Fullerene C as a Nanoflask that Reveals the Chemical Reactivity of Atomic Nitrogen.

To investigate the intrinsic reactivity of atomic nitrogen, which had previously been accomplished only by examining its decay in the gas phase using special equipment, a nitrogen atom was inserted into a series of molecule-encapsulating C and C fullerenes. Among the studied endofullerenes, H @C was able to encapsulate an additional nitrogen atom within the fullerene cage under radiofrequency plasma conditions. The product was analyzed by ESR spectroscopy and mass spectrometry in solution, which revealed that the nitrogen atom with a quartet ground state does not react but weakly interact with the H molecule, thus demonstrating the utility of such fullerenes as "nanoflasks".

X-ray observation of a helium atom and placing a nitrogen atom inside He@C60 and He@C70.

Single crystal X-ray analysis has been used as a powerful method to determine the structure of molecules. However, crystallographic data containing helium has not been reported, owing to the difficulty in embedding helium into crystalline materials. Here we report the X-ray diffraction study of He@C60 and the clear observation of a single helium atom inside C60.

Exceptional chemical properties of Sc@C(2v)(9)-C82 probed with adamantylidene carbene.

It has been an interesting finding that reactions of M@C(2v)(9)-C(82) (M = Y, La, Ce, Gd) with diazirine adamantylidene (AdN(2), 1) gave rise to only two monoadduct isomers, indicating that the cage reactivity of monometallofullerenes is not dependent on the type of the internal metal. However, we found here that Sc@C(2v)(9)-C(82) shows an exceptional chemical reactivity toward the electrophile 1, affording four monoadduct isomers (2a-d). Single-crystal X-ray diffraction crystallographic results of the most abundant isomer (2a) confirm that the addition takes place at a [6,6]-bond junction which is very close to the internal metal ion.

Where does the metal cation stay in Gd@C2v(9)-C82? A single-crystal X-ray diffraction study.

Metal positions in endohedral metallofullerenes (EMFs) are of special importance because their molecular symmetry and intrinsic properties are strongly influenced by the location and motion of the encapsulated metals. X-ray analyses of the cocrystals of Gd@C(2v)(9)-C(82) with nickel(II) octaethylporphyrin [Ni(II)(OEP)] reveal that the Gd(3+) cation is off-center, being located under a hexagonal ring along the 2-fold axis of the C(2v)(9)-C(82) cage. This result is in sharp contrast to that of a previous study, showing that Gd@C(2v)(9)-C(82) has an anomalous endohedral structure, with the metal being positioned over a [6,6] bond, which is opposite to the hexagonal ring along the C(2) axis (Phys.

Chemical understanding of carbide cluster metallofullerenes: a case study on Sc2C2@C2v(5)-C80 with complete X-ray crystallographic characterizations.

Little is known about the chemical properties of carbide cluster metallofullerenes (CCMFs). Here we report the photochemical reaction of a newly assigned CCMF Sc(2)C(2)@C(2v)(5)-C(80) with 2-adamantane-2,3-[3H]-diazirine (AdN(2), 1), which provides a carbene reagent under irradiation. Five monoadduct isomers (2a-2e), with respective abundances of 20%, 40%, 25%, 5%, and 10%, were isolated and characterized with a combination of experimental techniques including unambiguous single-crystal X-ray crystallography.

X-ray structures of Sc2C2@C2n (n = 40-42): in-depth understanding of the core-shell interplay in carbide cluster metallofullerenes.

X-ray analyses of the cocrystals of a series of carbide cluster metallofullerenes Sc(2)C(2)@C(2n) (n = 40-42) with cobalt(II) octaethylporphyrin present new insights into the molecular structures and cluster-cage interactions of these less-explored species. Along with the unambiguous identification of the cage structures for the three isomers of Sc(2)C(2)@C(2v)(5)-C(80), Sc(2)C(2)@C(3v)(8)-C(82), and Sc(2)C(2)@D(2d)(23)-C(84), a clear correlation between the cluster strain and cage size is observed in this series: Sc-Sc distances and dihedral angles of the bent cluster increase along with cage expansion, indicating that the bending strain within the cluster makes it pursue a planar structure to the greatest degree possible. However, the C-C distances within Sc(2)C(2) remain unchanged when the cage expands, perhaps because of the unusual bent structure of the cluster, preventing contact between the cage and the C(2) unit.

Structural elucidation and regioselective functionalization of an unexplored carbide cluster metallofullerene Sc2C2@C(s)(6)-C82.

A Sc(2)C(84) isomer, previously assumed to be Sc(2)@C(84), is unambiguously identified as a new carbide cluster metallofullerene Sc(2)C(2)@C(s)(6)-C(82) using both NMR spectroscopy and X-ray crystallography. The (13)C-nuclei signal of the internal C(2)-unit was observed at 244.4 ppm with a 15% (13)C-enriched sample.

Ferromagnetic spin coupling between endohedral metallofullerene La@C82 and a cyclodimeric copper porphyrin upon inclusion.

The cyclic host cyclo-[P(Cu)](2) carrying two covalently connected Cu(II) porphyrin units can accommodate La@C(82), a paramagnetic endohedral metallofullerene, in its cavity to form the inclusion complex cyclo-[P(Cu)](2)⊃La@C(82), which can be transformed into the caged complex cage-[P(Cu)](2)⊃La@C(82) by ring-closing olefin metathesis of its side-chain olefinic termini. On the basis of electron spin resonance (ESR) and electron spin transient nutation (ESTN) studies, cyclo-[P(Cu)](2)⊃La@C(82) is the first ferromagnetically coupled inclusion complex featuring La@C(82), whereas cage-[P(Cu)](2)⊃La@C(82) is ferrimagnetic.

