Synthesis and structural characterisation of a cationic trinuclear organobismuth complex with an unprecedented coordination mode of hydrotris(2-mercaptoimidazolyl)borate ligands

A new coordination mode of hydrotris(2-mercaptoimidazolyl)borate ligands was found in the reaction of [Na(Tm(tBu))] with Me(2)BiCl to form a trinuclear organobismuth complex [(Me(2)Bi)(3)(Tm(tBu))(2)](+)[Me(2)BiCl(2)](-)(Tm(tBu)= hydrotris(2-mercapto-1-tert-butylimidazolyl)borate).     

Temperature dependence of formation of nanorods and dots of iodine compounds on an H-terminated Si(111) surface in a concentrated HI solution

Immersion of atomically flat, H-terminated Si(111) surfaces in 7.6 M HI for 0.5 - 4 h caused spontaneous formation of nanosized clusters at the Si surface. X-ray photoelectron spectroscopy analysis suggested that the clusters were composed of silicon iodides (such as SiHxI4-x), produced most probably by Si etching with HI. Atomic force microscopy inspection revealed that the immersion at a low temperature below about 30 degrees C led to the formation of long rod-shaped clusters, oriented in the (112) direction or equivalents, whereas the immersion at a high temperature above 30 degrees C led to the formation of circular dot clusters, their size and shape changing abruptly at about 70 degrees C. It is shown experimentally that the formation of dot clusters at a high immersion temperature is explained on the basis of thermodynamics, whereas that of oriented rod clusters at a low temperature is explained by a kinetics-controlled mechanism.     

Development of a zinc ion-selective luminescent lanthanide chemosensor for biological applications

Detection of chelatable zinc (Zn(2+)) in biological studies has attracted much attention recently, because chelatable Zn(2+) plays important roles in many biological systems. Lanthanide complexes (Eu(3+), Tb(3+), etc.) have excellent spectroscopic properties for biological applications, such as long luminescence lifetimes of the order of milliseconds, a large Stoke's shift of >200 nm, and high water solubility. Herein, we present the design and synthesis of a novel lanthanide sensor molecule, [Eu-7], for detecting Zn(2+). This europium (Eu(3+)) complex employs a quinolyl ligand as both a chromophore and an acceptor for Zn(2+). Upon addition of Zn(2+) to a solution of [Eu-7], the luminescence of Eu(3+) is strongly enhanced, with high selectivity for Zn(2+) over other biologically relevant metal cations. One of the important advantages of [Eu-7] is that this complex can be excited with longer excitation wavelengths (around 340 nm) as compared with previously reported Zn(2+)-sensitive luminescent lamthanide sensors, whose excitation wavelength is at too high an energy level for biological applications. The usefulness of [Eu-7] for monitoring Zn(2+) changes in living HeLa cells was confirmed. This novel Zn(2+)-selective luminescent lanthanide chemosensor [Eu-7]should be an excellent lead compound for the development of a range of novel luminescent lanthanide chemosensors for biological applications.     

Clove oil prevents glycyrrhizin gel formation in aqueous solution

One persistent problem with using therapeutic concentrations of glycyrrhizin (GZ) is that, at these high concentrations, it forms a gel in an aqueous solution. We previously solved this problem by dissolving GZ in a highly concentrated phosphate buffer. Unfortunately, the resulting GZ solution has a hyperosmotic pressure that renders it unsuitable for use in patients. The aim of this study was to prepare a highly concentrated GZ solution having an osmotic pressure ratio of 1 and a pH of 7.4. By adding small amounts of oil and using a 100 mM phosphate buffer, we achieved an emulsified GZ solution that is stable at room temperature and has a physiological osmotic pressure and pH. When clove oil was used as an emulsifier, the gel formation temperature of GZ solution decreased appreciably compared to that of GZ solution without clove oil. Using scanning electron microscopy (SEM), we examined the detailed characteristics of GZ gels prepared from solutions with or without clove oil. SEM of cross sections of GZ gels revealed an irregular structure in gels prepared with clove oil, indicating that clove oil prevented the formation of the intermolecular GZ networks typically characterized by gels derived from pure GZ solutions.     

Chiral norbornadienes as efficient ligands for the rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to fumaric and maleic compounds

[reaction: see text] A rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to fumaric and maleic compounds has been developed. While phosphorus-based chiral ligands fail to induce high stereoselectivity, chiral norbornadiene ligands have proved to be uniquely effective to achieve high enantioselectivity in these 1,4-addition reactions.     

Characterization of preformed plasmas with an interferometer for ultra-short high-intensity laser-plasma interactions

The evolution of an Al preformed plasma produced by a prepulse was observed before and after the arrival of the main pulse by an interferometer using a femtosecond probe pulse. A central density depression due to the ponderomotive force of the main laser pulse in the preformed plasma with a 100 m scale length was clearly visible after the main pulse irradiation at an intensity of 5×10¹⁶ W/cm². The temporal profiles of the prepulse, characterized by a cross-correlation in conjunction with a precise density profile measurement by an interferometer, contribute to the better understanding of femtosecond laser-matter interactions. PACS 52.38.-r; 52.50.Jm; 52.70.-m     

Coherent manipulation of electronic States in a double quantum dot

We investigate coherent time evolution of charge states (pseudospin qubit) in a semiconductor double quantum dot. This fully tunable qubit is manipulated with a high-speed voltage pulse that controls the energy and decoherence of the system. Coherent oscillations of the qubit are observed for several combinations of many-body ground and excited states of the quantum dots. Possible decoherence mechanisms in the present device are also discussed.     

Electron localization and a confined electron gas in nanoporous inorganic electrides

The nanoporous main group oxide 12CaO.7Al(2)O3 (C12A7) can be transformed from a wide-gap insulator to an electride where electrons substitute anions in cages constituting a positive frame. Our ab initio calculations of the electronic structure of this novel material give a consistent explanation of its high conductivity and optical properties. They show that the electrons confined in the inert positive frame are localized in cages and undergo hopping between neighboring cages. The results are useful for the understanding of behavior of confined electron gas of different topology and electron-phonon coupling, and for designing new transparent conductors, electron emitters, and electrides.