Partial Charge Transfer in the Shortest Possible Metallofullerene Peapod,La@C82⊂[11]Cycloparaphenylene

[11]Cycloparaphenylene ([11]CPP) selectively encapsulates La@C₈₂ to form the shortest possible metallofullerene–carbon nanotube (CNT) peapod, La@C₈₂?[11]CPP, in solution and in the solid state. Complexation in solution was affected by the polarity of the solvent and was 16 times stronger in the polar solvent nitrobenzene than in the nonpolar solvent 1,2‐dichlorobenzene. Electrochemical analysis revealed that the redox potentials of La@C₈₂ were negatively shifted upon complexation from free La@C₈₂. Furthermore, the shifts in the redox potentials increased with polarity of the solvent. These results are consistent with formation of a polar complex, (La@C₈₂)^δ??[11]CPP^δ+, by partial electron transfer from [11]CPP to La@C₈₂. This is the first observation of such an electronic interaction between a fullerene pea and CPP pod. Theoretical calculations also supported partial charge transfer (0.07) from [11]CPP to La@C₈₂. The structure of the complex was unambiguously determined by X‐ray crystallographic analysis, which showed the La atom inside the C₈₂ near the periphery of the [11]CPP. The dipole moment of La@C₈₂ was projected toward the CPP pea, nearly perpendicular to the CPP axis. The position of the La atom and the direction of the dipole moment in La@C₈₂?[11]CPP were significantly different from those observed in La@C₈₂?CNT, thus indicating a difference in orientation of the fullerene peas between fullerene–CPP and fullerene–CNT peapods. These results highlight the importance of pea–pea interactions in determining the orientation of the metallofullerene in metallofullerene–CNT peapods.     

Ligand‐Controlled Synthesis of [3]‐ and [4]Cyclo‐9,9‐dimethyl‐2,7‐fluorenes through Triangle‐ and Square‐Shaped Platinum Intermediates

The syntheses of [3]‐ and [4]cyclo‐9,9‐dimethyl‐2,7‐fluorenes ([3] and [4]CFRs), cyclic trimer, and tetramers of 9,9‐dimethyl‐2,7‐fluorene (FR), respectively, were achieved by the platinum‐mediated assembly of FR units and subsequent reductive elimination of platinum. A triangle‐shaped tris‐platinum complex and a square‐shaped tetra‐platinum complex were obtained by changing the platinum ligand. The structure of the triangle complex was unambiguously determined by X‐ray crystallographic analysis. Reductive elimination of each complex gave [3] and [4]CFRs. Two rotamers of [3]CFR were sufficiently stable at room temperature and were separated by chromatography. The physical properties of the CFRs were also investigated theoretically and experimentally.     

Damage evaluation of sheet moulding compound composite by acoustic emission

The acoustic emission technique is applied to detect and assess damage in notched specimens made of short fiber-reinforced sheet moulding compound (SMC) composite. Acoustic emission (AE) counts and energy are identified with damage growth ahead of the notch tip. Stress intensification over a local region can be measured by the factor K₁, while unstable growth is assumed to correspond with the critical condition of an inner region. The former is referred to as the primary-damage zone and the latter as the secondary-damage zone. AE data, correlated with the sizes of the damage zones and intensities of the notch tip stress field, are presented.     

Production of spin polarized 12N through heavy ion reactions

The structural and magnetic properties of Ho substituted BiFeO₃ (BHFO) have been investigated using ⁵⁷Fe Mössbauer spectroscopy and X-Ray diffraction (XRD) as a function of temperature. The Mössbauer spectrum obtained at room temperature for the as-synthesized BHFO sample exhibits broadened features due to the hyperfine field distributions related to the local variation of the neighbourhood of Fe and the magnetic hyperfine splitting patterns are indicative of magnetic ordering, mostly probably screwed or slightly antiferromagnetic. The spectrum was fitted with two superimposed asymmetric sextets, with similar hyperfine magnetic fields of B_hf1 = 48.0(1) T and B_hf2 = 49.0(1) T, corresponding to rhombohedral BFO. The hyperfine fields of the magnetic components decreased systematically with increasing temperature to a ‘field distribution’ just below the Néel temperature, T_N ~ 600 K. At temperatures above 600 K, the spectral line associated with the Bi₂₅FeO₄₀ impurity phase dominates the spectra. This phase is confirmed by XRD measurements. From the temperature dependence of the site populations of the spectral components an average Debye temperature of θ _D = 240(80) K has been estimated.     

