Copper(II) complexes of a biphenyl-based ligand: Tuning the needs of the metal with those of the ligand

The novel pyrazole-containing tetradentate ligand 2,2′-bis[[(3,5-dimethylpyrazol-1-yl)methyl]amino]-1,1′-biphenyl (N₄-mpz), 1, was synthesized and three Cu(II) complexes, 2–4, were prepared from this compound. These complexes were characterized by a combination of elemental analysis, FAB-MS and electrochemistry and were shown to have the structure of [Cu(N₄-mpz)(Pz)]X₂ where X = BF₄ or ClO₄ or [Cu(N₄-mpz)(Cl)]Cl. The X-ray structure of [Cu(N₄-mpz)(Pz)] (ClO₄)₂ · CH₃OH, 2, was determined and it showed the Cu(II) coordinated by the four nitrogen donors from the ligand along with an exogenous pyrazole donor that had been extracted from another molecule of the ligand. Cyclic voltammetry studies indicated that the complexes undergo quasi-reversible one-electron reductions in acetonitrile at potentials between 396 and 422 mV versus Ag/AgCl.     

Empirical study of stochasticity for deterministic chaotical dynamics of geometric progressions of residues

Kolmogorov discovered in 1933 that the empirical statistics of several independent values of any random variable differs from the true distribution function of this variable in some universal way: the random distribution of the distance of one of these statistics from the other verifies (asymptotically) some stochastic distribution law (called later “Kolmogorov’s distribution”). The present paper compares the Kolmogorov’s distribution with a similar object, provided by the chain of observations of a nonrandom, deterministic dynamical system, formed by the consecutive members of a geometrical progression. Say, the Kolmogorov’s distribution is observed for the distribution of the last pairs of digits of the powers of integer 3, that is, for the sequence 01,03,09,27,81,43,29,87,… (which is not random at all and does not verify the Kolmogorov’s theorem conditions).     

低能电子在外层导电屏蔽的玻璃锥管中的传输

采用新的具有常数锥角的玻璃锥管,并对玻璃锥管进行了外表面导电屏蔽,通过对电子穿越玻璃锥管的二维角分布随时间演化的观测,研究了低能电子与玻璃管相互作用的机制.发现电子穿越完全放电的玻璃锥管时穿透率先下降后平稳,整个过程中角分布中心发生微小移动,但角分布的半高宽几乎保持不变.这与我们之前发表的工作(2016 Acta Phys.Sin.65 204103)不同,这是由于对玻璃锥管进行外表面导电屏蔽会阻止外界不确定的快速充放电的影响,并形成了新的稳定放电通道,有利于实现电子的稳定穿透.电子的穿透率随倾角呈类似矩形的分布,透射电子的角分布中心伴随倾角的变化而移动,其穿透所容许的倾角与几何穿透一致.     

Visualizing Acidophilic Microorganisms in Biofilm Communities Using Acid Stable Fluorescence Dyes

Bacteria in acidophilic biofilm communities, i.e. acid streamers and snottites, obtained from a subsurface mine in Königstein were visualized by fluorescence microscopy using four new fluorescent dyes (DY-601XL, V07-04118, V07-04146, DY-613). The pH of the bulk solution in which these bacteria thrive was pH 2.6 to 2.9. The new fluorescent dyes were all able to clearly stain and microscopically visualize in-situ the bacteria within the biofilm community without changing pH or background ion concentration. The commonly used fluorescent dyes DAPI and SYTO 59 were also applied for comparison. Both dyes, however, were not able to visualize any bacteria in-situ, since they were not stable under the very acid conditions. In addition, dye V07-04118 and dye DY-613 also possess the ability to stain larger cells which were presumably eukaryotic origin and may be attributed to yeast cells or amoeba-like cells. PCR analyses have shown that the dominant bacterial species in these acidophilic biofilm communities was a gram negative bacterium of the species Ferrovum myxofaciens. The presented four new dyes are ideal for in-situ investigations of microorganisms occurring in very acid conditions, e.g. in acidophilic biofilm communities when in parallel information on pH sensitive incorporated fluorescent heavy metals should be acquired.     

