Electronic effects on the rates of coupled two-electron/halide self-exchange reactions of substituted ruthenocenes

The complexes (MemCp)(MenCp)Ru (m,n = 1,1; 0.4; 0.5; 1.5) have been synthesized along with the corresponding halometalloceniums [(MemCp)(MenCp)RuX]+ (X = Cl, Br, I). The two-electron/halide transfer self-exchange kinetics have been determined and compared to those of the Cp2Ru/[Cp2RuX]+ parent system. Methylation decreases the rate of exchange monotonically, and plots of ln(kex) vs number of methyl groups are linear for constant X. It is concluded that steric effects do not contribute significantly to the observed kinetics. Thermodynamic studies of halide substitution equilibria support the conclusion that the electronic effects of methylation are essentially additive.     

Electrical transport in rings of single-wall nanotubes: one-dimensional localization

We report low-temperature magnetoresistance (MR) measurements on rings of single-wall carbon nanotubes. Negative MR characteristic of weak one-dimensional localization is clearly observed from 3.0 to 60 K, and the coherence length L(varphi) is obtained as a function of temperature. The dominant dephasing mechanism is identified as electron-electron scattering. Below 1 K, we observe a transition from weak to strong localization, and below 0.7 K a weak antilocalization is induced by spin-orbit scattering.     

Thermal rearrangement of dienolesters. Sequential [1.3] sigmatropic rearrangement and intramolecular diels-alder cycloaddition of 1-methylene-2-methyl-2-propenyl hex-5-enoate

The high temperature thermal rearrangement of the title dienol ester is reported. Its reactions entail a [1.3] acyl shift followed by intramolecular Diels-Alder cyclo-addition of the resulting β-diketone.     

Simple and Sensitive Electrochemical DNA Detection of Primer Generation‐Rolling Circle Amplification

A new electrochemical sequence‐specific DNA detection platform based on primer generation‐rolling circle amplification (PG‐RCA), methylene blue (MB) redox indicator, and indium tin oxide (ITO) electrode is reported. In the presence of a specific target sequence, PG‐RCA, an isothermal DNA amplification technique, produced large amounts of amplicons in an exponential manner. In addition to the standard components, the reaction mixture contained MB, which bound with the PG‐RCA amplicons. End‐point electrochemical measurement by differential pulse voltammetry (DPV) was performed using ITO electrode. The amplicon‐bound MB resulted in a lower DPV signal than free MB due to a smaller diffusion coefficient as well as electrostatic repulsion between the negatively charged amplicon‐bound MB and ITO electrode. With simple assay design (recognition probe) and instrumentation (operating temperature at 37 °C and ITO electrode without the need for probe immobilization), this detection platform is well suited for point‐of‐care and on‐site testing. Real‐time measurement was also achieved by pretreating the ITO electrode with bovine serum albumin.     

Low-Rank Matrix Recovery with Composite Optimization: Good Conditioning and Rapid Convergence

Foundations of Computational Mathematics - The task of recovering a low-rank matrix from its noisy linear measurements plays a central role in computational science. Smooth formulations of the...     

Phase transfer catalysts anchored to polystyrene

Quarternary phosphonium and ammonium salts attached to polystyrene resins by short (2 - 3 atom) carbon chains are highly active phase transfer catalysts for a variety of nucleophilic substitution reactions.