In Situ FT-IR Study of an Electron-Beam Induced Reaction of C60 Film

Abstract

The structural modification induced by electron-beam (EB) in a C₆₀ film and its kinetics have been studied using in situ high-resolution FT-IR spectroscopy. Similar to studies on photoirradiated K_xC₆₀ fim, was found that a coalescence reaction between adjacent C₆₀ molecules takes place. In order to investigate the interaction between an incident electron and Cgg molecules, the time-dependence of the amounts of C₆₀ on the EB irradiation was examined. It was found that the reaction rate exhibits a linear dependence on the reactant concentration and nonlinear dependence on the incident current.     

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.     

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.     

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.     

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.     

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.     

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 Characterization of Fullerene-Metal Compound with Long Alkyl Chain for Liquid Crystals,Supramolecules, and Optoelectronic Materials

A novel C₆₀-Os₃ (carbon-metal) compound with long alkyl chain, Os₃(CO)₈[(C₁₆H₃₃O)₃C₆H₂NC](μ₃-η²:η²:η²-C₆₀) (2), was synthesized by substituted reaction between one CO of Os₃(CO)₉(μ₃-η²:η²:η²-C₆₀) and (C₁₆H₃₃O)₃C₆H₂NC (1). Compound 1 and 2 have been characterized by IR and ¹H NMR. Cyclic voltammetry (CV) and differential scanning calorimetry (DSC) were performed to electrochemical property and phase transition of 2.     

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.     

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.     

Can Two-Dimensional Fullerene Polymers Be Intercalated?

Abstract

Two-dimensional C₆₀ polymers can be produced by treatment at high T and high p. Attempts have previously been made to intercalate these layered materials by alkali metals using the gas phase method but the polymers have always decomposed. We investigate here whether intercalated 2D polymers can be formed by other methods, such as by polymerization in the presence of alkali metals. Preliminary x-ray and Raman data can be interpreted to indicate the presence of an alkali metal intercalated tetragonal fullerene polymeric structure.     

Occupied and Unoccupied Orbitals of C60 and C70

Abstract

The full spectrum of occupied and unoccupied σ and π orbitals is presented for solid C₆₀, C₇₀, and graphite, using Cls emission and absorption spectroscopy. There are significant diffcrences between C₆₀ and C₇₀, and even larger changes relative to their infinite analog graphite (C∝). A comparison is made with photocmission and inverse photoemission results, along with first principles quasiparticle calculations.     

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.     

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.     

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.     

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.     

X-Ray Diffraction and Physical Properties of Potassium Fullerides KxC70

Abstract

X-ray diffraction and magnetic-susceptibility measurements have been carried out for single phase K_xC₇₀ (x=1, 3, 4, 6 and 9) compounds synthesized by heating stoichiometric amount of K₉C₇₀ and C₇₀. The x-ray diffraction profiles show no structural transition down to 10K. The fairly large temperature-independent paramagnetic contribution was observed in x=3 and 4. The electrical resistivity has been measured for K evaporated C₇₀ film with increasing K thickness. Two resistivity minima were observed at x=1 and 4.     

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.     

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.