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The first theoretical investigation of the mechanisms for reactions of unsaturated hydrocarbons and the allied heterocyclic aromatics with the Si(111)-7x7 surface is reported. The density functional cluster model calculations predict stepwise, diradical pathways for these reactions.

The endohedral fullerene [Sc.sub.3]NC@[C.sub.80]-[I.sub.h] is prepared and analyzed, which has an unprecedented planar quinary cluster in a fullerene cage. The intramolecular dynamics in [Sc.sub.3]NC@[C.sub.80]-[I.sub.h] has enabled the whole molecule to exhibit high polarity and ferroelectricity.

An operable combustion method is used for preparing non-IPR fullerene, and an octahydro[60]fullerene with a non-IPR [C.sub.60] cage produced by combustion is isolated and characterized. The studies have shown that along with chlorine, hydrogen is an ample cataloreactant for the production of non-IPR fullerene derivatives under the conditions such as arc-burning and diffusion combustion.

A new [C.sub.1]-symmetric non-IPR hollow isomer, [super #23863][C.sub.78], was captured as [super #23863][C.sub.78][Cl.sub.8] and then subjected to a regioselective substitution reaction with benzyl hydroperoxide to obtain [super #23863][C.sub.78](OOC[H.sub.2][C.sub.6][H.sub.5])[Cl.sub.7]. The differences observed in in C-Cl bond length, intermediate stability, and steric effects of the involved molecules accounted for the chemical regioselectivity of the substitution reaction.

The stable compound [Sc.sub.4][C.sub.2]@[C.sub.80]-[I.sub.h] is produced and characterized as a metal carbide endofullerene by Fourier transform infrared (FTIR) and Raman spectroscopies along with density functional theory (DFT) calculations. DFT calculations have shown that this molecule has a Russian-doll-type structure, [C.sub.2]@[Sc.sub.4]@[C.sub.80].

The isolation and characterization of the [C.sub.56][Cl.sub.10] are described. The crystallographic data of [C.sub.56][Cl.sub.10] have shown an unusual Cl...Cl short contact and the alignment of pearl-necklace-like molecular chains, which can be converted into a class of useful one-dimensional fullerene polymer through regioselective reactions.

The regioselective synthesis of a Dy@[C.sub.82 ] derivative bearing a single phosphorus substituent via a zwitterion intermediate, generated by the addition of a nucleophile to an activated electrophile, is described. The new metallofullerene reaction has shown a high chemoselectivity that is different from that of [C.sub.60].

All-electron relativistic density functional computations have shown that the dimetalloendofullerene ([U.sub.2]@[C.sub.60]) has an unprecedented U-U multiple bond consisting solely of sixfold ferromagnetically coupled one-electron-two-center bonds. The bonding scheme is distinct from the metal-metal bonds, thus initiating the connection of the metal-metal multiple bonding chemistry and the fullerene chemistry.

The synthesis of a stable unconventional unconventional fullerene derivative [C.sub.64][H.sub.4] which was carried out by introducing methane in the fullerene productions with normal Kratschmer-Huffman method is described. Once the four carbon atoms at vertexes of the fused pentagon sites were chemically modified by hydrogen additions, the s[p.sup.2] to s[s.sup.3] hybridization change of the vertex carbon atoms would release remarkably the bond strains, affording the high stability of the [C.sub.64][H.sub.4] structure.

A comprehensive survey of different C-H activation pathways over various kinds of active sites of terminal oxygens [=O] and bridge oxygens [-O-] by using Mo3O9 model systems is presented. The results suggest that H abstraction is the most feasible reaction pathway for the activation of a C-H bond on molybdenum oxides and that [=O] is more active than [-O-].

A systematic density functional study on the electronic and spectroscopic properties of C50, its anions and derivatives such as C50Cl10 and C50Cl12 is performed. Findings show that both D3 and D5h isomers of C50 have high electron affinities and can be reduced easily. Due to the unstable fused pentagon structural features, C50 is chemically labile and subject to addition reactions such as chlorination, dimerization and polymerization.

A study showed that by means of density functional cluster model calculations, the adsorption of ethylene on Si(100) surface follows a diradical mechanism, proceeding visa pai-complex precursor and a singlet diradical intermediate. The calculations confirmed the scanning tunneling microscopy (STM) observation that the adsorption of an alkene on Si(100) is not stereospecific but highly stereoselective in nature.

The study conducted suggests that the central 7-7 ring fusion at the Stone-Wales defect in the (5,5) single-wall carbon nanotubes (SWNT) sidewall is less reactive than the defect-free sites. Density functional calculations using periodic boundary conditions are performed for an infinite (5,5) single-wall carbon nanotube without/with a Stone-Wales defect.

Endohedral metallofullerenes (EMFs) have been extensively studied since their discovery in 1985. Metal-metal bonds, nevertheless, have never been explicitly observed in EMFs synthesized so far. In this contribution, we show by means of all-electron relativistic density functional computations that the dimetalloendofullerene, U2@C60, has an unprecedented U-U multiple bond consisting solely of sixfold ferromagnetically coupled one-electron-two-center bonds with the electronic configuration (5fπu)²(5fσg)1- (5fδg)²(5fΦu)¹, which are dominated by the uranium 5f atomic orbitals. This bonding scheme is completely distinct from the metal-metal bonds discovered thus far in the d- and f-block polynuclear metal complexes. This finding initiates a connection of the metal-metal multiple bonding chemistry and the fullerene chemistry. [ABSTRACT FROM AUTHOR]

