Transition Metal/Lanthanide-Nitrogen Double Bonds Co-stabilized in a Carbon Cage.

Metal-nitrogen double bonds have been commonly reported for conventional metal complexes, but the coexistence of both transition metal-nitrogen and lanthanide-nitrogen double bonds bridged by nitrogen within one compound has never been reported. Herein, by encapsulating a ternary transition metal-lanthanide heteronuclear dimetallic nitride into a C fullerene cage, transition metal-nitrogen and lanthanide-nitrogen double bonds are costabilized simultaneously within the as-formed clusterfullerene TiCeN@C(12)-C, which is a representative heteronuclear dimetallic nitride clusterfullerene. Its molecular structure was unambiguously determined by single-crystal X-ray diffraction, revealing a slightly bent μ-bridged nitride cluster with short Ti-N (1.

Short Didysprosium Covalent Bond Enables High Magnetization Blocking Temperature of a Direct 4f-4f Coupled Dinuclear Single-Molecule Magnet.

Coupling two magnetic anisotropic lanthanide ions via a direct covalent bond is an effective way to realize high magnetization blocking temperature of single-molecule magnets (SMMs) by suppressing quantum tunneling of magnetization (QTM), whereas so far only single-electron lanthanide-lanthanide bonds with relatively large bond distances are stabilized in which coupling between lanthanide and the single electron dominates over weak direct 4f-4f coupling. Herein, we report for the first time synthesis of short Dy(II)-Dy(II) single bond (3.61 Å) confined inside a carbon cage in the form of an endohedral metallofullerene Dy@C.

A stabilization rule for metal carbido cluster bearing μ-carbido single-atom-ligand encapsulated in carbon cage.

Metal carbido complexes bearing single-carbon-atom ligand such as nitrogenase provide ideal models of adsorbed carbon atoms in heterogeneous catalysis. Trimetallic μ-carbido clusterfullerenes found recently represent the simplest metal carbido complexes with the ligands being only carbon atoms, but only few are crystallographically characterized, and its formation prerequisite is unclear. Herein, we synthesize and isolate three vanadium-based μ-CCFs featuring V = C double bonds and high valence state of V (+4), including VScC@I(7)-C, VScC@D(6)-C and VScC@D(5)-C.

Bandgap Engineering of Erbium-Metallofullerenes toward Switchable Photoluminescence.

Encapsulating photoluminescent lanthanide ions like erbium (Er) into fullerene cages affords photoluminescent endohedral metallofullerenes (EMFs). Few reported photoluminescent Er-EMFs are all based on encapsulation of multiple (two to three) metal atoms, whereas mono-Er-EMFs exemplified by Er@C are not photoluminescent due to its narrow optical bandgap. Herein, by entrapping an Er-cyanide cluster into various C cages to form novel Er-monometallic cyanide clusterfullerenes (CYCFs), ErCN@C (C (5), C (6), and C (9)), the photoluminescent properties of CYCFs are investigated, and obvious near-infrared (NIR) photoluminescence only is observed for ErCN@C (5)-C .

Steering Single-Electron Metal-Metal Bonds and Hyperfine Coupling between a Transition Metal-Lanthanide Heteronuclear Bimetal Confined in Carbon Cages.

Metal complexes bearing single-electron metal-metal bonds (SEMBs) exhibit unusual electronic structures evoking strong magnetic coupling, and such bonds can be stabilized in the form of dimetallofullerenes (di-EMFs) in which two metals are confined in a carbon cage. Up to now, only a few di-EMFs containing SEMBs are reported, which are all based on a high-symmetry icosahedral () C cage embedding homonuclear rare-earth bimetals, and a chemical modification of the -C cage is required to stabilize the SEMB. Herein, by introducing 3d-block transition metal titanium (Ti) along with 4f-block lanthanum (La) into the carbon cage, we synthesized the first crystallographically characterized SEMB-containing 3d-4f heteronuclear di-EMFs based on pristine fullerene cages.

Monometallic Endohedral Azafullerene.

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@CN] formed via fragmentation of a La@C monoadduct was detected in 1999, but the pristine MEAF has never been synthesized. Here, we report the synthesis, isolation, and characterization of the first pristine MEAF La@CN, tackling the two-decade challenge.

Capturing the Long-Sought Dy@(5)-C via Benzyl Radical Stabilization.

Endohedral metallofullerenes (EMFs) are one type of intriguing metal/carbon hybrid molecule with the molecule configuration of sphere cavity-encapsulating metal ions/metal clusters due to their unique physicochemical properties and corresponding application in the fields of biological materials, single molecule magnet materials and energy conversion materials. Although the EMF family is growing, and versatile EMFs have been successfully synthesized and confirmed using crystal structures, some expected EMF members have not been observed using the conventional fullerene separation and purify strategy. These missing EMFs raise an interesting scientific issue as to whether this is due to the difficulty in separating them from the in situ formed carbon soot.

Self-driven carbon atom implantation into fullerene embedding metal-carbon cluster.

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, VScC@ (7)-C and VScC@ (7)-C, a reasonable mechanism-C implantation (a carbon atom is implanted into carbon cage)-is proposed to interpret the evolution from VScC carbido to VScC carbide cluster.

Stabilizing a three-center single-electron metal-metal bond in a fullerene cage.

Trimetallic carbide clusterfullerenes (TCCFs) encapsulating a quinary MC 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 DyC@ (7)-C determined by single crystal X-ray diffraction shows that the encapsulated DyC cluster adopts a bat ray configuration, in which the acetylide unit C is elevated above the Dy plane by ∼1.

Capturing the Missing Carbon Cage Isomer of C via Mutual Stabilization of a Triangular Monometallic Cyanide Cluster.

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 and C cages have been isolated for the pristine CYCFs. C 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 (17)-C isomer has lower relative energy than several isolated isomers but never been found for empty and endohedral fullerenes. Herein, four novel C-based pristine CYCFs with variable encapsulated metals and isomeric cages, including MCN@(13)-C (M = Y, Dy, Tb) and DyCN@(17)-C, have been synthesized and isolated, fulfilling the first identification of the missing (17)-C isomer, which can be interconverted from the (13)-C isomer through two steps of Stone-Wales transformation.