Functional Hydride Transfer by a Thiolate‐Containing Model of Mono‐Iron Hydrogenase featuring an Anthracene Scaffold

We report the synthesis, X‐ray structure and functional biomimetic activity of a model complex of mono‐iron hydrogenase (Hmd). To achieve the desired biomimetic fac‐CNS(thiolate) ligation motif, an anthracene framework is used to provide the requisite donors in a single chelate. A bulky aryl thiolate (ortho dimethylphenyl) is included to achieve mononuclearity. In addition to exhibiting structural (X‐ray) and spectroscopic (NMR, IR) similarity to the enzyme, the complex is competent for H₂ activation (heterolysis) and hydride transfer to a model substrate—mimicking the functional behavior of the enzyme in a biomimetic CNS coordination sphere for the first time.     

Terminal Hydride Species in [FeFe]‐Hydrogenases Are Vibrationally Coupled to the Active Site Environment

A combination of nuclear resonance vibrational spectroscopy (NRVS), FTIR spectroscopy, and DFT calculations was used to observe and characterize Fe?H/D bending modes in CrHydA1 [FeFe]‐hydrogenase Cys‐to‐Ser variant C169S. Mutagenesis of cysteine to serine at position 169 changes the functional group adjacent to the H‐cluster from a ‐SH to ‐OH, thus altering the proton transfer pathway. The catalytic activity of C169S is significantly reduced compared to that of native CrHydA1, presumably owing to less efficient proton transfer to the H‐cluster. This mutation enabled effective capture of a hydride/deuteride intermediate and facilitated direct detection of the Fe?H/D normal modes. We observed a significant shift to higher frequency in an Fe?H bending mode of the C169S variant, as compared to previous findings with reconstituted native and oxadithiolate (ODT)‐substituted CrHydA1. On the basis of DFT calculations, we propose that this shift is caused by the stronger interaction of the ‐OH group of C169S with the bridgehead ‐NH‐ moiety of the active site, as compared to that of the ‐SH group of C169 in the native enzyme.     

Improvements in the electrochemical generation of arsine at gold electrodes as a sample introduction strategy for arsenic determination in well-water samples by atomic absorption spectrometry

The development and evaluation of a cathode consisting of a gold electrode covered by a polyaniline film, PANI/Au modified electrode, for electrochemical generation of arsine is described. The efficiency of arsine production using the new electrode was ascertained by comparison with corresponding hydride generation atomic absorption spectroscopy determinations of arsenic (As) in aqueous standards. The PANI/Au modified electrodes provide better sensitivity, accuracy and precision than the pure Au cathodes. The PANI/Au cathodes were prepared by controlled electrodeposition cycles of polyaniline films on top of Au electrodes. Cathodes obtained after 10 electrodeposition cycles showed the best performance, while the ones obtained after five voltammetry cycles produced films too thin and those obtained after 20 voltammetry cycles produced films too thick for the purpose of this work. Under optimised conditions, the As limit of detection in aqueous solutions, according to the (3σ) criterion, was 2.48 µg L^?1. For accuracy determination, the modified electrode was applied to quantification of As(III) in acidified aqueous solutions of the certified standard reference material, NIST SRM 1643d, and in well-water samples containing possible interfering ions. Application of the Student’s t-test showed no significant difference between the expected and obtained results of the NIST SRM standard analysis at the 95% confidence level. Values for six replicate determinations of As(III) in the well-water samples showed close agreement with values obtained by analyses using hydride generation atomic absorption. Recoveries were in the range of 95–105% at test for acceptable accuracy in the analysis of real samples.     

氢化物发生-原子荧光光谱法测定白酒中的痕量铅

建立氢化物发生-原子荧光光度法测定白酒中痕量铅的方法.对测定铅的影响因素进行分析和研究,优化了仪器的最佳工作参数,确定了最适宜的分析条件.铅标准溶液浓度在0～20.0μg/L范围内,标准曲线具有良好的线性,铅的检出限为1μg/L,回收率为94.0%～108.0%,相对标准偏差为3.28%～4.03%(n=11).     

A simple and convenient method for the synthesis of cyclobutenediones from alkynes using new Fe(CO)5/NaH/MeI reagent system

Iron carbonyl complexes prepared in situ using the Fe(CO)₅/NaH/MeI reagent combination and alkynes at 25 °C give the corresponding cyclobutenediones in 50-65% yields after CuCl₂ · 2H₂O oxidation.     

碱熔-氢化物发生原子荧光光谱法连续测定锑精矿中的砷、铋、硒、锡

建立了氢化物发生原子荧光光谱法测定锑精矿中砷、铋、硒、锡的方法.研究了基体及共存元素的干扰情况,实验表明,在酒石酸、硫脲-抗坏血酸存在下,适当的增加酸度可以有效地消除干扰.采用Na2O2熔解样品,用HCl酸化,无需分离基体,实现了锑精矿中砷、铋、硒、锡的连续测定,其回收率为90.6%～103.8%,检出限分别为0.35、0.20、0.65和0.35 μg/L.应用该方法分析了锑精矿样品,结果令人满意.     

氢化物发生-银盐分光光度法测定中草药中砷的含量

采用氢化物发生-银盐分光光度法对中草药中溶解态砷的含量进行了测定。结果表明,砷标准曲线的回归方程为C=1．4474 A-0．0087,r=0．99,在0～0．4μg/mL的范围内,线性关系良好。对5种样品进行了回收实验,回收率为92．4％-102．6％,相对标准偏差为1．26％-2．43％。该法简单、快速、灵敏、准确。     

Activation of Dihydrogen by Masked Doubly Bonded Aluminum Species

Activation of dihydrogen by masked dialumenes (Al=Al doubly bonded species) is reported. Reactions of barrelene‐type dialumanes, which have the reactivity as masked equivalents of 1,2‐diaryldialumenes ArAl=AlAr, with H₂ afforded dihydroalumanes ArAlH₂ at room temperature (Ar: bulky aryl groups). These dihydroalumanes form hydrogen‐bridged dimers [ArHAl(μ‐H)]₂ in the crystalline state, while a monomer–dimer equilibrium was suggested in solution. The 1,2‐diaryldialumenes generated from the barrelene‐type dialumanes are the putative active species in the cleavage of H₂.     

Rapid Photoactivated Generation of Nitroxyl (HNO) under Neutral pH Conditions

Directly obtaining kinetic and mechanistic data for the reactions of nitroxyl (HNO) with biomolecules (k≈10³–10⁷ m ^?1 s^?1) is not feasible for many systems because of slow HNO release from HNO donor molecules (t_1/2 is typically minutes to hours). To address this limitation, we have developed a photoactivatable HNO donor incorporating the (3‐hydroxy‐2‐naphthalenyl)methyl phototrigger, which rapidly releases HNO on demand. A “proof of concept” study is reported, which demonstrates that, upon continuous xenon light excitation, rapid decomposition of the HNO donor occurs within seconds. The amount of HNO generated is strongly dependent on solvent and the rate of the reaction is dependent on the light intensity.