Spin polarization of 29P produced through low energy nuclear reaction

Spin polarization of short-lived β-emitting nucleus ²⁹P (I ^π = 1/2^?+?, T _1/2 = 4.14 s) produced through the ²⁸P(d, n) ²⁹P reaction was studied as functions of the incident deuteron energy E _d and the recoil angle θ of ²⁹P. New optimum condition was found at E _d = 3.3 MeV and θ = 30° where polarization of ²⁹P is ?(4.1 ± 0.7) %.     

L12 phase formation and giant exchange anisotropy in Mn3Ir/Co–Fe bilayers

The degree of order S of Mn–Ir layers and the exchange anisotropy of Mn–Ir/Co–Fe bilayers were investigated for various chemical compositions of Mn–Ir layers, underlayer materials, and underlayer thicknesses. It was found that: (1) The compositional range over which L1₂-phase Mn₃Ir could be formed is 22–32 at% Ir and giant exchange anisotropy is obtained in this range. (2) Ru is favorable as an underlayer material for avoiding interdiffusion with the Mn–Ir layer during deposition on the temperature elevated substrate. (3) The underlayer thickness could be reduced to 5 nm while maintaining a giant exchange anisotropy in excess of 1 erg/cm².     

Anomalous electric-field dependence of excitonic Fano-resonance spectra in semiconductor quantum-wells

Optical absorption spectra due to Fano resonance (FR) of an exciton in a quantum well with an external electric field perpendicular to the layer plane are presented, based on multi-channel scattering calculations incorporating a hole-subband mixing effect. Peak values of the calculated FR spectra exhibit anomalous field-dependent changes. These cannot be accounted for by the commonly-known quantum-confined Stark effect (QCSE) that has been applied exclusively to bound state spectra. This behavior, ascribable to correlation between Fano couplings and the QCSE, is revealed just in high-resolution spectra, otherwise the field-dependence results in nothing but the same as that of the bound-state spectra.     

Ferroelectric-relaxor behavior of (Na0.5K0.5)NbO3-based ceramics

We report that ferroelectric-relaxor behavior is induced by doping of SrO and TiO₂, or BaO and TiO₂ into classic ferroelectric (Na_0.5K_0.5)NbO₃. It is found that [(Na_0.5K_0.5)_0.9Sr_0.1](Nb_0.9Ti_0.1)O₃ ceramics exhibit a pronounced ferroelectric-relaxor behavior, comparable to that of [(Na_0.5K_0.5)_0.9Ba_0.1](Nb_0.9Ti_0.1)O₃ ceramics. Our results indicate that the relaxor behavior is closely related to the appearance of micropolar regions in these systems. The relaxor behavior should arise from the dynamic response of micropolar clusters. Raman spectra of [(Na_0.5K_0.5)_1−xSr_x](Nb_1−xTi_x)O₃ ceramics measured in the wavenumber range from 100 to 1200 cm⁻¹ confirm that the first order scattering is dominant in phonon bands should result from both short-range ordered region (micropolar regions) and disordered matrix. The frequency dependence of dielectric permittivity measurements show that the relaxor behavior of SrO and TiO₂, or BaO and TiO₂ doped (Na_0.5K_0.5)NbO₃ ceramics is not a Debye type in the radio frequency range.     

Chemical and morphological evolution of supported Ru nanoparticles during oxidative conversion of methane

Alumina supported Ru nanoparticles, with an initial average size of 5.8 nm, show high activity and yield to CO and H₂ at lower temperature than the conventionally prepared catalysts. This revised version was published online in June 2006 with corrections to the Cover Date.