The viability of 1,3-dipolar cycloadditions of a series of 1,3-dipolar molecules (azomethine ylide, ozone, nitrone, nitrile imine, nitrile ylide, nitrile oxide, diazomethane, and methyl azide) onto the sidewalls of carbon nanotubes has been assessed theoretically by means of a two-layered ONIOM approach. The theoretical calculations predict the following: (i) other than the 18-valence-electron azomethine ylide and ozone, the 16-valence-electron nitrile ylide and nitrile imine are the best candidates for experimentalists to try; (ii) upon 1,3-dipolar cycloaddition, a 1,3-diople molecule is di-σ-bonded to a pair of carbon atoms on the sidewall of SWNT, forming a five-membered ring surface species; (iii) the as-formed 1,3-dipole-SWNT bonding is much weaker than that in the products of the molecular 1,3-DC reactions and can be plausibly broken by heating at elevated temperatures; (iv) the sidewalls of the armchair (n,n) SWNTs (n = 5-10) are subject to the 1,3-DCs of ozone and azomethine ylides; (v) both the 1,3-DC reactivity and retro-1,3-DC reactivity are moderately dependent on the diameters of SWNTs, implying the feasibility of making use of the heterogeneous 1,3-DC chemistry to purify and separate SWNTs diameter-specifically. [ABSTRACT FROM AUTHOR]

Quantum chemical computations show that three groups of inorganic ions and neutral molecules, whose structures have long been known and characterized, are aromatic due to through-space homoconjugation: (i) I42+, S6N42+ and S2I42+ dications and the (O2)4 cluster with pericyclic transition-state-like (PTS-like) homoaromaticity; (ii) the bishomoaromatic Te62+ and 1 ,5-diphosphadithiatetrazocines; and (iii) the spherically homoaromatic Te64+. The S2I42+ dication has an unusually high S-S bond order (∼2.3) and dual PTS-like aromaticity arising from two separate sets of four-center, six-electron (4c-6e) in-plane through-space conjugation. The diamagnetic (O2)4 structural unit recently observed in ϵ-phase oxygen solid has quadruple PTS-like aromaticity, each arising from 4c-6e in-plane through-space conjugation within an O2-O2 plane. Finally, we note that the lighter S64+ and Se64+ homologues of Te64+ also are spherically homoaromatic and might be observable in complexes. [ABSTRACT FROM AUTHOR]

C78 is one of the most widely investigated higher fullerenes. Among its huge isomer family, only one non-IPA (IPR = isolated pentagon ring) cage, the C2-symmetric #22010C78, was previously stabilized by endohedral derivatization. Here we report a new C1-symmetric non-IPR hollow isomer, #23863C78, which was captured as #23863C78 Cl8 and then subjected to a regioselective substitution reaction with benzyl hydroperoxide to form #23863C78(OOCH2C6H5)Cl7. The structural connectivity of #23863C78, which contains a pair of fused pentagons, was confirmed by single-crystal X-ray diffraction analysis of the #23863C78(OOCH2C6H5)Cl7 molecule, which shares the same fullerene core with #23863C78Cl8 support for the structure is provided by comparable IR measurements and computation. Theoretical studies suggest that the differences in C-Cl bond length, intermediate stability, and steric effects of the involved molecules account for the chemical regioselectivity of the substitution reaction. [ABSTRACT FROM AUTHOR]

Unconventional fullerenes are those smaller than C60 or those intermediate between C60 and C70, which are not stable in structure as none of the unconventional fullerene isomers satisfying the "isolated- pentagon-rule" (IPR). Below we report the synthesis of a stable unconventional fullerene derivative C64H4 by introducing methane in the fullerene productions with the normal Krätschmer-Huffman method. We also applied various spectroscopic measurements such as mass spectrometry, 13C NMR, IA, UV-vis absorption spectrometry, etc. to characterize the structural and electronic properties of this molecule, revealing an unprecedented fullerene cage with a triplet of directly fused pentagons in the framework of C64H4. Four hydrogen atoms are added to the carbons at vertexes of fused pentagons to allow the bond angles at these sites close to the sp³ tetrahedral angle, which essentially release the sp² bond strains on the abutting-pentagon sites of C64. Ab initio calculations were performed to explore the electronic property and simulate the 13C NMR and lR spectra of this fulleride, which reproduced well the experimental results and confirmed the structural assignment of the C64H4. [ABSTRACT FROM AUTHOR]

The endohedral fullerene Sc3NC@C80-Ih has been synthesized and characterized; it has an unprecedented planar quinary cluster in a fullerene cage. It is also the first chemical compound in which the presence of an unprecedented (NC)3- trianion has been disclosed. The fascinating intramolecular dynamics in Sc3NC@C80-Ih enables the whole molecule to display high polarity and promising ferroelectricity. This finding inspires the possibility that such a planar quinary cluster may be useful in constructing many other endohedral fullerenes. [ABSTRACT FROM AUTHOR]

The article focuses on a study which synthesized, isolated and characterized Sc4C82 through various methods, and demonstrated that the synthesized Sc4C82 is indeed Sc4C2@C80-Ih. The methods used in the study, such as mass spectrometry, are discussed. The study characterized Sc4C2@C80-Ih as a metal carbide endofullerene that featured a Russian-doll-type structure.

The article reports on the isolation and characterization of the C56Cl10 fullerene. According to the authors, their experiments have demonstrated the existence of a new errant in the family of smaller fullerenes. The molecular chains revealed have the potential to be converted into a class of useful one-dimensional fullerene polymer, the authors add.

The article reports on the regioselective synthesis of a derivative bearing a single phosphorus substituent via a zwitterion intermediate generated by the addition of a nucleophile to an activated electrophile. The new metallofullerene reaction shows a high chemoselectivity, markedly different from that of carbon 60.