Octafluorocyclohexa derivatives of [60]fullerene: C<Subscript>60</Subscript>(C<Subscript>4</Subscript>F<Subscript>8</Subscript>)<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 2, 3, 4, and 6)

Fluorocyclohexa adducts C₆₀(C₄F₈) _n were synthesized by high-temperature reaction of fullerene C₆₀ with 1,2-C₂F₄I₂ or 1,4-C₄F₈I₂ in sealed tubes. Their separation by HPLC allowed us to determine molecular structure (X-ray diffraction) of four new compounds C₆(C₄F₈) _n (n = 2, 3, 4, and 6). Structures of isomers C₆₀(C₄F₈) _n were discussed in terms of a concept of consecutive addition of C₄F₈ groups to the fullerene cage.     

Synthesis of a conjugate of (<Emphasis Type="Italic">R</Emphasis>)-2,2-dichloro- <Emphasis Type="Italic">N</Emphasis>-(1-phenylethyl)acetamide with fullerene C<Subscript>60</Subscript>

The Bingel–Hirsch reaction of (R)-2,2-dichloro-N-(1-phenylethyl)acetamide with fullerene C₆₀ gave the corresponding methanofullerene, and its electrochemical and physical properties were studied. The electron-acceptor characteristics of the new compound were found to be similar to those of the known methanofullerene [60]PCBM.     

The molecular designs and properties of asymmetric heterocycles (HBrBN<Subscript>3</Subscript>)<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 1-4)

The structures and properties of asymmetric heterocycles (HBrBN₃) _n (n = 1-4) are systematically studied at the B3LYP/6-31G* level. The molecules (HBrBN₃) _n (n = 2-4) have the core structures of a 2n-membered ring with alternating boron and α-nitrogen atoms. The relationships between geometrical parameters and oligomerization degree n are discussed. The calculated IR spectra have four main characteristic regions. Trends in thermodynamic properties with temperature and oligomerization degree n are discussed. Thermodynamic analysis of the gas-phase oligomerizations shows that formation of the most stable heterocycles (HBrBN₃) _n (n = 2-4) is enthalpy driven in the range of 200-800 K.     

A Systematic Search for Structures and Stabilities of Asymmetric Clusters (HfInN<Subscript>3</Subscript>)<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 1-6)

In order to find single source precursors (SSP), the structures, relative stabilities, and IR spectra of small asymmetric clusters (HFInN₃) _n (n = 1–6) are systematically investigated by means of the density functional theory at the B3LYP level. The obtained geometries show that the frameworks of clusters (HFInN₃) _n (n = 2–6) prefer to be 2n-membered ring with alternating indium and α-nitrogen atoms. The averaged binding energies reveal that all of asymmetric clusters (HFInN₃) _n (n = 1–6) can continue to gain energy as the cluster size n increasing. The second-order difference of energy (Δ₂E) and the HOMO-LUMO energy gap (E_gap) as a function of the cluster size n both exhibit a pronounced even-odd alternation phenomenon. The influences of cluster size n and temperature T on the thermodynamic properties of clusters are discussed. Judged by enthalpies and Gibbs free energies, the formations of the most stable clusters (HFInN₃) _n (n = 2–6) from the monomer are thermodynamically favorable in the range of 200–800 K.     

Low temperature radiolysis of fullerene C<Subscript>60</Subscript> and its solutions in isopropylbenzene and <Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone

Low-temperature (77 K) radiolysis of solid fullerene C₆₀ and its glassy solutions in isopropylbenzene (IPB) and N-vinylpyrrolidone (N-VP) has been investigated with the use of ESR spectroscopy. Radiationchemical yields for the formation of paramagnetic centers (G _PMC, 1/100 eV) have been determined to be ∼0.001 for pure fullerene and 0.3 and 0.7 for its solutions in IPB and N-VP, respectively. The low value of G _PMC for fullerene indicates a high stability of this form of carbon. The increase in G _PMC in solutions as compared to the pure solvents (0.15 for IPB and 0.3 for N-VP) indicates the sensitizing effect of C₆₀.     