Dianionic Mononuclear Cyclo‐P4 Complexes of Zero‐Valent Molybdenum: Coordination of the Cyclo‐P4 Dianion in the Absence of Intramolecular Charge Transfer

Relative to other cyclic poly‐phosphorus species (that is, cyclo‐P_n), the planar cyclo‐P₄ group is unique in its requirement of two additional electrons to achieve aromaticity. These electrons are supplied from one or more metal centers. However, the degree of charge transfer is dependent on the nature of the metal fragment. Unique examples of dianionic mononuclear η⁴‐P₄ complexes are presented that can be viewed as the simple coordination of the [cyclo‐P₄]^2? dianion to a neutral metal fragment. Treatment of the neutral, molybdenum cyclo‐P₄ complexes Mo(η⁴‐P₄)I₂(CO)(CNAr^Dipp2)₂ and Mo(η⁴‐P₄)(CO)₂(CNAr^Dipp2)₂ with KC₈ produces the dianionic, three‐legged piano stool complexes, [Mo(η⁴‐P₄)(CO)(CNAr^Dipp2)₂]^2? and [Mo(η⁴‐P₄)(CO)₂(CNAr^Dipp2)]^2?, respectively. Structural, spectroscopic, and computational studies reveal a similarity to the classic η⁶‐benzene complex (η⁶‐C₆H₆)Mo(CO)₃ regarding the metal‐center valence state and electronic population of the planar‐cyclic ligand π system.     

Chemical Vapor Deposition of Phase‐Pure Uranium Dioxide Thin Films from Uranium(IV) Amidate Precursors

Homoleptic uranium(IV) amidate complexes have been synthesized and applied as single‐source molecular precursors for the chemical vapor deposition of UO₂ thin films. These precursors decompose by alkene elimination to give highly crystalline phase‐pure UO₂ films with an unusual branched heterostructure.     

Interactions of like-charged rods at low temperatures: Analytical theory vs. simulations

We investigate a system consisting of two like-charged infinitely long rods and neutralizing counterions at low temperatures, using both analytic theory and simulations. With some reasonable approximations we can analytically solve for several ground-state structures of the model, starting with states where all counterions are lined up in the gap between the rods, over planar configurations, where the counterions are divided up into a fraction which resides between the rods, and counterions which are located on the outer surfaces, up to configurations which cover the full rod surfaces. Using parallel tempering simulations, we are able to study the system over a wide range of temperatures. At low temperatures we find good agreement with our T = 0 results. At higher temperatures, the strong coupling (SC) theory delivers qualitatively better results. We furthermore demonstrate that for the SC theory and our ground-state approximations to yield quantitative agreement, three parameters are required to be large, the strong-coupling parameter Ξ, the Rouzina-Bloomfield parameter, and the ratio of the average distance of the counterions to the radius of the rods. In the case of the latter ratio being small, our T = 0 results show better agreement with the simulation data at very low temperatures.     

Dynamic pulsed-beam shaping using a TAG lens in the near UV

The ability to dynamically shape the spatial intensity profile of an incident laser beam enables new ways to modify and structure surfaces through pulsed laser processing. Here we describe a method to generate doughnut-shaped beams from an input Gaussian source using a tunable acoustic gradient index (TAG) lens. The TAG lens is capable of modulating between focused beams and annular rings of variable size, using sinusoidal driving frequencies. Laser micromachining is accomplished by synchronizing the TAG lens to a 355 nm pulsed nanosecond laser. Results in polyimide demonstrate the ability to generate adjacent surface features with different shapes and sizes.     

Influence of the substrate,metal overlayer and lattice neighbors on the focusing properties of colloidal microspheres

Calculations of the field distribution in colloidal SiO₂ microspheres are presented. Two cases are considered: small particles on a Si substrate irradiated by the 266 nm light, and larger ones, covered with a gold film and irradiated at 800 nm. Substrate, neighboring spheres and sputtered metal overlayer all significantly modify the field pattern and magnitude. Reflected light is focused inside the spheres, which may lead to their damage. The results can be useful in the analysis of microspheres-assisted nano-patterning.