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.

Dicyanometalates as Building Blocks for Multinuclear Iron(II) Spin-Crossover Complexes.

A synthetic strategy featuring dicyanometalates [M(CN)] (M = Ag, Au) as N-coordinating ditopic linkers connecting partially blocked Fe centers has been employed to produce heterometallic hexanuclear complexes, which exhibit spin-crossover (SCO) behavior at the Fe sites. The reaction between tris(2-pyridylmethyl)amine (tpma)-capped Fe ions and [Ag(CN)] proceeded with partial decomposition of the dicyanoargentate and led to the formation of {[Fe(tpma)](μ-CN)[μ-Ag(CN)]}(ClO)·3HO (), in which both [Ag(CN)] and CN act as bridging ligands, and the opposite [Ag(CN)] bridges are engaged in a pronounced argentophilic d-d interaction. In an analogous synthesis, the more stable [Au(CN)] species remained intact and furnished the complex {[Fe(tpma)][μ-Au(CN)]} (), which features two Fe centers bridged by two [Au(CN)] dimers.

Transformation of doped graphite into cluster-encapsulated fullerene cages.

An ultimate goal in carbon nanoscience is to decipher formation mechanisms of highly ordered systems. Here, we disclose chemical processes that result in formation of high-symmetry clusterfullerenes, which attract interest for use in applications that span biomedicine to molecular electronics. The conversion of doped graphite into a C cage is shown to occur through bottom-up self-assembly reactions.

Regiochemically Controlled Synthesis of a β-4-β' [70]Fullerene Bis-Adduct.

A β-4-β' C bis-adduct regioisomer and an uncommon mono-adduct β-malonate C derivative were synthesized by using a Diels-Alder cycloaddition followed by an addition-elimination of bromo-ethylmalonate and a retro-Diels-Alder cycloaddition reaction. We also report the regioselective synthesis and spectroscopic characterization of C-symmetric tris- and C-symmetric tetra-adducts of C, which are the precursors of the mono- and bis-adduct final products.

Small endohedral metallofullerenes: exploration of the structure and growth mechanism in the Ti@C (2 = 26-50) family.

The formation of the smallest fullerene, C, was recently reported using gas phase experiments combined with high-resolution FT-ICR mass spectrometry. An internally located group IV metal stabilizes the highly strained non-IPR C cage by charge transfer (IPR = isolated pentagon rule). Ti@C also appeared as a prominent peak in the mass spectra, and U@C was demonstrated to form by a bottom-up growth mechanism.

Bottom-up formation of endohedral mono-metallofullerenes is directed by charge transfer.

An understanding of chemical formation mechanisms is essential to achieve effective yields and targeted products. One of the most challenging endeavors is synthesis of molecular nanocarbon. Endohedral metallofullerenes are of particular interest because of their unique properties that offer promise in a variety of applications.

Spin crossover in tetranuclear Fe(II) complexes, {[(tpma)Fe(μ-CN)]4}X4 (X = ClO4(-), BF4(-)).

Two Fe(II) complexes, {[(tpma)Fe(μ-CN)]4}X4 (X = ClO4(-) (1a), BF4(-) (1b); tpma = tris(2-pyridylmethyl)amine), were prepared by reacting the {Fe(tpma)}(2+) building block with (Bu4N)CN. The crystal structures of 1a and 1b feature a tetranuclear cation composed of cyanide-bridged Fe(II) ions, each capped with a tetradentate tpma ligand. The Fe4(μ-CN)4 core of the complex is strongly distorted, assuming a butterfly-like geometry.

Metallofullerene and fullerene formation from condensing carbon gas under conditions of stellar outflows and implication to stardust.

Carbonaceous presolar grains of supernovae origin have long been isolated and are determined to be the carrier of anomalous (22)Ne in ancient meteorites. That exotic (22)Ne is, in fact, the decay isotope of relatively short-lived (22)Na formed by explosive nucleosynthesis, and therefore, a selective and rapid Na physical trapping mechanism must take place during carbon condensation in supernova ejecta. Elucidation of the processes that trap Na and produce large carbon molecules should yield insight into carbon stardust enrichment and formation.

Charge reversal Fourier transform ion cyclotron resonance mass spectrometry.

We report the first charge reversal experiments performed by tandem-in-time rather than tandem-in-space MS/MS. Precursor odd-electron anions from fullerene C(60), and even-electron ions from 2,7-di-tert-butylfluorene-9-carboxylic acid and 3,3'-bicarbazole were converted into positive product ions ((-)CR(+)) inside the magnet of a Fourier transform ion cyclotron resonance mass spectrometer. Charge reversal was activated by irradiating precursor ions with high energy electrons or UV photons: the first reported use of those activation methods for charge reversal.

Formation of heterofullerenes by direct exposure of C60 to boron vapor.

Introducing boron: heterofullerenes that incorporate boron have been scarcely studied because a formation route from C(60) is not known. It is now reported that C(59)B(-), an electronically closed-shell species, is formed directly from pristine C(60) in the gas-phase by facile atom exchange reactions.

Closed network growth of fullerenes.

Tremendous advances in nanoscience have been made since the discovery of the fullerenes; however, the formation of these carbon-caged nanomaterials still remains a mystery. Here we reveal that fullerenes self-assemble through a closed network growth mechanism by incorporation of atomic carbon and C(2). The growth processes have been elucidated through experiments that probe direct growth of fullerenes upon exposure to carbon vapour, analysed by state-of-the-art Fourier transform ion cyclotron resonance mass spectrometry.

The smallest stable fullerene, M@C28 (m = Ti, Zr, U): stabilization and growth from carbon vapor.

The smallest fullerene to form in condensing carbon vapor has received considerable interest since the discovery of Buckminsterfullerene, C(60). Smaller fullerenes remain a largely unexplored class of all-carbon molecules that are predicted to exhibit fascinating properties due to the large degree of curvature and resulting highly pyramidalized carbon atoms in their structures. However, that curvature also renders the smallest fullerenes highly reactive, making them difficult to detect experimentally.