Spatial structure and stability of Mo<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>Si<Subscript><Emphasis Type="Italic">m</Emphasis></Subscript> nanoparticles

By means of the ab initio DMol³ method Mo _n Si _m nanoparticles and fragments of Mo₃Si and MoSi₂ crystal lattices are theoretically modeled. For both crystals a few neutral Mo₄Si₆ and Mo₆Si₆ fragments of different shapes and symmetry are considered. In each case, after cluster separation its geometry is optimized, as a result of which the geometric structure noticeably changes and its stability increases. In order to theoretically search for the spatial configurations of Mo₄Si₆ and Mo₆Si₆ nanoparticle, two approaches are used: 1) in the most stable Fe₄C₆ and Fe₆C₆ isomers found previously, iron and carbon atoms are replaced by molybdenum and silicon respectively and then the geometry is optimized to obtain new equilibrium distances and angles; 2) the search for main Mo₄Si₆ and Mo₆Si₆ configurations is performed using the binominal scheme, starting from Mo₂, MoSi, and Si₂ dimers. The nanoparticle structures are found to contain metal atom chains and isolated pairs and triples of silicon atoms. In most cases, the nanoparticle stability proves to be higher than that of the crystal clusters.     

Coordination Polyhedra MC<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (M Is <Emphasis Type="Italic">s</Emphasis>-Metal Atom) in Crystal Structures

The crystallochemistry of compounds containing s-metal atoms in the carbon environment has been analyzed using the method of Voronoi–Dirichlet intersecting sectors and polyhedra. The chemical nature of the s metal has been found to affect the characteristics of the Voronoi–Dirichlet polyhedra. It is shown that the volume of Voronoi–Dirichlet polyhedron is practically independent of the coordination number of the s-metal atom.     

Structures and magnetic properties of Ni<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 36-40) clusters from first-principles calculations

A genetic algorithm (GA) coupled with a tight-binding (TB) interatomic potential is used to search for the low-energy structures of medium-sized Ni _n (n = 36-40) clusters. Structural candidates obtained from our GA search are further optimized with first-principles calculations. The medium-sized nickel clusters ranging from 36 to 40 atoms are found to favor the double-icosahedron-based structures with a Ni₇ core (a pentagonal bipyramidal structure) except Ni₃₈ cluster. The lowest-energy structure of Ni₃₈ can be considered to be a magic cluster, which is a typical face-centered cubic structure with large stability and magnetic moment.     

The smallest Hosoya index in (<Emphasis Type="Italic">n</Emphasis>, <Emphasis Type="Italic">n</Emphasis> + 1)-graphs

A (n, n + 1)-graph G is a connected simple graph with n vertices and n + 1 edges. In this paper, we determine the lower bound for the Hosoya index in (n, n + 1)-graphs in terms of the order n, and characterize the (n, n + 1)-graph with the smallest Hosoya index.     

Quantum-chemical study of C<Subscript>n</Subscript>F2<Subscript><Emphasis Type="Italic">n</Emphasis>+2</Subscript> conformers. Structure and IR spectra

Quantum-chemical calculations of the geometrical structure and vibrational spectra of C_nF_2n+2 oligomers (n = 5–8) in the chain and branched conformations are reported. The lengthening of the chain of C_nF_2n+2 does not substantially affect the geometrical parameters of the oligomers. In all cases under study, the most optimal structure of the molecule is a zigzag chain with bond lengths R(C-C) = 1.53 –1.54 and R(C-F) = 1.36 –1.34 ; the chain is rolled into a helix, which makes an angle of 17° with the plane. The IR spectra are sensitive to the structural deficiency of oligomers C_nF_2n+2 associated with the lateral trifluoromethyl groups formed in the chain; the spectra can be used for revealing defects of this type in the structure of polytetrafluoroethylene (PTFE). The possibility of defects associated with the lateral CF₃ groups in the structure of PTFE and its low-temperature modifications is explained based on the calculated total energies of C_nF2 _n+2.Original Russian Text Copyright © 2004 by L. N. Ignatieva, A. Yu. Beloliptsev, S. G. Kozlova, and V. M. BuznikTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 632–643, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Synthesis of <Emphasis Type="Italic">N</Emphasis>-and <Emphasis Type="Italic">C</Emphasis>-trimethylsilyl-substituded anililes

N-Metallation of bromoanilines with ethylmagnesium bromide followed by a reaction with trimethylchlorosilane provided N-mono and N-bis(trimethylsilyl)bromoanilines depending on the structure of substrate. The metallation of bissilylated bromoanilines with butyllithium permitted the introduction of a trimethylsilyl substituent in the aromatic ring. Previously unknown 2-bromo-N,N-bis(trimethylsilyl)aniline, 2,6-dibromo-N-trimethylsilylaniline, 2,6-dibromo-N,N-bis(trimethylsilyl)aniline, 2-bromo-6-trimethylsilylaniline, 2-bromo-6-trimethylsilyl-N,N-bis(trimethylsilyl)aniline, 2-bromo-6-trimethylsilyl-N-trimethylsilylaniline, 2,4,6-tribromo-N-trimethylsilylaniline, and 2,4,6-tribromo-N,N-bis(trimethylsilyl)aniline were prepared. The structures of the compounds obtained were established by the chromato-mass spectrometry and ¹H, ¹³C, and ²⁹Si NMR spectroscopy.     

