M3C2 cluster represent a special family of endohedral fullerenes with an open-shell electronic configuration. Herein, a novel TCCF based on a medium-sized rare earth metal, dysprosium (Dy), is synthesized for the first time. The molecular structure of Dy3C2@Ih(7)-C80 determined by single crystal X-ray diffraction shows that the encapsulated Dy3C2 cluster adopts a bat ray configuration, in which the acetylide unit C2 is elevated above the Dy3 plane by ∼1.66 Å, while Dy–Dy distances are ∼3.4 Å. DFT computational analysis of the electronic structure reveals that the endohedral cluster has an unusual formal charge distribution of (Dy3)8+(C2)2−@C806− and features an unprecedented three-center single-electron Dy–Dy–Dy bond, which has never been reported for lanthanide compounds. Moreover, this electronic structure is different from that of the analogous Sc3C2@Ih(7)-C80 with a (Sc3)9+(C2)3−@C806− charge distribution and no metal–metal bonding., A novel trimetallic carbide clusterfullerene, Dy3C2@Ih(7)-C80, was successfully synthesized and isolated, and the encapsulated Dy3C2 cluster adopts a bat ray configuration featuring an unprecedented three-center single-electron Dy–Dy–Dy bond.

Monometallic cyanide clusterfullerenes (CYCFs) represent a unique branch of endohedral clusterfullerenes with merely one metal atom encapsulated, offering a model system for elucidating structure-property correlation, while up to now only C