Synthesis and Characterization of Symmetrical -Heterocyclic Carbene Copper(II) Complexes-An Investigation of the Influence of Pyridinyl Substituents.

Three new tridentate copper(II) -heterocyclic carbene (NHC) complexes have been obtained and characterized with symmetrical C-4 substitutions on their pendent pyridine rings. Substitutions including methyl (Me), methoxy (OMe), and chloro (Cl) groups, which extend the library pincer Cu-NHC complexes under investigation, modify the impact of pyridinyl basicity on NCN pincer complexes. Both ligand precursors and copper(II) complexes are characterized using a range of techniques, including nuclear magnetic resonance (NMR) spectroscopy for H, C, P, and F nuclei, electrospray ionization mass spectrometry (ESI-MS), X-ray crystallography, cyclic voltammetry, and UV-Vis spectroscopy.

Aminoquinoline-Based Tridentate ()-Copper Catalyst for C-N Bond-Forming Reactions from Aniline and Diazo Compounds.

A new tridentate Cu complex based on ()-1-(pyridin-2-yl)--(quinolin-8-yl)methanimine (PQM) was generated and characterized to support the activation of diazo compounds for the formation of new C-N bonds. This neutral Schiff base ligand was structurally characterized to coordinate with copper(II) in an equatorial fashion, yielding a distorted octahedral complex. Upon characterization, this copper(II) complex was used to catalyze an efficient and cost-effective protocol for C-N bond formation between -nucleophiles and copper carbene complexes arising from the activation of diazo carbonyl compounds.

Three water-soluble copper(II) -heterocyclic carbene complexes: toward copper-catalyzed ketone reduction under sustainable conditions.

A series of tridentate copper(II) -heterocyclic carbene (NHC) complexes with imidazole, benzimidazole, and 5,6-dimethylbenzimidazole azole rings were synthesized and comprehensively characterized X-ray crystallography, ESI-MS, cyclic voltammetry, and UV-Vis and EPR spectroscopic studies. These complexes were then utilized for the optimization of ketone reduction under sustainable conditions using 2-acetylpyridine and phenylsilane. The relationships between product formation, temperature, reaction time, and catalyst loading for the hydrogenation reactions are covered in detail.

Inosine 5'- monophosphate derived umami taste intensity of beef determination by electrochemistry and chromatography.

The umami sensation contributes to beef taste and acceptability. Inosine 5'- monophosphate (IMP), the most abundant 5'-ribonucleotide in meat, is known to impart an umami taste without the undesired side effects commonly associated with glutamate. Nevertheless, the investigation of IMP's role in beef flavor has thus far been overlooked.

Copper(II) NHC Catalyst for the Formation of Phenol from Arylboronic Acid.

Arylboronic acids are commonly used in modern organic chemistry to form new C-C and C-heteroatom bonds. These activated organic synthons show reactivity with heteroatoms in a range of substrates under ambient oxidative conditions. This broad reactivity has limited their use in protic, renewable solvents like water, ethanol, and methanol.

Tuning the copper(II)/copper(I) redox potential for more robust copper-catalyzed C-N bond forming reactions.

Complexes of copper and 1,10-phenanthroline have been utilized for organic transformations over the last 50 years. In many cases these systems are impacted by reaction conditions and perform best under an inert atmosphere. Here we explore the role the 1,10-phenanthroline ligand plays on the electronic structure and redox properties of copper coordination complexes, and what benefit related ligands may provide to enhance copper-based coupling reactions.

Modifying Current Collectors to Produce High Volumetric Energy Density and Power Density Storage Devices.

We develop zirconium-templated NiO/NiOOH nanosheets on nickel foam and polypyrrole-embedded in exfoliated carbon fiber cloth as complementary electrodes for an asymmetric battery-type supercapacitor device. We achieve high volumetric energy and power density by the modification of commercially available current collectors (CCs). The modified CCs provide the source of active material, actively participate in the charge storage process, provide a larger surface area for active material loading, need no additional binders or conductive additives, and retain the ability to act as the CC.

