The Electronic Structures of (PH4)3C60 and (ClO4)3C60

Abstract

We have studied theoretically the electronic structures of a hypothetical donor-type material, (PH₄)₃C₆₀, and a hypothetical acceptor-type material, (ClO₄)₃C₆₀ from first principles by using a full-potential linear-combination-of-atomic-orbitals method based on the density-functional theory within the local-density approximation. It is found that the charge transfer from the PH₄ molecules to the C₆₀ molecules is perfect while the charge transfer from the ClO₄ molecules to the C₆₀ molecules is not perfect. We compare the latter result with the electronic structures of two typical acceptor-type organic conductors, (TMTSF)₂ClO₄ and (TMTSF)₂PF₆, and discuss the differences.     

In Situ FTIR,XPS, and STM Studies of the Nano-Structure of a Photopolymerized C60 Film

Abstract

The nano-structure of C₆₀ photopolymers has been investigated using in situ Fourier-Transform Infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning tunneling microscopy (STM). The FTTR and XPS studies revealed that the C₆₀ pholopolymer has a cross-linking via a [2+2] cycloaddition four-membered ring and formed a 2D rhombohedral structure when the polymerization was saturated. Using STM, we have successfully observed the direct real-space imaging of the C₆₀ dimers and trimers in a C₆₀ monolayer supported on a clean semiconductor surface.     

Preparation and Properties of One-Dimensional C60 Nano-Structure in a Zeolite FSM-16

Abstract

C₆₀ molecules were embedded in the pores of a zeolite FSM-16 by using a liquid phase method. The shift of photoluminescence spectra of C₆₀ solid embedded in FSM-16 was discussed using data of ESR, PDS and SAXS.     

Crystal Structure of Europium C60 Compounds

Abstract

We have studied crystal structures of europium C₆₀ compounds by high resolution x-ray diffraction measurements. In the systematic synthesis of Eu _x C₆₀ for x (0 ≤ x ≤ 6), two stable phases appear at x = 3 and 6. Eu₆C₆₀ has a bcc structure, which is an isostructure to M ₆C₆₀ (M represents an alkali or alkaline earth metal). Eu₃C₆₀ has a superstructure derived by doubling the fcc pristine C₆₀ crystal along three principal axes. This superstructure comes from an ordering of cation vacancies, which is analogous to Yb_2.75C₆₀.     

Intercalation of O2 and its Effect on the Properties of C60 and C70 Solids

Abstract

The intercalation of O₂ in C₆₀ and C₇₀ solids have been studied. In both gas effusion spectra of C₆₀ and C₇₀ powder exposed to O₂ at room temperature, two evolution peaks of O₂ are found near 80 and 150°C. In both C₆₀ and C₇₀ powder, the peak near 80°C does not depend on a heating ratio and the peak near 150°C shifts to higher temperature with the heating ratio. The activation energy on diffusion of O₂ in C₆₀ and C₇₀ solids are ～0.27eV and ～0.46eV, respectively. The number of O₂ intercalated in C₇₀ powder is larger than that in C₆₀ powder. Electron spin density of 02-intercalated C₆₀ film is larger than that of C₇₀ film. The effect on the properties of C₆₀ and C₇₀ solids by the intercalation of O₂ are discussed.     

Synthesis and structure of 4,7,13-trioxa-1,10-diaza-5,6-benzocyclopentadecane monohydrate

4,7,13-T4ioxa-1,10-diaza-5,6-benzocyclopentadecane, C₁₄H₂₂N₂O₃·H₂O (7) was synthesized by reduction of macrocyclic diamides (3) or (6). The compound crystallized in the orthorhombic space group Pbca witha=9.361(3),b=9.175(3),c=37.152(11) Å. The structure was solved by direct methods and refined to anR value of 0.048 and wR of 0.038 for 1875 reflections. The molecule itself is internally hydrogen bonded by N–H...O connections. In the crystal structures water molecules form hydrogen bonds with amine nitrogen atoms of adjacent molecules.     

A Theoretical Study of Molecular Ordering of Some Smectic Liquid Crystals

Abstract

A theoretical investigation of molecular ordering of smectic C liquuid crystals C₈H₁₇O-C₆H₄-C₆H ₄-COO-C₆H₄-OC₈H₁₇ { A }, C₉H₁₉O-C₆H₄-COO- C₆H₄-COO-C₆H₄-NO₂ { B } and its binary mixtures { A+B } has been carried out by the method based on the Rayleigth-Schrodinger perturbation theory. The mutual arrangement of two molecules corresponding to the minimum of the total interaction energy between them U_pair has been established. The curves of the dependence of U_pair and its various contributions on displacement of molecules from each other along the molecular long X-axis and angle θ between molecules' long axes has been also computed in the minimum point vicinity. The obtained results make it possible to determine the peculiarities of the structural organization of molecules, as well as to construct a model of the structure of A and B compounds in different phases taking into account the most probable packing of molecules.     

