Metallic macrocycle with a 1,3-alternate calix[4]arene phosphorus ligand

The preparation of an 1,3-alternate calix[4]arene phosphorus ligand, 25,27-bis(2-(diphenylphosphino)ethoxy)-26,28-bis(1-propyloxy)calix[4]arene (3), is presented. Ligand 3 is obtained in three steps in 64% overall yield. Reaction of 3 with [Rh(cot)2]BF4 produced the encapsulated rhodium complex [Rh[(P,P)-diphen-calix[4]arene]]BF4 (4). As revealed by a single-crystal X-ray diffraction study, the rhodium center has a bent coordination environment with a P-Rh-P angle of 135.66(3) degrees. Palladation of 3 employing [Pd(MeCN)4](BF4)2 yielded the chelate palladium complex 7 in which the palladium center has a slightly bent configuration. Treatment of the ligand with Pd(cod)Cl2 and [Pd(eta3-C4H7)(THF)2]BF4 leads to the isolation of the monometallic complex. Full characterization includes X-ray structural studies of compounds 3, 4, and 6.     

Light absorption by free semiconductor carriers in the presence of a laser wave

Within the framework of the conditions ; » ^–1 ( ^–1 is the mean time of momentum relaxation), the coefficient of absorption () of a weak electromagnetic wave by the free carriers of a polar semiconductor is calculated in the presence of a strong wave (of frequency ), for arbitrary values of and . Photon absorption by band electrons is due to these latter interacting with optical phonons (of frequency _o). The problem is solved by using an analogous approach to the theory of the linear Kubo reaction. The results are valid in the absence of electron heating, when a strong wave only influences the scattering probability. The appearance of a photostimulated tail of absorption is predicted for < _o, including the jump () for ( – _o + ) ₀T as well as peaks in the function () at the points _s=s (s=1, 2, 3,...). The value (₁) is determined by the formula for the absorption coefficient for one strong wave.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 105–109, July, 1981.The authors are grateful to É. M. Épshtein and Sh. M. Kogan for useful discussions.     

Aqueous synthesis of alkanethiolate-protected Ag nanoparticles using Bunte salts

The one-pot synthesis of monolayer-protected metal nanoparticles derived from sodium S-dodecylthiosulfate (Bunte salt) in aqueous solution is described. Silver nanoparticles, which were produced by the borohydride reduction of silver nitrate in H2O, were stabilized by the adsorption of S-dodecylthiosulfate followed by the removal of the SO3- moiety. Temporary stabilization of silver sols by the adsorption of borohydride and borate prevented aggregation of silver nanoparticles in H2O. The syntheses of other metal nanoparticles, including gold, copper, and palladium particles in H2O, were less successful. Gold and copper particles were completely aggregated and precipitated out immediately after the addition of NaBH4, yielding only insoluble clusters. Stable and soluble palladium nanoparticle could be prepared, but the presence of Pd-thiolate complex was also observed. These nanoparticles were characterized using 1H NMR, UV-vis spectroscopy, FT-IR spectroscopy, and transmission electron microscopy.     

Optically induced level anticrossing in undoped GaAs/AlGaAs coupled double quantum wells

We report a photoluminescence detected anticrossing of the energy levels in an undoped asymmetric coupled-double-quantum-well buried in a p-i-n structure. Due to the built-in electric field, the quantum wells are tilted in such a way that the symmetric energy level is higher than that of the antisymmetric one in the conduction band. Keeping the laser excitation energy below the barrier, with increasing laser power, the level anticrossing and the quantum confined Stark effect were observed due to decreasing built-in electric field by the photogenerated electron and hole pairs.     

Multiferroic characteristics of the strained epitaxial Bi0.9Ho0.1FeO3 thin film

We fabricated high quality epitaxial Bi_0.9Ho_0.1FeO₃ thin films which exhibited the tetragonally stained structure with a c/a ratio of about 1.04. The Bi_0.9Ho_0.1FeO₃ thin film showed a good ferroelectric property with the high remanent polarization (P_r) of about 80 μC/cm². The ferromagnetic hysteresis loop with a clear remanent magnetization was shown. The coercive field and the remanent magnetization of the Bi_0.9Ho_0.1FeO₃ film are 6200 Oe and 1.7 emu/g, respectively. The abrupt conduction due to space charge limited (SCL) was revealed in leakage current density versus electric field.     

Properties of differences of meromorphic functions

Let f be a transcendental meromorphic function. We propose a number of results concerning zeros and fixed points of the difference g(z) = f(z + c) − f(z) and the divided difference g(z)/f(z).     

New methods for calculating the dew/bubble curves of classical model fluids

We describe two new methods for locating the dew/bubble curves of fluids. One is a numerical method and the other an analytical method based on the use of series expansions. The utility of these two methods is illustrated by application to a simple one-component fluid model and to several model polydisperse fluids. The numerical method is based on a new geometric representation of the equilibrium conditions-similar in spirit to the geometric representations often used for solving the equilibrium conditions of pure fluids. Our calculations show that the series-expansion technique can be quite effective at producing accurate representations of the phase boundaries.