Synthesis and characterization of a series of N3O-ligated mononuclear Mn(II) halide complexes

Treatment of a N₃O-donor chelate ligand (mpppa = N-methyl-N-((6-pivaloylamido-2-pyridyl)methyl)-N-(2-pyridylethyl)amine; bpppa = N-benzyl-N-((6-pivaloylamido-2-pyridyl)methyl)-N-(2-pyridylmethyl)amine) with equimolar amounts of Mn(ClO₄)₂ · 6H₂O and Me₄NX (X = Cl, Br, I) in methanol resulted in the production of a series of mononuclear Mn(II) halide complexes of the formula [(L)Mn-X(CH₃OH)]ClO₄ (L = mpppa or bpppa). X-ray crystallographic studies of [(mpppa)Mn-Cl(CH₃OH)]ClO₄ · CH₃OH (2 · CH₃OH), [(mpppa)Mn-Br(CH₃OH)]ClO₄ · CH₃OH (4 · CH₃OH), [(mpppa)Mn-I(CH₃OH)]ClO₄ · CH₃OH (6 · CH₃OH), and [(bpppa)Mn-I(CH₃OH)]ClO₄ · O₂(CH₂CH₃)₂ (7 · O(CH₂CH₃)₂) revealed for each a mononuclear Mn(II) center having tetradentate coordination of the chelate ligand, one coordinated halide anion, and one molecule of coordinated methanol. An increase in the Mn-X distance through the halide series (Cl, Br, I) correlates linearly with the increase in the radius of the anion. The magnetic moment of each halide complex, measured via Evans method in methanol, is consistent with the presence of a high-spin distorted octahedral Mn(II) center. The EPR features of the halide complexes in methanol do not change as a function of the nature of the halide coordinated to the Mn(II) center.     

施用甲醇刺激矮牵牛的生长效应与其代谢关系初探

大量研究表明施用甲醇能够促进多种植物的生长,在甲醇刺激植物生长的机理中,支持碳源假说的证据最多。该研究通过考察矮牵牛甲醇代谢与甲醇刺激其生长的相关性,对碳源假说进行验证。结果表明:(1)在MS固体培养基上添加2和6mmol/L CH3OH均可促进矮牵牛的生长和叶绿素含量增加,但2mmol/L CH3OH(低浓度)效果好于6mmol/L(高浓度),而且添加6mmol/L CH3OH会诱发较强的氧化胁迫。(2)进一步用13 C-NMR分析矮牵牛对不同浓度13 CH3OH的代谢作用发现,6mmol/L 13 CH3OH处理矮牵牛中[U-13 C]Fruc和[U-13 C]Gluc的生成量显著大于2mmol/L 13 CH3OH处理,即来自甲醇的碳源在代谢过程中虽被卡尔文循环同化为糖类物质,但这部分碳源对甲醇刺激矮牵牛的生长贡献不大。这些证据表明CH3OH代谢与其刺激矮牵牛生长的效果没有关联性,该实验结果不支持碳源假说。     

A theoretical study on the hydrogen-bonding interactions between flavonoids and ethanol/water

Ethanol and water are the solvents most commonly used to extract flavonoids from propolis. Do hydrogen-bonding interactions exist between flavonoids and ethanol/water? In this work, this question was addressed by using density functional theory (DFT) to provide information on the hydrogen-bonding interactions between flavonoids and ethanol/water. Chrysin and Galangin were chosen as the representative flavonoids. The investigated complexes included chrysin–H₂O, chrysin–CH₃CH₂OH, galangin–H₂O and galangin–CH₃CH₂OH dyads. Molecular geometries, hydrogen-bond binding energies, charges of monomers and dyads, and topological analysis were studied at the B3LYP/M062X level of theory with the 6?31++G(d,p) basis set. The main conclusions were: (1) nine and ten optimized hydrogen-bond geometries were obtained for chrysin–H₂O/CH₃CH₂OH and galangin–H₂O/CH₃CH₂OH complexes, respectively. (2) The hydrogen atoms except aromatic H1 and H5 and all of the oxygen atoms can form hydrogen-bonds with H₂O and CH₃CH₂OH. Ethanol and water form strong hydrogen-bonds with the hydroxyl, carbonyl and ether groups in chrysin/galangin and form weak hydrogen-bonds with aromatic hydrogen atoms. Except in structures labeled A and B, chrysin and galangin interact more strongly with H₂O than CH₃CH₂OH. (3) When chrysin and galangin form hydrogen-bonds with H₂O and CH₃CH₂OH, charge transfers from the hydrogen-bond acceptor (H₂O and CH₃CH₂OH in structures A, B, G, H, I, J) to the hydrogen-bond donor (chrysin and galangin in structure A, B, G, H, I, J). The stronger hydrogen-bond makes the hydrogen-bond donor lose more charge (A> B> G> H> I> J). (4) Most of the hydrogen-bonds in chrysin/galangin?H₂O/CH₃CH₂OH complexes may be considered as electrostatic dominant, while C?O2···H in structures labeled E and C?O5···H in structures labeled J are hydrogen-bonds combined of electrostatic and covalent characters. H9, H7, and O4 are the preferred hydrogen-bonding sites.     