Electronic Properties of Ba-Intercalated Fullerides

Abstract

Raman spectra have been measured on Ba_xC₆₀ binary systems for x=3, 4 and 6. The pentagonal pinch Ag(2) mode exhibits a softening in an approximately proportional manner to the formal valence of C₆₀ molecule. This result suggests that the valence of C₆₀ in Ba doped systems are understood by the naive ionic crystal model based on Ba²⁺. The broader Raman peaks in superconducting Ba₄C₆₀ indicates that the electron-phonon interaction is considerably large comparing to those for Ba₃C₆₀ and Ba₆C₆₀.     

Anomalous High Pressure Properties in Fullerene Superconductors

Abstract

Correlations among lattice parameter, external pressure, and critical temperature T_c has been surveyed on fullerene superconductors with a wide range of lattice parameters and various valence states. The observed value of dT_c/dP for Na₂Rb_0.5Cs_0.5C₆₀ and Li₃CsC₆₀, having small interfullerene separations, is about a few times lager than that of K₃C₆₀. In contrast, small dT_c/dP values are found in fullerides with expanded unit cells, such as (NH₃)_xNaAA^?C₆₀ (A, A^? = K, Rb and Cs) and A₃Ba₃C₆₀. Interestingly, the chemical and physical pressure effects on T_c are considerably different in these fullerides with large interfullerene spacings. Our results suggest that the pressure dependence is scaled by an interfullerene distance when the interfullerene distances is small, but that this scaling fails when the unit cell is expanded.     

Infrared Spectra and Photoinduced Absorption of C60 Doped Polyhexylthiophene

Abstract

We report the IR spectra and the photoinduced absorption of polyhexylthiophene(PHT) doped with C₆₀. The presence of C₆₀ ^?n anions is observed in the IR spectra by a mode at 1383 cm^?1 and a broad electronic transition at 1.2 eV, while most of the C₆₀ molecules stay neutral. This is indicative that for a small fraction of C₆₀ molecules, charge transfer occurs in the ground state.

The photoinduced absorption spectra display a sharp transition at 1.15 eV peculiar to C₆₀ monoanion, the spectral features change with fullerene concentration. The intensity of the polymer photoinduced bands increases 5-10 times due to photoinduced charge transfer to C₆₀.     

Crystal Structures and Phase Transformations of the Fluorinated Fullerenes

Abstract

In situ x-ray diffraction experiments of the fluorinated fullerenes, C₆₀F _x (x = 0, 36 and 48) at high temperatures have been undertaken. The structural phase transformation of C₆₀F₄₈ was observed at about 358 K. It was also found that the lattice parameters of the low temperature phase of C₆₀F₄₈ show anomalous change at about 310 K. The thermal expansion coefficients of the fluorinated fullerenes were determined by using the change of the lattice parameters with temperature.     

Investigation of the Interaction between C60 and Si Atoms

Abstract

The interaction between C₆₀ and Si atoms was investigated using X-ray photoelectron spec-troscopy (XPS) for the photo-irradiated Si-deposited C₆₀ film in order to establish a method of a synthesis for the Si-coated C₆₀. It was found that the Cls spectrum of the photo-irradiated film contains a peak due to C-Si bonding, while no peak due to C-Si bonding was observed for the film before photo-irradiation. This indicates that Si atoms stick to C₆₀ when using the present method.     

Hydrogen Intercalation in Potassium-C60

Abstract

Solid state ¹H NMR of (KH)₃C₆₀ was measured in the temperature range between ?80 and 60 °C. A doublet spectrum composed of main peak at ?7.0 ppm and shoulder peak at ～0 ppm was observed at room temperature. The negative chemical shift of the main peak indicates that hydrogen in (KH)₃C₆₀ exists as a hydride-like ion. The 60 °C spectrum became singlet at ?5.8 ppm due to motional narrowing.     

Synthesis and structure of 4,7,13,16-tetraoxa-1,10-diaza-5,6-benzocyclooctadeca-11,18-dione monohydrate

4,7,13,16-tetraoxa-1,10-diaza-5,6-benzocyclooctadeca-11,18-dione, C₁₆H₂₂N₂O₆·H₂O, (3) was synthesized under thermal conditions, starting from ,-diamine (1) and ,-diester (2). The hydrate of compound (3) was investigated in the solid state by X-ray structural analysis. Crystal data: monoclinic system, space group P2₁/c,a=12.342(4) Å,b=15.978(7) Å,c=8.960(3) Å, =96.72(3)°,Z=4. The structure was solved by direct methods and refined to finalR=0.056,R _w=0.069 for 1962 observed reflections. The structure exhibits internal hydrogen bonds between the etheral O(16) atom and the neighboring amide group. The water molecule connects diamide molecules by one strong hydrogen bond with carbonyl oxygen, and four weak hydrogen bonds with the amide groups and etheral oxygen atoms.     

