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The para -N-pyridyl-based PCP pincer proligand 3,5-bis(di- tert -butylphosphinomethyl)-2,6-dimethylpyridine (pN- tBu PCP-H) was synthesized and metalated to give the iridium complex (pN- tBu PCP)IrHCl ( 2-H ). In marked contrast with its phenyl-based congeners, e.g., ( tBu PCP)IrHCl and derivatives, 2-H is highly air-sensitive and reacts with oxidants such as ferrocenium, trityl cation, and benzoquinone. These oxidations ultimately lead to intramolecular activation of a phosphino- t -butyl C(sp 3 )-H bond and cyclometalation. Considering the greater electronegativity of N than C, 2-H is expected to be less easily oxidized than simple PCP derivatives; cyclic voltammetry and DFT calculations support this expectation. However, 2-H is calculated to undergo metal-ligand-proton tautomerism (MLPT) to give an N-protonated complex that can be described with resonance forms representing a zwitterionic complex (with a negative charge on Ir) and a p -N-pyridylidene (a remote N-heterocyclic carbene) Ir(I) complex. One-electron oxidation of this tautomer is calculated to be dramatically more favorable than direct oxidation of 2-H (ΔΔ G ° = -31.3 kcal/mol). The resulting Ir(II) oxidation product is easily deprotonated to give metalloradical 2 • which is observed by NMR spectroscopy. 2 • can be further oxidized to give cationic Ir(III) complex , 2 + , which can oxidatively add a phosphino- t -butyl C-H bond and undergo deprotonation to give the observed cyclometalated product. DFT calculations indicate that less sterically hindered analogues of 2 + would preferentially undergo intermolecular addition of C(sp 3 )-H bonds, for example, of n -alkanes. The resulting iridium alkyl complexes could undergo facile β-H elimination to afford olefin, thereby completing a catalytic cycle for alkane dehydrogenation driven by one-electron oxidation and deprotonation, enabled by MLPT.

Background: Over the past decade, there has been a remarkable advancement in the understanding of autoimmune etiologies of encephalitis. The first identified generation of paraneoplastic encephalitis tends to occur in older populations, responds poorly to immunotherapy, and is mediated by T-cell damage with antibodies directed toward intracellular antigens. A new generation of autoimmune encephalitides has been described, which are mediated by antibodies to cell-surface proteins, tend to occur in younger individuals, are less frequently associated with malignancy, and often respond better to treatment compared to their intracellular antigen-related paraneoplastic counterparts. This review will focus on several specific antibody-mediated autoimmune encephalitides with neuro-ophthalmic pertinence., Evidence Acquisition: Literature review and personal clinical experience., Results: Several of the antibody-mediated encephalitides, specifically N-methyl-D-aspartate receptor, dipeptidyl-peptidase-like protein 6, glial fibrillary acidic protein, metabotropic glutamate receptor 1 (mGluR1), gamma-aminobutyric acid receptor, glutamic acid decarboxylase 65 (GAD65), collapsing response mediator protein 5 (CRMP5), and kelch-like protein 11 (KLHL11), contain features of neuro-ophthalmic interest., Conclusions: The novel cell-surface protein-directed autoimmune encephalitis group can present with a wide range of afferent and efferent neuro-ophthalmic manifestations. Neuro-ophthalmologists should be familiar with these antibody-associated syndromes, which are treatable and often require a high index of suspicion for diagnosis.

The alkyl group is the most common component of organic molecules and the most difficult to selectively functionalize. The development of catalysts for dehydrogenation of alkyl groups to give the corresponding olefins could open almost unlimited avenues to functionalization. Homogeneous systems, or more generally systems based on molecular (including solid-supported) catalysts, probably offer the greatest potential for regio- and chemoselective dehydrogenation of alkyl groups and alkanes. The greatest progress to date in this area has been achieved with pincer-ligated transition-metal-based catalysts; this and related chemistry are the subject of this review. Chemists are still far from achieving the most obvious and perhaps most attractive goal in this area, the dehydrogenation of simple alkanes to yield alkenes (specifically monoenes) with high yield and selectivity. Greater progress has been made with tandem catalysis and related approaches in which the initial dehydrogenated product undergoes a desirable secondary reaction. Also reviewed is the substantial progress that has been made in the closely related area of dehydrogenation of alkyl groups of substrates containing heteroatoms.

