Synthesis of an Anthraquinone-Bridged bis(terpyridine) Ligand and its Use in the Stepwise Fabrication of Complex Oligomer Wires on Gold

A new bis(terpyridine) ligand with an anthraquinone linker was synthesized. Stepwise coordination reactions at the gold surface using this ligand gave homo-metal oligomer wires up to pentamer, [ n FeL ₁ ] (n = 1–5), and hetero-metal oligomer wires with ferrocene as the terminal group, [1FeL ₁ 1FeL ₂ Fc] . Electrochemical properties of these modified electrodes were examined.     

HF-mediated equilibrium between fluorinated ketones and the corresponding α-fluoroalcohols

We have successfully obtained the first unambiguous spectroscopic proof of the structure of heptafluoropropan-2-ol by ¹³C NMR, which has been assumed from early 70s but without unequivocal evidence. Equilibrating relationship between fluorinated ketones and the corresponding hydrates as well as α-fluoroalcohols in anhydrous HF was at least qualitatively supported by our ab initio computation, and moreover, anhydrous HF as a convenient solvent was found to offer an effective new route for production of 1,1,1,3,3,3-hexafluoropropan-2-ol in industrial scales.     

Frequency offset and I/Q imbalance estimation for orthogonal frequency division multiplexing based wireless local area networks

The paper proposes a novel joint estimation of the frequency offset, frequency-independent I/Q imbalance, and frequency-dependent I/Q imbalance, using periodic pilots in orthogonal frequency division multiplexing (OFDM) based wireless local area networks (LANs). Although a low-complexity frequency offset estimation in the presence of I/Q imbalance can be obtained via a periodic pilot, the corresponding closed-form solution encounters a sign ambiguity. A method based on a power comparison between the signal and image interference is then proposed to detect the sign. Meanwhile, since one periodic pilot only is unable to estimate I/Q imbalance in the absence of a frequency offset, we also propose an estimation method based on two different periodic pilots available in the preamble. The validity and superiority of the proposed method are demonstrated by computer simulations.     

In situ small-angle neutron scattering and rheological measurements of shear-induced gelation

The microscopic structure of shear-induced gels for a mixed solution of 2-hydroxyethyl cellulose and nanometer-size spherical droplets has been investigated by in situ small-angle neutron scattering (SANS) with a Couette geometry as a function of shear rate gamma. With increasing gamma, the viscosity increased rapidly at gamma approximately 4.0 s(-1), followed by a shear thinning. After cessation of shear, the system exhibited an extraordinarily large steady viscosity. This phenomenon was observed as a shear-induced sol-gel transition. Real-time SANS measurements showed an increase in the scattering intensity exclusively at low scattering angle region. However, neither orientation of polymer chains nor droplet deformation was detected and the SANS patterns remained isotropic irrespective of gamma. It took about a few days for the gel to recover its original sol state. A possible mechanism of gelation is proposed from the viewpoint of shear-induced percolation transition.     

Structure development under transient shear flow in semidilute polystyrene solution

The shear-induced concentration fluctuations or phase separation of a semidilute solution comprised of polystyrene (PS) as a solute and dioctylphthalate (DOP) as a solvent (PS/DOP) was investigated by using real-time and in-situ shear-small-angle light scattering and shear-phase-contrast optical microscopy. When a transient shear flow with a fixed shear rate γ greater than a critical value γ_C was imposed on the solution, a unique anisotropic scattering pattern was observed some time after onset of shear. This pattern was found to be identical to the “butterfly pattern” previously reported for the same solutions under steady shear flow with γ_C. When the shear flow was ceased before the scattered intensity reached a steady state, the scattered intensity rapidly increased toward a maximum intensity, and then decreased toward the intensity of the quiescent solution with time. From the phase-contrast microscopy, this immediate increment of the scattered intensity after the shear cessation was found to arise from the increment in amplitude of the concentration fluctuations along flow direction. The characteristic length scale of the fluctuations was about 2.5 μm in this experiment, almost independent of the shear rate imposed on the solution.     

Photochrome-coupled metal complexes: molecular processing of photon stimuli

The frontiers of novel photoresponsive materials constructed with photochromes and transition metal complexes are surveyed in this review. Strategies to develop new photofunctions are categorized into four types. In the first category, intramolecular electronic interactions between photochromes and metal complexes produce entangled responses such as redox-regulated photochromic reactions or tristable photochromism. In the second, light-induced molecular structural rearrangements of photochromes induce the transformation of flexible and labile coordination structures, which can be applied to complex photomechanics or photoelectron conversion. In the third, the photochromic moiety also acts as a photonic switch, transmitting a metal-metal interaction when it is located between two metal complex moieties. The last category concerns the development of new photochromic reactions, involving metal-ligand bond rearrangements. These reactions potentially induce drastic electronic tuning of the metal center, and can be used to develop light-driven molecular machines.     

Photoresponsive molecular wires of FeII triazole complexes in organic media and light-induced morphological transformations

A lipophilic linear FeII 1,2,4-triazole complex containing azobenzene chromophores forms molecular wires in organic solvents; photoisomerization of azobenzene units induced morphological changes that lead to reversible, macroscopic gel-to-sol transition phenomena.     

High‐pressure Brillouin study of the elastic properties of rare‐gas solid xenon at pressures up to 45 GPa

The pressure dependences of three adiabatic elastic constants, adiabatic bulk modulus, refractive index, and elastic anisotropy, as well as Cauchy deviation of fcc solid Xe have been determined up to 10 GPa at 296 K by high‐pressure Brillouin scattering spectroscopy. The characteristics of elastic properties at high pressure of rare‐gas solid Xe are investigated by comparison with the previous studies on Ne, Ar, and Kr. Above 10 GPa, the occurrence of splitting in the Brillouin signals and the direction dependence of acoustic velocities for solid Xe clearly show partial phase transformation to the hcp structure reported by the previous X‐ray diffraction and Raman scattering studies. The shear elastic modulus in the hcp phase of solid Xe has also been estimated at pressures up to 45 GPa by using the pressure dependence of the Raman wavenumber shift for the E_2g mode. Copyright © 2008 John Wiley & Sons, Ltd.     

Impurity 51V nuclear relaxation in AuV Kondo alloy (TK ∼ 300K) at temperatures 78–540 K

Impurity ⁵¹V nuclear relaxation time T₁ in AuV Kondo alloys was measured in the temperature range 78–540 K, which includes the Kondo temperature T_K of ～300 K. Considerable deviation from Korringa's relation was observed.