Optically Detected Magnetic Resonance (ODMR) Study of Isolated C70 Molecules and C70 Films

Abstract

The X-band ODMR of C₇₀ molecules isolated in a toluene/polystyrene (C₇₀:T/PS) glass and C₇₀ films is compared to that of C₆₀. As C₆₀:T/PS, the C₇₀ glasses exhibit only a triplet pattern at g ? 2, clearly due to an exciton delocalized over the molecule; however, it is strikingly asymmetric and narrower, due to the larger size of C₇₀. The ODMR of both C₆₀ and C₇₀ films includes a narrow photoluminescence-enhancing polaron resonance and full- and half- field narrow and broad triplet exciton patterns. As in the glasses, the narrow pattern is due to the exciton delocalized over the molecule and is narrower in C₇₀ The broad pattern is tentatively assigned to a triplet localized on a face adjacent to a neighboring molecule. In contrast to C₆₀, the ODMR of C₇₀ films is detectable up to 295 K, apparently due to the slower rotation.     

The effect of solvent ratio and water on the growth of C60 nanowhiskers

The growth of C₆₀ nanowhiskers (C₆₀NWs) prepared by a modified liquid–liquid interfacial precipitation method is investigated, focusing on the effect of solvent ratio and water content in the C₆₀–toluene–isopropyl alcohol (IPA) solution system. The precipitation of C₆₀NWs was markedly influenced by the solvent ratio of toluene to IPA, and the C₆₀NWs were found to grow longer above a critical diameter (D_c), which depends on the solvent ratio. The addition of a small amount of H₂O to the C₆₀–toluene–IPA solution promoted the growth of C₆₀NWs. This catalytic effect of water on the growth of C₆₀NWs was confirmed also by the experiment using heavy water (D₂O) and by the decrease of growth activation energy of C₆₀NWs with increase of H₂O content in the C₆₀–toluene–IPA solution.     

Synthesis and crystal structure of the coordination compound of pyridoxine with manganese sulfate

The reaction of pyridoxine with manganese sulfate in an aqueous solution gave the coordination compound MnSO₄ · 2C₈H₁₁O₃N · 2H₂O (I). The structure of I was determined from single-crystal X-ray diffraction data. In the centrosymmetric complex (sp. gr. P[`1]P\bar 1, Z = 1), the Mn atom is coordinated by two pyridoxine molecules and two water molecules, thus adopting an octahedral coordination. The sulfate anion is also at a center of symmetry and, consequently, is disordered. The pyridoxine molecules are coordinated to the metal atom through the oxygen atoms of the deprotonated hydroxyl group and the CH₂OH group that retains the hydrogen atom. The nitrogen atom is protonated in such a way that the heterocycle assumes a pyridinium character. The crystal structure also contains six water molecules of crystallization. A thermogravimetric study showed that the decomposition of I occurs in several successive steps, such as dehydration, the combustion of organic ligands, and the formation of an inorganic residue.     

Structural Influence on the Intensitiy Ratio of the T′ and T87Rb NMR Lines and the Superconductivity in Rb3C60

Abstract

The intensity ratio of the T′/T⁸⁷Rb NMR lines in Rb₃C₆₀ could be changed by different cooling rates after annealing at 380 °C. The results are discussed with respect to magnetically different surroundings of the Rb ions through the two standard orientations of the C₆₀ ^3-ions. Additionally, the superconducting volume fraction is influenced by the different cooling procedures.     

Electron Transfer and Energy Transfer Reactions in Photoexcited α-Nonathiophene/C60 Films and Solutions

Abstract

Photoexcitation of a nonathiophene in film or solution across the π-π* energy gap produces a metastable triplet state. In the presence of C₆₀, on the other hand, an ultra fast electron transfer from the photoexcited nonathiophene onto C₆₀ is observed in films, whereas in solution C₆₀ is involved in an efficient energy transfer reaction with the triplet-state nonathiophene.     

X-ray structure and NMR assignment of 4,4′-[3-oxa-1,5-pentanedi(ylthio)]-3,3′-diquinolinyl sulfide

The title compound (C₂₂H₁₈N₂OS₃) is monoclinic, with a=20.7446(5), b=8.332(1), c=24.393(7)°, β=112.12(1)° and space group P2₁/n. There are two independent molecules in the unit cell. Two quinoline moieties are nearly perpendicular to each other (76.9(1)°) and (72.0(2)°). Both S-methylene fragments are trans-orientated with respect to the C(3)−S(1)−C(13) plane. Two pairs of sulfur atoms in ortho-positions are in very close contact with sulfide preserving a skew conformation. The central 12-membered ring adopts an unusual conformation. Part XLIII in the series of Azinyl Sulfides. Part XLII: Maślankiewicz, M.J.; Maślankiewicz, A.J. Heterocycl. Chem. 1996,33, 1989.