Boron-Doped Endohedral Metallofullerenes: Synthesis and Computational Analysis of a Family of Heteroatom-Doped Molecular Carbons.

Gas-phase synthesis and detection of boron-doped nitride clusterfullerenes and a large variety of monometallofullerenes have been achieved using a pulsed laser vaporization cluster source. Density functional theory (DFT) calculations show that the electronic structures of boron-doped endohedral metallofullerenes differ from those of the pristine all-carbon cages due to the lack of one electron upon boron substitution. For monometallofullerenes, this is likely the main reason for the somewhat different abundance distribution observed for boron-doped with respect to all-carbon cages.

CaY@C: Exploring Molecular Qubits with Ca-Y Metal-Metal Bonds.

Metal-metal bonding is crucial in chemistry for advancing our understanding of the fundamental aspects of chemical bonds. Metal-metal bonds based on alkaline-earth (Ae) elements, especially the heavier Ae elements (Ca, Sr, and Ba), are rarely reported due to their high electropositivity. Herein, we report two heteronuclear di-EMFs CaY@(6)-C and CaY@(5)-C, which contain unprecedented single-electron Ca-Y metal-metal bonds.

Electron-beam-promoted fullerene dimerization in nanotubes: insights from DFT computations.

Fullerene dimerization inside a peapod is analyzed at DFT level by characterizing the stationary points and deriving the energy profile of the initial and reversible process named phase 1. We find that the barriers for the radical cation mechanism are significantly lower than those found for the neutral pathway. The peapod is mainly providing one-dimensional confinement for the reaction to take place in a more efficient way.

Actinide-lanthanide single electron metal-metal bond formed in mixed-valence di-metallofullerenes.

Understanding metal-metal bonding involving f-block elements has been a challenging goal in chemistry. Here we report a series of mixed-valence di-metallofullerenes, ThDy@C (2n = 72, 76, 78, and 80) and ThY@C (2n = 72 and 78), which feature single electron actinide-lanthanide metal-metal bonds, characterized by structural, spectroscopic and computational methods. Crystallographic characterization unambiguously confirmed that Th and Y or Dy are encapsulated inside variably sized fullerene carbon cages.

U@(4)-C: A Different Cage Isomer with Reactivity Controlled by U-Sumanene Interaction.

Actinide endohedral metallofullerenes (EMFs) are a fullerene family that possess unique actinide-carbon cage host-guest molecular and electronic structures. In this work, a novel actinide EMF, U@(4)-C, was successfully synthesized and characterized, and its chemical reactivity was investigated. Crystallographic analysis shows that U@(4)-C, a new isomer of U@C, has a (4)-C cage, which has never been discovered in the form of empty or endohedral fullerenes.

Effects of Solvents on Reaction Products: Synthesis of Endohedral Metallofullerene Oxazoline and Epoxide.

Herein, we performed the reactions of MN@-C (M = Sc and Lu) with the methanol (CHOH) solution of TBAOH (note that both CHO and OH are nucleophiles) in benzonitrile (PhCN) and dimethylformamide, respectively. It is found that OH ions rather than CHO ions selectively attacked the fullerene cage to form the MN@C-O intermediate. Although the fullerene cage is initially attacked by OH in both PhCN and DMF solvents, the products are quite different.

Are U-U Bonds Inside Fullerenes Really Unwilling Bonds?

Previous characterizations of diactinide endohedral metallofullerenes (EMFs) Th@C and U@C have shown that although the two Th ions form a strong covalent bond within the carbon cage, the interaction between the U ions is weaker and described as an "unwilling" bond. To evaluate the feasibility of covalent U-U bonds, which are neglected in classical actinide chemistry, we have first investigated the formation of smaller diuranium EMFs by laser ablation using mass spectrometric detection of dimetallic U@C species with 2 ≥ 50. DFT, CASPT2 calculations, and MD simulations for several fullerenes of different sizes and symmetries showed that thanks to the formation of strong U(5f)-U(5f) triple bonds, two U ions can be incarcerated inside the fullerene.

Structurally Defined Water-Soluble Metallofullerene Derivatives towards Biomedical Applications.

Endohedral metallofullerenes (EMFs) are excellent carriers of rare-earth element (REE) ions in biomedical applications because they preclude the release of toxic metal ions. However, existing approaches to synthesize water-soluble EMF derivatives yield mixtures that inhibit precise drug design. Here we report the synthesis of metallobuckytrio (MBT), a three-buckyball system, as a modular platform to develop structurally defined water-soluble EMF derivatives with ligands by choice.

Unexpected Formation of Metallofulleroids from Multicomponent Reactions, with Crystallographic and Computational Studies of the Cluster Motion.