Complete dechlorination of tetrachloroethene to ethene in presence of methanogenesis and acetogenesis by an anaerobic sediment microcosm

An anaerobic consortium taken from brackish sediments, enriched byPCE/CH₃OH sequential feeding, was capable of completely dechlorinating tetrachloroethene(PCE) to ethene (ETH). In batch experiments, PCE (0.5 mM) was dechlorinated to ethene (ETH) in approximately 75 h with either CH₃OH or H₂ as the electron donor. When VC (0.5 mM) was added instead of PCE it was dechlorinated without any initial lag by the PCE/CH₃OHenriched consortium, although at a lower dechlorination rate. In batch tests H₂ could readilyreplace CH₃OH for supporting PCE dechlorination, with a similar PCE dechlorination rate andproduct distribution with respect to those observed with methanol. This indicates that H₂ productionduring CH₃OH fermentation was not the rate-limiting step of PCE or VC dechlorination.Acetogenesis was the predominant activity when methanol was present. A remarkable homoacetogenicactivity was also observed when hydrogen was supplied instead of methanol.     

Effects of Photosystem II extrinsic proteins on microstructure of the oxygen-evolving complex and its reactivity to water analogs

We used Triton-prepared PS II membranes in studies of the inactivation of O₂ evolution and solubilization of Mn and specific PS II polypeptides by NH₂OH, N- and O-substituted NH₂OH derivatives, NH₂NH₂ and NH₄Cl. The inactivation of O₂-evolution, solubilization of Mn and the solubilization of the extrinsic PS II polypeptides (17, 23 and 33 kDa) proved closely correlated, half-maximal effects occurring with only 100 μM NH₂OH. NH₂OH (2 mM) and NaCl (1 M) extractions solubilized about one-half the amount of protein solubilized by 0.8 M Tris-HCl (pH 8.0). The inactivation of the Mn-S-state complex proceeded by apparent first-order kinetics, the rate constant dependent on NH₂OH (CH₃NHON) concentration and pH. In the range of micromolar concentrations of NH₂OH, this inactivation did not occur via a cooperative type mechanism. Depletion of the 17 and 23 kDa proteins modified the pH dependency of inactivation (from pH 7.8 to 6.5) and also resulted in an approx. 2-fold maximum increase in the inactivation rate constant. Significantly, reconstitution of such NaCl-TMF-2 membranes with the 17 and 23 kDa proteins reverted both the pH dependency and the inactivation rate constant to that of TMF-2. A hierarchy of effectivity for solubilization of Mn and protein, which was highly correlated with inactivation of the Mn-S-state enzyme, was observed among NH₂OH and its derivatives. This same hierarchy was observed irrespective of prior depletion of the 17 and 23 or the 17, 23 and 33 kDa proteins from TMF-2. The hierarchy of effectivity among derivatives was: NH₂OH > CH₃NHOH > NH₂NH₂, NH₂OSO₃ > NH₂OCH₃ ⪢ CH₃NHOCH₃, NH₄Cl. The function(s) of the extrinsic PS II proteins as determinants of the reactivity of the Mn-S-state complex with polar amine vs other type compounds is discussed.     

Methanogenesis in Big Soda Lake, Nevada: an Alkaline, Moderately Hypersaline Desert Lake

Incubated sediment slurries from Big Soda Lake, Nevada, produced significant levels of CH₄, and production was inhibited by 2-bromoethanesulfonic acid and by autoclaving. Methane production was stimulated by methanol, trimethylamine, and, to a lesser extent, methionine. Surprisingly, hydrogen, acetate, and formate amendments provided only slight or no stimulation of methanogenesis. Methane production by sediment slurries had a pH optimum of 9.7. A methanol-grown enrichment culture containing a small, epifluorescent coccus as the predominant organism was recovered from sediments. The enrichment grew best when FeS or autoclaved sediment particles were included in the media, had a pH optimum of 9.7, and produced ¹⁴CH₄ from ¹⁴CH₃OH. The methane formed by methanolgrown enrichment cultures was depleted in ¹³C by 72 to 77‰ relative to the methanol.     

