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Chemical reduction of the Li + @C 60 cation by decamethylferrocene was carried out to obtain neutral Li + @C 60 •– (simply denoted as Li@C 60 ). The method is scalable and does not demand long reaction times unlike electrolytic reduction routes. Powder X-ray diffraction and Raman and EPR spectroscopic measurements of the Li@C 60 solid sample are consistent with the presence mainly of (Li@C 60 ) 2 dimers together with remaining Li + @C 60 •– monomer species due to lack of crystallization time in the course of formation and precipitation.

We investigated the pressure dependence of electric transport in a superconducting sample, Ba

The [10]phenacene and [11]phenacene molecules have been synthesized using a simple repetition of Wittig reactions followed by photocyclization. Sufficient amounts of [10]phenacene and [11]phenacene were obtained, and thin-film FETs using these molecules have been fabricated with SiO2 and ionic liquid gate dielectrics. These FETs operated in p-channel. The averaged measurements of field-effect mobility, <μ>, were 3.1(7) × 10−2 and 1.11(4) × 10−1 cm2 V−1 s−1, respectively, for [10]phenacene and [11]phenacene thin-film FETs with SiO2 gate dielectrics. Furthermore, [10]phenacene and [11]phenacene thin-film electric-double-layer (EDL) FETs with ionic liquid showed low-voltage p-channel FET properties, with <μ> values of 3(1) and 1(1) cm2 V−1 s−1, respectively. This study also discusses the future utility of the extremely extended π-network molecules [10]phenacene and [11]phenacene as the active layer of FET devices, based on the experimental results obtained.

Molecular solids with cooperative electronic properties based purely on π electrons from carbon atoms offer a fertile ground in the search for exotic states of matter, including unconventional superconductivity and quantum magnetism. The field was ignited by reports of high-temperature superconductivity in materials obtained by the reaction of alkali metals with polyaromatic hydrocarbons, such as phenanthrene and picene, but the composition and structure of any compound in this family remained unknown. Here we isolate the binary caesium salts of phenanthrene, Cs(C

The most expanded fcc-structured alkali fulleride, Cs3C60, is a Mott insulator at ambient pressure because of the weak overlap between the frontier t1u molecular orbitals of the C603− anions. It has a severely disordered antiferromagnetic ground state that becomes a superconductor with a high critical temperature, Tc of 35 K upon compression. The effect of the localised t1u3 electronic configuration on the properties of the material is not well-understood. Here we study the relationship between the intrinsic crystallographic C603− orientational disorder and the molecular Jahn–Teller (JT) effect dynamics in the Mott insulating state. The high-resolution 13C magic-angle-spinning (MAS) NMR spectrum at room temperature comprises three peaks in the intensity ratio 1:2:2 consistent with the presence of three crystallographically-inequivalent carbon sites in the fcc unit cell and revealing that the JT-effect dynamics are fast on the NMR time-scale of 10−5 s despite the presence of the frozen-in C603− merohedral disorder disclosed by the 133Cs MAS NMR fine splitting of the tetrahedral and octahedral 133Cs resonances. Cooling to sub-liquid-nitrogen temperatures leads to severe broadening of both the 13C and 133Cs MAS NMR multiplets, which provides the signature of an increased number of inequivalent 13C and 133Cs sites. This is attributed to the freezing out of the C603− JT dynamics and the development of a t1u electronic orbital glass state guided by the merohedral disorder of the fcc structure. The observation of the dynamic and static JT effect in the Mott insulating state of the metrically cubic but merohedrally disordered Cs3C60 fulleride in different temperature ranges reveals the intimate relation between charge localization, magnetic ground state, lifting of electronic degeneracy, and orientational disorder in these strongly-correlated systems.

The hyperexpanded (CH3NH2)K3C60 fulleride and its perdeuterated analogue were investigated by 1H and 2H NMR spectroscopy between room temperature and 4 K. Two phase transitions at TS = 220 K and TN = 11 K clearly were detected in the temperature dependence of the NMR line shapes, the spectral first (M1) and second (M2) moments, and the spin lattice relaxation times, T1. From 2H NMR line shape analysis, we found that the structural phase transition at TS was driven by the freezing out of the discrete Markovian-type jump motion of the entire K+-ND2CD3 unit that is characterized by an activation energy, Ea = 236(51) meV. Below TS, a sudden change in the temperature dependence of M1 suggests the appearance of a small but nonzero spin density on the K+-NH2CH3 unit. This could influence the electronic properties of the fulleride phase by modulating the strength of the exchange interactions between C603− anions and controlling the width, W, of the t1u-derived band. The 1H NMR spectra below TN show significant li...

The electron paramagnetic resonance (EPR) technique is used to study the temperature evolution of the electronic and magnetic properties of the hyperexpanded fulleride (CH 3 NH 2 )K 3 C 60 in the temperature range 4-294 K. Unambiguous signatures for the development of large internal magnetic fields and a transition to an antiferromagnetic ground state below T N = 11 K are provided by the temperature dependence of the spin susceptibility, the EPR line width, and the position of the EPR line. The EPR results in the paramagnetic regime are indicative of an insulating electronic state, with localized S = 1/2 moments on the C 60 3- ions. The accompanying complex evolution of the spin susceptibility, EPR line width, and g-factor anisotropy furthermore reveals that effects of electronic origin (t 1u orbital order-disorder transition, crossover from static to dynamic Jahn-Teller distortions) in the vicinity of the structural transformation are important for the understanding of the exchange interactions between the fulleride ions.

X-ray diffractions and electronic transports for the Ce@C82 isomers I and II, which refer to major and minor isomers, respectively, are studied in a wide temperature region to clarify the structura...

The alkali fullerides, A(3)C(60) (A = alkali metal) are molecular superconductors that undergo a transition to a magnetic Mott-insulating state at large lattice parameters. However, although the size and the symmetry of the superconducting gap, Δ, are both crucial for the understanding of the pairing mechanism, they are currently unknown for superconducting fullerides close to the correlation-driven magnetic insulator. Here we report a comprehensive nuclear magnetic resonance (NMR) study of face-centred-cubic (f.c.c.) Cs(3)C(60) polymorph, which can be tuned continuously through the bandwidth-controlled Mott insulator-metal/superconductor transition by pressure. When superconductivity emerges from the insulating state at large interfullerene separations upon compression, we observe an isotropic (s-wave) Δ with a large gap-to-superconducting transition temperature ratio, 2Δ0/k(B)T(c) = 5.3(2) [Δ0 = Δ(0 K)]. 2Δ0/k(B)T(c) decreases continuously upon pressurization until it approaches a value of ~3.5, characteristic of weak-coupling BCS theory of superconductivity despite the dome-shaped dependence of Tc on interfullerene separation. The results indicate the importance of the electronic correlations for the pairing interaction as the metal/superconductor-insulator boundary is approached.

aJASRI, SPring-& Mikazuki, Sayo-gun, Hyougo 679-5198, Japan, bRIKEN, SPring-& Kamigori, Ako-gun, Hyougo 6795198, Japan, CjAERI Kansai, SPring-& Mikazuki, Sayogun, Hyougo 679-5143, Japan, dlnstitute of Scientific and Industrial Reseach, Osaka University, Ibaraki, Osaka 5670047, Japan, eFaculty of Science, Okayama University, Okayama 700, Japan, tDepartment of Molecular Engineering, Kyoto University, Kyoto 606-5801, Japan, gFaculty of Science, Osaka University, Toyonaka, Osaka 560, Japan, "Fundamental Research Laboratry, NEC, Tsukuba, Ibaragi 305, Japan. Emaihurugat@springS.or.jp