Various biological methods are being recognized for the fabrication of silver nanoparticles, which are used in several fields. The phytosynthesis of nanoparticles came out as a cost effective and enviro-friendly approach. When root bark extract of Berberis lycium was treated with silver ions, they reduced to silver nanoparticles, which were spherical, crystalline, size ranged from 10-100nm and capped by biomolecules. Synthesized silver nanoparticles were characterized by UV-visible spectroscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD) and Fourier Transform Infra Red Spectroscopy (FTIR). The plant mediated synthesized silver nanoparticles showed pronounced antimicrobial activities against both Gram negative bacteria (Escherichia coli, Klebseilla pneumoniae, Pseudomonas aeruginosa) and Gram positive bacteria (Staphylococcus aureus and Bacillus subtilis). The plant mediated process proved to be non-toxic and low cost contender as reducing agent for synthesizing stable silver nanoparticles.

The purpose of this study was to assess the weathering of finely ground phlogopite, a trioctahedral mica, by placing it in contact with heterotrophic (Bacillus cereus) and acidophilic (Acidithiobacillus ferrooxidans) cultures. X-ray diffraction analyses of the phlogopite sample before and after 24 weeks of contact in B. cereus cultures revealed a decrease in the characteristic peak intensities of phlogopite, indicating destruction of individual structural planes of the mica. No new solid phase products or interlayer structures were detected in B. cereus cultures. Acidithiobacillus ferrooxidans cultures enhanced the chemical dissolution of the mineral and formed partially weathered interlayer structures, where interlayer K was expelled and coupled with the precipitation of K-jarosite [KFe3(SO4)2(OH)6].

The purpose of this work was to determine solution- and solid-phase changes associated with the oxidative leaching of arsenopyrite (FeAsS) by Thiobacillus ferrooxidans and a moderately thermoacidophilic mixed culture. Jarosite [KFe(3)(SO(4))(2)(OH)(6)], elemental sulfur (S), and amorphous ferric arsenate were detected by X-ray diffraction as solid-phase products. The oxidation was not a strongly acid-producing reaction and was accompanied by a relatively low redox level. The X-ray diffraction lines of jarosite increased considerably when ferrous sulfate was used as an additional substrate for T. ferroxidans. A moderately thermoacidophilic mixed culture oxidized arsenopyrite faster at 45 degrees C than did T. ferroxidans at 22 degrees C, and the oxidation was accompanied by a nearly stoichiometric release of Fe and As. The redox potential was initially low but subsequently increased during arsenopyrite oxidation by the thermoacidophiles. Jarosite, S, and amorphous ferric arsenate were also formed under these conditions.

The biological leaching of pyrrhotite (Fe(1-x)S) by Thiobacillus ferrooxidans was studied to characterize the oxidation process and to identify the mineral weathering products. The process was biphasic in that an initial phase of acid consumption and decrease in redox potential was followed by an acid-producing phase and an increase in redox potential. Elemental S was one of the first products of pyrrhotite degradation detected by X-ray diffraction. Pyrrhotite oxidation also yielded K-jarosite [KFe(3)(SO(4))(2)(OH)(6)], goethite (alpha-FeOOH), and schwertmannite [Fe(8)O(8)(OH)(6)SO(4)] as solid-phase products. Pyrrhotite was mostly depleted after 14 days, whereas impurities in the form of pyrite (cubic FeS(2)) and marcasite (orthorhombic FeS(2)) accumulated in the leach residue.

A simple apparatus for measuring hardness of Gelrite and agar plates, that can be easily fabricated, is described. It gives reproducible results comparable with those obtained with expensive commercial equipment. It has been successfully used to improve enumeration ofThiobacillus ferrooxidans andT. thiooxidans on solid media plates.