Tris(triazolyl)borate ligands of intermediate steric bulk for the synthesis of biomimetic structures with hydrogen bonding and solubility in hydrophilic solvents

Tris(triazolyl)borate ligands (Ttz) of intermediate steric bulk were synthesized to investigate their potential for hydrogen bonding and improved solubility in hydrophilic solvents as applied to biomimetic chemistry. The crystal structure of 3-phenyl-5-methyl-1,2,4-triazole (Htz^Ph,Me) revealed hydrogen bonding and π stacking interactions. The new ligand salt, potassium tris(3-phenyl-5-methyl-1,2,4-triazolyl)borate (KTtz^Ph,Me) was synthesized as the first example of a Ttz ligand of intermediate steric bulk. Metathesis between KTtz^Ph,Me and NaCl followed by recrystallization produced [NaTtz^Ph,Me] · 6CH₃OH in which the geometry around the sodium is octahedral with an unusual N₃O₃ donor set; this structure also shows that a hydrogen bonding network is formed by methanol molecules and triazole nitrogens. (Ttz^Ph,Me)ZnCl was synthesized and characterized crystallographically as [(Ttz^Ph,Me)ZnCl] · 0.5CH₃OH in which the zinc is tetrahedral and the triazole rings are within hydrogen bonding distance of CH₃OH. All of these new compounds are methanol soluble to varying degrees and Htz^Ph,Me and KTtz^Ph,Me are soluble in methanol/water mixtures.     

N-(o-carboxybenzyl) chitosans: Novel chelating polyampholytes

The imine formed by chitosan with phthalaldehydic acid was reduced with sodium cyanoborohydride and the resulting N-(o-carboxybenzyl) chitosan (NCBC) was insolubilised with ethanol and acetone and obtained as a white, free-flowing powder, soluble in both acidic and alkaline solutions. A sample of NCBC with the following degrees of substitution: acetamido 42%±4%, N-(o-carboxybenzyl) amine 43%±3%, free amine 15%±1% and containing 16%±1% moisture, was characterised by IR and UV-Vis. spectrometry, titration and viscometry. The isoelectric point was 6·8; the pK_a values were 5·7 and 8·0. NCBC could be determined by UV-Vis. spectrophotometry in aqueous solutions at 274 nm; maximum viscosity of the solutions was observed at pH 4. Upon addition of NCBC to transition metal ion solutions (0·1–0·5 mm) chelation and insolubilisation took place immediately. The dependence of the collection percentage on pH, NCBC and metal ion concentrations was studied for nine metal ions.     

Interaction of the cholesterol reducing agent simvastatin with zwitterionic DPPC and charged DPPG phospholipid membranes

Simvastatin is a lipid-lowering drug in the pharmaceutical group statins. Interaction of a drug with lipids may define its role in the system and be critical for its pharmacological activity. We examined the interactions of simvastatin with zwitterionic dipalmitoyl phosphatidylcholine (DPPC) and anionic dipalmitoyl phosphatidylglycerol (DPPG) multilamellar vesicles (MLVs) as a function of temperature at different simvastatin concentrations using Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). The FTIR results indicate that the effect of simvastatin on membrane structure and dynamics depends on the type of membrane lipids. In anionic DPPG MLVs, high simvastatin concentrations (12, 18, 24 mol%) change the position of the CH₂ antisymmetric stretching mode to lower wavenumber values, implying an ordering effect. However, in zwitterionic DPPC MLVs, high concentrations of simvastatin disorder systems both in the gel and liquid crystalline phases. Moreover, in DPPG and DPPC MLVs, simvastatin has opposite dual effects on membrane dynamics. The bandwidth of the CH₂ antisymmetric stretching modes increases in DPPG MLVs, implying an increase in the dynamics, whereas it decreases in DPPC MLVs. Simvastatin caused broadening of the phase transition peaks and formation of shoulders on the phase transition peaks in DSC curves, indicating multi-domain formations in the phospholipid membranes. Because physical features of membranes such as lipid order and fluidity may be changed with the bioactivity of drugs, opposing effects of simvastatin on the order and dynamics of neutral and charged phospholipids may be critical to deduce the action mechanism of the drug and estimate drug-membrane interactions.     

Planar tetrameric metal cluster formation at room temperature induced by π?π interactions: 3D supramolecular host containing 1D channel filled with solvent methanol

A novel tetrameric metal cluster, [La₂(phen)₃(2,3-pdc)(NO₃)₄(H₂O)]₂·(CH₃OH)₂ (2,3-pdcH₂ = pyridine-2,3-dicarboxylic acid, phen = 1,10-phenanthroline), have been synthesized at room temperature from water-methanol mixture by mixing the reactants in stoichiometric ratio. 2,3-Pdc and their π?π interactions played a vital role on the construction of the core. The auxiliary ligand, phen, which blocked the outermost periphery of the molecule and their hydrophobic π?π interactions facilitate the formation of the tetrameric metal clusters. The tetrameric metal clusters are connected by supramolecular interactions to form 3D supramolecular metal organic host (MOSH) producing supramolecular channels along a-axis. These supramolecular channels are filled up by solvent methanol molecules. The luminescent investigations reveal that cluster complex exhibits strong blue emission.     

