Micellar effects on a ligand substitution reaction: Kinetics of the formation of [Fe(CN)5(μ‐pz)Ru(NH3)5]−, from [Fe(CN)5H2O]3− and [Ru(NH3)5pz]2+, in the presence of anionic micelles

The kinetics of substitution of H₂O by Ru(NH₃)₅pz²⁺ (pz = pyrazine) in Fe(CN)₅H₂O^3? have been studied in micellar aqueous solutions of sodium dodecylsulfate (SDS). Experimental results are discussed by using an approach based on the transition‐state theory. This approach is better than others based on the pseudophase model, which can also be used, because it is able to give a clear meaning to the parameters of the model. Trends in the observed reactivity are explained by a change in the degree of association of one of the reactants to the micelles (Ru(NH₃)₅pz²⁺ in the present work). This association is governed by an equilibrium constant that depends on the electrostatic potential at the surface of the micelles. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 627–633, 2004     

Supra­molecular assembly of (methanol)[10,15,20‐tris­(4‐cyano­phenyl)‐5‐(4‐pyridyl)­porphyrin­ato]­zinc(II) by inter­molecular hydrogen bonding and weak coordination

The crystal structure of the title compound, [Zn(C₄₆H₂₄N₈)(CH₄O)], consists of two‐dimensional supra­molecular arrays sustained by O—H⋯N(pyrid­yl) hydrogen bonding and weak Zn⋯NC coordination. The inter­layer organization in the crystal structure is characterized by tight stacking of the corrugated layers.     

Local and itinerant magnetism and superconductivity in R Rh2si2 (R = rare earth)

Magnetization and Mossbauer studies reveal that R Rh₂Si₂ (R = rare earth) have two magnetic phase transitions, one corresponding to the ordering of the rare earth (T^N = 27?130K) and the other to the itinerant electron ordering of the Rh sublattice (T^M= 5?17K). LaRh₂si₂ has also been studied by resistivity, specific heat and a.c. susceptibility measurements. All studies indicate that LaRh₂Si₂ orders magnetically at T^M= 7K and becomes superconducting, type II, at T^c= 3.8±0.2K.     

Properties of polyphenylene films deposited electrochemically in an HF-benzene system

Free-standing polyphenylene films, prepared by the electrochemical oxidation of benzene in an HF-benzene, two-phase system, were investigated. From electron microscope pictures, x-ray diffraction patterns, and infrared (IR) spectra of polyphenylene films and commercial polyphenylene powder it is concluded that the films, which are largely para linked, contain in addition a substantial amount of meta and possibly ortho linkages and are amorphous in nature. Doping with AsF₅ increases the electrical conductivity of the otherwise insulating films to 10^?4?10^?2ohm^?1cm^?1; doped films are relatively stable in air. The lower conductivity of doped films with respect to reported values for chemically synthesized poly-p-phenylene appears to be the result of the amorphous nature of the films.     

A New and Convenient Synthesis of Substituted Acylthioacylureas. Reaction of aryl and alkyl thioamides with acyl isocyanates

The addition of acyl isocyanates to a solution of aryl and alkyl thioamides affords substituted acylthioacylureas. The IR. spectra of substituted acylthioacylureas is described.     

Markov Chains with finite convergence time

We study the properties of finite ergodic Markov Chains whose transition probability matrix P is singular. The results establish bounds on the convergence time of P^m to a matrix where all the rows are equal to the stationary distribution of P. The results suggest a simple rule for identifying the singular matrices which do not have a finite convergence time. We next study finite convergence to the stationary distribution independent of the initial distribution. The results establish the connection between the convergence time and the order of the minimal polynomial of the transition probability matrix. A queuing problem and a maintenance Markovian decision problem which possess the property of rapid convergence are presented.     

Quark confinement in the two-dimensional lattice Higgs-Villain model

We prove quark confinement in the two-dimensional lattice Higgs-Villain model in the weak coupling region by using a Kirkwood-Salsburg equations for unbounded spins.Research partially supported by the National Science Foundation under Grant PHY-77-18762On leave from Department of Mathematics, University of British Columbia, Vancouver, B.C., Canada. Research partially supported by National Research Council under Grant A4015On leave from Istituto di Fisica Teorica, Napoli, Italy     

Diastereoisomerically selective enantiomerically pure titanium complexes of Salan ligands: synthesis, structure, and preliminary activity studies

The degree of diastereoselectivity in the wrapping of four new chiral Salan ligands to form chiral-at-metal titanium complexes ranged from mild to perfect as a function of the ligands' N substituents; the enantiomerically pure complexes catalyzed the addition of diethyl zinc to benzaldehyde in 73-76% enantiomeric excess.