Speciation studies of nitric acid and U(VI) third phases in <Emphasis Type="Italic">n</Emphasis>,<Emphasis Type="Italic">n</Emphasis>-dialkyl amides/<Emphasis Type="Italic">n</Emphasis>-dodecane systems

Conventionally composition of the actinide-extractant solvate is assumed to be the same in the unpartitioned organic phase and the formed third phase. For example, if a m:n solvate has formed during extraction, the solvate is expected to be in the same state even during the third phase condition. However contemporary analysis, based on the spectroscopy measurements and empirical observations, has indicated the presence of an extended solvate. In this article, the proposed speciation in nitric acid and U(VI) third phase formation in n–n dialkyl amide/dodecane-nitric acid systems has been modeled with empirical correlations.     

A quantum chemical study of the Fe@<Emphasis Type="Italic">C</Emphasis><Subscript>60</Subscript> endocomplex

At the DFT (U)PBE0/cc-pVDZ level the structural parameters of a hypothetical Fe@C ₆₀ endocomplex are determined. The (A ₁//C _3v )–Fe@C ₆₀ state characterized by the electron spin square of 3.07 au, the free valence of 4.15, the dipole moment of 1.15 D, and the 172 pm Fe nuclear shift relative to the center of inertia of С₆₀ corresponds to the energy minimum. The Stone–Wales rearrangement in the quasi-triplet state increases the endocomplex energy by 1.56 eV and by 0.79 eV in the quasi-quintet state.     

Polystyrene nanorod formation in <Emphasis Type="Italic">C</Emphasis><Subscript>12</Subscript><Emphasis Type="Italic">E</Emphasis><Subscript>5</Subscript> hemimicelle thin film templates

This paper reports the synthesis and characterization of polystyrene nanorods in hemicylindrical hemimicelles of a nonionic polyoxyethylene surfactant, C ₁₂ E ₅, on graphite. The surface structure is characterized by atomic force microscopy (AFM), Fourier transform infrared spectroscopy, and contact angle goniometry. Uniformly aligned polystyrene nanorods are captured by AFM. The nanorod dimensions are studied as a function of the reaction time and styrene monomer concentration. The template synthesis using self-assembled surfactant surface aggregates promises to create functional and stable nanostructures for optoelectronics and surface engineering.     

Synthesis of <Emphasis Type="Italic">N,N</Emphasis>-disubstituted (<Emphasis Type="Italic">Z</Emphasis>)-<Emphasis Type="Italic">O</Emphasis>-methylnicotinamide oximes

A number of (Z)-N,N-dialkyl- and (Z)-N-acyl-N-alkyl-O-methylnicotinamide oximes was synthesized. Their configuration was confirmed by the NOESY experiment. Evaluation of fungicidal activity of compounds obtained was performed.     

Isothermal solubility of individual light fullerenes in the homologous series of <Emphasis Type="Italic">n</Emphasis>-alkanes, <Emphasis Type="Italic">n</Emphasis>-alkanols, <Emphasis Type="Italic">n</Emphasis>-alkylcarboxylic acids,and arenes

Available published data on isothermal solubility (at 20°C) of individual light fullerenes in a homologous series of n-alkanes, n-alkanols, n-alkylcarboxylic acids, and arenas were systematized. A correlation between the parameter of Hildebrand’s cohesion and the logarithm of the mole fraction of the fullerene in the saturated solution was revealed.     

Synthesis of <Emphasis Type="Italic">ortho</Emphasis>-carboranyl derivatives of (<Emphasis Type="Italic">S</Emphasis>)-asparagine and (<Emphasis Type="Italic">S</Emphasis>)-glutamine

(S)-Asparagine and (S)-glutamine ortho-carboranyl derivatives with free amino and carboxy groups in the α-position were synthesized. By an example of N ^γ-(1,2-dicarba-closo-dodecarboran-3-yl)-(S)-glutamine it was demonstrated that the developed synthetic approach carboranyl derivatives of amino acids allowed the preparation of optically pure isomers.