Iron Oxide Nanosheets and Pulse-Electrodeposited Ni-Co-S Nanoflake Arrays for High-Performance Charge Storage.

Nanostructured nickel cobalt sulfide (NiCoS) has been prepared through a single-step pulse-electrodeposition method. Iron oxide nanosheets at hollow graphite shells (FeO@g-shells) were prepared from graphite-coated iron carbide/α-Fe (g-FeC/Fe) in a two-step annealing/electrochemical cycling process. Electrochemical characterization of the NiCoS and g-FeC/Fe materials showed that both have high specific capacities (206 mAh g and 147 mAh g at 1 A g) and excellent rate capabilities (∼95% and ∼83% retention at 20 A g, respectively).

Solution pH change in non-uniform alternating current electric fields at frequencies above the electrode charging frequency.

AC Faradaic reactions have been reported as a mechanism inducing non-ideal phenomena such as flow reversal and cell deformation in electrokinetic microfluidic systems. Prior published work described experiments in parallel electrode arrays below the electrode charging frequency (fc ), the frequency for electrical double layer charging at the electrode. However, 2D spatially non-uniform AC electric fields are required for applications such as in plane AC electroosmosis, AC electrothermal pumps, and dielectrophoresis.

Spatially variant red blood cell crenation in alternating current non-uniform fields.

Alternating-current (AC) electrokinetics involve the movement and behaviors of particles or cells. Many applications, including dielectrophoretic manipulations, are dependent upon charge interactions between the cell or particle and the surrounding medium. Medium concentrations are traditionally treated as spatially uniform in both theoretical models and experiments.

Imaging of metal ion dissolution and electrodeposition by anodic stripping voltammetry-scanning electrochemical microscopy.

We have developed a new imaging method for scanning electrochemical microscopy (SECM) employing fast-scan anodic stripping voltammetry (ASV) to provide sensitive and selective imaging of multiple chemical species at interfaces immersed in solution. A rapid cyclic voltammetry scan (100 V/s) is used along with a short preconcentration time (300-750 ms) to allow images to be acquired in a normal SECM time frame. A Hg-Pt film electrode is developed having an equivalent Hg thickness of 40 nm that has good sensitivity at short preconcentration times and also retains thin-film behavior with high-speed voltammetric stripping.

In situ electrochemical STM study of the coarsening of platinum islands at double-layer potentials.

In situ electrochemical scanning tunneling microscopy is used to study the coarsening of platinum islands at potentials of 0.4, 0.5, and 0.

Feedback effects in combined fast-scan cyclic voltammetry-scanning electrochemical microscopy.

Fast-scan cyclic voltammetry at scan rates between 5 and 1000 V s(-1) was performed at the tip of a scanning electrochemical microscope immersed in a solution of redox mediator. The effect of conducting and insulating substrates on the voltammetric signal was investigated as a function of scan rate and tip-substrate distance. It was found that diffusional interactions between the tip and the substrate are greatest at lower scan rates and on the reverse sweep of the voltammogram.

Scanning electrochemical microscopy of model neurons: constant distance imaging.

Undifferentiated and differentiated PC12 cells were imaged with the constant-distance mode of scanning electrochemical microscopy (SECM) using carbon ring and carbon fiber tips. Two types of feedback signals were used for distance control: the electrolysis current of a mediator (constant-current mode) and the impedance measured by the SECM tip (constant-impedance mode). The highest resolution was achieved using carbon ring electrodes with the constant-current mode.

Scanning electrochemical microscopy of model neurons: imaging and real-time detection of morphological changes.

Living PC12 cells, a model cell type for studying neuronal function, were imaged using the negative feedback mode of a scanning electrochemical microscope (SECM). Six biocompatible redox mediators were successfully identified from a large pool of candidates and were then used for imaging PC12 cells before and after exposure to nerve growth factor (NGF). When exposed to NGF, cells differentiate into a neuron phenotype by growing narrow neurites (1-2 microm wide) that can extend > 100 microm from the cell proper.