New multicomponent reactions involving an isocyanide, terminal or internal alkynes, and endohedral metallofullerene (EMF) Lu N@C yield metallofulleroids which are characterized by mass-spectrometry, HPLC, and multiple 1D and 2D NMR techniques. Single crystal studies revealed one ketenimine metallofulleroid has ordered Lu N cluster which is unusual for EMF monoadducts. Computational analysis, based on crystallographic data, confirm that the endohedral cluster motion is controlled by the position of the exohedral organic appendants.

Crystallographic Characterization of U@C (2 = 82-86): Insights about Metal-Cage Interactions for Mono-metallofullerenes.

Endohedral mono-metallofullerenes are the prototypes to understand the fundamental nature and the unique interactions between the encapsulated metals and the fullerene cages. Herein, we report the crystallographic characterizations of four new U-based mono-metallofullerenes, namely, U@(6)-C, U@(8)-C, U@(15)-C, and U@(12)-C, among which the chiral cages (8)-C and (12)-C have never been previously reported for either endohedral or empty fullerenes. Symmetrical patterns, such as indacene, sumanene, and phenalene, and charge transfer are found to determine the metal positions inside the fullerene cages.

Synthesis and Characterization of Two Isomers of Th@C: Th@(9)-C and Th@(5)-C.

Actinide endohedral fullerenes have demonstrated remarkably different physicochemical properties compared to their lanthanide analogues. In this work, two novel isomers of Th@C were successfully synthesized, isolated, and fully characterized by mass spectrometry, X-ray single crystallography, UV-vis-NIR spectroscopy, Raman spectroscopy, and cyclic voltammetry. The molecular structures of the two isomers were determined unambiguously as Th@(9)-C and Th@(5)-C by single-crystal X-ray diffraction analysis.

Correction: Unexpected formation of 1,2- and 1,4-bismethoxyl ScN@ -C derivatives regioselective anion addition: an unambiguous structural identification and mechanism study.

[This corrects the article DOI: 10.1039/D1SC01178B.].

Unexpected formation of 1,2- and 1,4-bismethoxyl ScN@ -C derivatives regioselective anion addition: an unambiguous structural identification and mechanism study.

An attempt to achieve heterocyclic cycloadducts of ScN@ -C reaction with PhC[double bond, length as m-dash]O, PhC[triple bond, length as m-dash]CPh or PhC[triple bond, length as m-dash]N in the presence of tetrabutylammonium hydroxide (TBAOH) stored in CHOH led to the formation of the unexpected bismethoxyl adducts of ScN@ -C ( and ). Further studies reveal that TBAOH in CHOH can boost the CHO addition efficiently, regardless of the presence of other reagents. Single-crystal X-ray diffraction results firmly assign the molecular structures of and as respective 1,4- and 1,2-bismethoxyl adducts, and reveal unusual relationships between the internal ScN cluster and the addition modes, in addition to the unusual packing mode in view of the orientation of the methoxyl groups.

UN@ (7)-C: fullerene cage encapsulating an unsymmetrical U(iv)[double bond, length as m-dash]N[double bond, length as m-dash]U(v) cluster.

For the first time, an actinide nitride clusterfullerene, UN@ (7)-C, is synthesized and fully characterized by X-ray single crystallography and multiple spectroscopic methods. UN@ (7)-C is by far the first endohedral fullerene that violates the well-established tri-metallic nitride template for nitride clusterfullerenes. The novel U[double bond, length as m-dash]N[double bond, length as m-dash]U cluster features two U[double bond, length as m-dash]N bonds with uneven bond distances of 2.

Th@(6)-C: a highly symmetric fullerene cage stabilized by a single metal ion.

A novel endohedral metallofullerene (mono-EMF), Th@D5h(6)-C80, has been successfully synthesized and fully characterized by mass spectrometry, single crystal X-ray diffraction, UV-vis-NIR and Raman spectroscopy and cyclic voltammetry. Single crystal XRD analysis unambiguously assigned the fullerene cage as D5h(6)-C80, the first example in which the highly symmetric cage is stabilized by a single metal ion. The combined experimental and theoretical studies further reveal that the D5h(6)-C80 cage, known only for its stabilization by 6-electron transfer, is stabilized by the 4-electron transfer from the encapsulated Th ion for the first time.

An Ultra-Long-Lived Triplet Excited State in Water at Room Temperature: Insights on the Molecular Design of Tridecafullerenes.

Suitably engineered molecular systems exhibiting triplet excited states with very long lifetimes are important for high-end applications in nonlinear optics, photocatalysis, or biomedicine. We report the finding of an ultra-long-lived triplet state with a mean lifetime of 93 ms in an aqueous phase at room temperature, measured for a globular tridecafullerene with a highly compact glycodendrimeric structure. A series of three tridecafullerenes bearing different glycodendrons and spacers to the C units have been synthesized and characterized.