Synthesis and charge-transfer chemistry of La2@I(h)-C80/Sc3N@I(h)-C80-zinc porphyrin conjugates: impact of endohedral cluster.

Two stable electron donor-acceptor conjugates, that is, 3 and 5b, employing La(2)@I(h)-C(80) and Sc(3)N@I(h)-C(80), on one hand, and zinc tetraphenylporphyrin, on the other hand, have been prepared via [1+2] cycloaddition reactions of a diazo precursor. Combined studies of crystallography and NMR suggest a common (6,6)-open addition pattern of 3 and 5b. Still, subtly different conformations, that is, a restricted and a comparatively more flexible topography, emerge for 3 and 5b, respectively.

Regioselective bis-functionalization of endohedral dimetallofullerene, La2@C80: extremal La-La distance.

Bis-functionalization of endohedral metallofullerene La(2)@C(80) by carbene addition is reported herein. Adducts were characterized using spectroscopic and single-crystal X-ray structure analyses. Crystallographic data for bisadduct La(2)@C(80)(CClPh)Ad (3, Ad = adamantylidene) revealed that both carbene additions occur at the 6,6-bond junction on the C(80) cage with ring cleavages and that La atoms are positioned collinearly with spiro carbons.

Semi-metallic single-component crystal of soluble La@C82 derivative with high electron mobility.

We prepared an organic conductor crystal having extremely high electron mobility, in which the adamantylidene (Ad) derivative of La@C(82) (an endohedral metallofullerene known as a n-type semiconductor) is aligned in an orderly fashion. The single-component crystal exhibits high electron mobility of μ > 10 cm(2) V(-1) s(-1) along the c axis under normal temperatures and pressures in the atmosphere, as shown by flash-photolysis time-resolved microwave conductivity (TRMC) measurements, which are the highest of reported organic conductors measured by TRMC. According to density functional calculations, the single crystal of La@C(82)Ad is semi-metallic, with a small band gap of 0.

Highly regioselective synthesis of bis-aziridino[60]fullerene with sulfilimine.

In the course of our study of the development of a synthetic methodology for the aziridination of fullerenes, we recently reported the photochemical [2+1] cycloaddition reaction of nitrene onto C(60) generated from sulfilimine. Sulfilimines with an electron-donating group on the N atom are well known to undergo Michael-type reactions, followed by concomitant elimination of sulfide to afford the corresponding aziridines. In these reactions, sulfilimines act as a nucleophile to the electrophilic olefins.

A molecular Ce2@I(h)-C80 switch--unprecedented oxidative pathway in photoinduced charge transfer reactivity.

We report for the first time the versatile Ce(2)@I(h)-C(80) building block toward synthesizing a novel electron donor-acceptor conjugate, Ce(2)@I(h)-C(80)-ZnP (1). A systematic investigation of the charge transfer chemistry documents a reductive charge transfer (i.e.

The effect of atomic nitrogen on the C(60) cage.

We herein report the investigation of N@C(60) exposed to laser flash excitation to exhibit the acceleration of the decay of (N@C(60))* by the encased N atom.

Regioselective exohedral functionalization of La@C82 and its 1,2,3,4,5-pentamethylcyclopentadiene and adamantylidene adducts.

The first regioselective functionalization of La@C(82) by two different groups has been performed. Bis-adducts of La@C(82) with Cp* and adamantylidene were synthesized by using two different routes and characterized. Spectroscopic analysis and theoretical calculations reveal that the addition position is controlled by the charge density and p-orbital axis vector value of the fullerene cage.

Location of the yttrium atom in Y@C82 and its influence on the reactivity of cage carbons.

The first single-crystallographic results of Y@C(82) unambiguously disclosed that the yttrium atom is located under a hexagonal ring along the C(2) axis, which makes only 1 out of 24 nonequivalent carbons of the C(2v)-C(82) sufficiently reactive toward the electrophile adamantylidene carbene, affording only two monoadduct isomers.

Missing metallofullerene with C80 cage.

Many insoluble metallofullerenes are called missing metallofullerenes. These metallofullerenes have not yet been isolated despite their detection in raw soot using mass spectrometry. They have been anticipated to show unique structures and properties that differ considerably from those of soluble metallofullerenes.

Anisotropic magnetic behavior of anionic Ce@C82 carbene adducts.

Derivatives of Ce@C(82)(C(2v)) have been synthesized and fully characterized, and their anisotropic magnetism has been observed as paramagnetic shifts in NMR measurements. Carbene addition by photochemical reaction afforded two isomers of Ce@C(82)(C(2v))Ad (Ad = adamantylidene), 2a and 2b, demonstrating high regioselectivity. The two isomers were characterized using MALDI-TOF mass spectrometry, vis-NIR absorption spectroscopy, (1)H and (13)C NMR spectroscopy, and electrochemistry.

Radical coupling reaction of paramagnetic endohedral metallofullerene La@C82.

The thermal reaction of La@C(82)(C(2v)) with 3-triphenylmethyl-5-oxazolidinone (1) in toluene affords benzyl monoadducts La@C(82)(C(2v))(CH(2)C(6)H(5)) (2a-2d). The same monoadducts are also obtained by the photoirradiation of La@C(82)(C(2v)) in toluene without the existence of 1. These reactions are applicable to paramagnetic metallofullerenes, such as La@C(82)(C(s)) and Ce@C(82)(C(2v)).