Characterization of a strong covalent Th-Th bond inside an I(7)-C fullerene cage.

The nature of the actinide-actinide bonds is of fundamental importance to understand the electronic structure of the 5f elements. It has attracted considerable theoretical attention, but little is known experimentally as the synthesis of these chemical bonds remains extremely challenging. Herein, we report a strong covalent Th-Th bond formed between two rarely accessible Th ions, stabilized inside a fullerene cage nanocontainer as Th@I(7)-C.

A New Class of Molecular Electrocatalysts for Hydrogen Evolution: Catalytic Activity of MN@C (2 = 68, 78, and 80) Fullerenes.

The electrocatalytic properties of some endohedral fullerenes for hydrogen evolution reactions (HER) were recently predicted by DFT calculations. Nonetheless, the experimental catalytic performance under realistic electrochemical environments of these 0D-nanomaterials have not been explored. Here, for the first time, we disclose the HER electrocatalytic behavior of seven MN@2 (2 = 68, 78, and 80) fullerenes (GdN@(7)-C, YN@(7)-C, LuN@(7)-C, ScN@(7)-C, ScN@(6)-C, ScN@(5)-C, and ScN@(6140)-C) using a combination of experimental and theoretical techniques.

α-DTC Fullerene Performs Significantly Better than β-DTC as Electron Transporting Material in Perovskite Solar Cells.

In this work, two new C isomers, α and β bis(2-(thiophen-2-yl)ethyl)-C-fullerene mono-adducts (DTC), were synthesized, characterized and used as electron transporting materials (ETMs) in perovskite solar cells (PSCs). Our results show that the α isomer improves both the and FF values of the devices, when compared to the results for the β-isomer and to those for phenyl-C-butyric acid methyl ester (PCBM), used as control. Devices based on α-DTC achieved a power conversion efficiency (PCE) of 15.

Nanoscale rotational dynamics of four independent rotators confined in crowded crystalline layers.

We report a study where Car-Parrinello molecular dynamics simulations and variable-temperature (30-300 K) H spin-lattice relaxation time experiments nicely complement each other to characterize the dynamics within a set of four crystalline 1,4-diethynylbicyclo[2.2.2]octane (BCO) rotors assembled in the metal-organic rotor, {Li(CO-Ph-BCO-py)(HO)}·2DMF.

Highly selective encapsulation and purification of U-based C-EMFs within a supramolecular nanocapsule.

The ability of the tetragonal prismatic nanocapsule 1·(BArF) to selectively encapsulate U-based C EMFs from a soot mixture is reported, showing enhanced affinity for C-based EMFs over C-based EMFs. Molecular recognition driven by the electrostatic interactions between the host and guest is at the basis of the high selectivity observed for ellipsoidal C-based EMFs compared to spherical C-based EMFs. In addition, DFT analysis points towards an enhanced breathing adaptability of nanocapsule 1·(BArF) to C-based EMFs to further explain the selectivity observed when the host is used in the solid phase.

Chemical Reactions of Cationic Metallofullerenes: An Alternative Route for Exohedral Functionalization.

The chemistry of cationic forms of clusterfullerenes remain less explored than that of the corresponding neutral or anionic species. In the present work, M N@I -C (M=Sc or Lu) cations were generated by both electrochemical and chemical oxidation methods. The as-obtained cations successfully underwent the typical Bingel-Hirsch reaction that fails with neutral Sc N@I -C .

Th@C(11)-C: an actinide encapsulated in an unexpected C fullerene cage.

A novel actinide endohedral fullerene with an unexpected chiral cage, Th@C(11)-C, was synthesized and characterized. DFT calculations suggest that this low symmetry cage was favoured as a consequence of the strong interaction between Th and the cage, which makes the predictions by the ionic model less reliable for these endohedral mono-metallofullerenes.

Synthesis and Characterization of Non-Isolated-Pentagon-Rule Actinide Endohedral Metallofullerenes U@ C(17418)-C, U@ C(28324)-C, and Th@ C(28324)-C: Low-Symmetry Cage Selection Directed by a Tetravalent Ion.

For the first time, actinide endohedral metallofullerenes (EMFs) with non-isolated-pentagon-rule (non-IPR) carbon cages, U@C, Th@C, and U@C, have been successfully synthesized and fully characterized by mass spectrometry, single crystal X-ray diffractometry, UV-vis-NIR and Raman spectroscopy, and cyclic voltammetry. Crystallographic analysis revealed that the U@C and Th@C share the same non-IPR cage of C(28324)-C, and U@C was assigned to non-IPR U@ C(17418)-C. All of these cages are chiral and have never been reported before.