Synthesis, crystal structures and magnetic properties of the copper(II) complexes containing isophthalate anion as coligand

Two new dinuclear isophthalato-bridged copper(II) complexes [Cu₂(ntb)₂(μ-ipt)](ClO₄)₂·4CH₃OH·0.33H₂O (1), [Cu₂(bbma)₂(μ-ipt)(NO₃)(CH₃OH)]NO₃·CH₃OH (2) and one mononuclear complex [Cu(bbma)(ipt)(CH₃OH)_0.67(H₂O)_0.33]·2CH₃OH (3) containing tetradentate and tridentate poly-benzimidazole ligands were synthesized, where ntb is tris(2-benzimidazolylmethyl)amine, bbma is bis(benzimidazol-2-yl-methyl)amine and ipt is isophthalate dianion. All of the complexes were characterized by elemental analysis, IR spectra and X-ray crystallography. The structures of complexes 1 and 2 consist of μ-ipt bridging two Cu(II) centers in a bis(monodentate) bonding fashion. The coordination geometry around the Cu(II) ions of both compounds has a distorted square pyramidal geometry. The Cu···Cu distances are 9.142 and 10.435 Å for 1 and 2, respectively. Complex 3 has a distorted square pyramidal geometry achieved by the three N-atoms of the bbma ligand, one isophthalate-oxygen atom and one oxygen atom from a coordinated methanol molecule. The magnetic susceptibility measurements at variable temperature over the 2-300 K range for complexes 1 and 2 are reported, with J values to be −0.013 and −0.32 cm⁻¹, respectively. The results show that the two complexes exhibit very weak antiferromagnetic interactions between the dinuclear copper(II) centers.     

Copper sorption by chitosan in the presence of citrate ions: influence of metal speciation on sorption mechanism and uptake capacities

The presence of organic ligands in a solution containing metal ions modifies metal speciation, which in turn changes the sorption mechanism, optimum pH range and maximum sorption capacity. The present work investigates the sorption of copper by chitosan in the presence of citrate at different metal/ligand ratios. Copper uptake in acidic solution takes place through electrostatic attraction between the protonated amine groups of chitosan and anionic copper-citrate complexes (mainly Cu(OH)L2- but also a small fraction of CuL-). Sorption was negligible below pH 3 due to competition from dissociated anionic ligand and counter ions brought about by dissociation of the acid used for pH control. Actually, copper sorption begins to be significant when the fraction of anionic copper-complexes exceeds that of anionic copper-free ligand. So sorption capacity strongly increases up to pH 4.5-5.5. Above pH 5.5, the progressive decrease of amine protonation leads to a linear decrease in sorption capacity. An excess of ligand leads to an increase in the fraction of free dissociated (anionic) ligand that may compete for electrostatic attraction on protonated amine groups and therefore leads to a decrease in sorption capacities.     

Diffusivity of CH4 In Model Silica Nanopores: Molecular Dynamics and Quasichemical Mean Field Theory

Equilibrium molecular dynamics and dual control volume grand canonical molecular dynamics experiments were carried out aiming at the investigation of the dependence of transport diffusivity upon the adsorbent pore size and sorbate concentration of CH₄ in cylindrical silica nanopores at 298?K, calibrated with respect to experimental data of zeolite VPI 5; the results of simulation were elaborated on the basis of the quasichemical mean field approximation via a theoretical model for surface diffusion. Our mapping procedure between simulation and quasichemical theory reveals that sorbate–sorbate energetics emerge as the physical reason for the variation of corrected (Darken) and hence transport diffusivity with respect to pore size and sorbed phase fractional occupancy.     

Trophic links between fermenters and methanogens in a moderately acidic fen soil

Trophic links between fermentation and methanogenesis of soil derived from a methane‐emitting, moderately acidic temperate fen (pH 4.5) were investigated. Initial CO₂:CH₄ production ratios in anoxic microcosms indicated that methanogenesis was concomitant to other terminal anaerobic processes. Methane production in anoxic microcosms at in situ pH was stimulated by supplemental H₂–CO₂, formate or methanol; supplemental acetate did not stimulate methanogenesis. Supplemental H₂–CO₂, formate or methanol also stimulated the formation of acetate, indicating that the fen harbours moderately acid‐tolerant acetogens. Supplemental monosaccharides (glucose, N‐acetylglucosamine and xylose) stimulated the production of CO₂, H₂, acetate and other fermentation products when methanogenesis was inhibited with 2‐bromoethane sulfonate 20 mM. Glucose stimulated methanogenesis in the absence of BES. Upper soil depths yielded higher anaerobic activities and also higher numbers of cells. Detected archaeal 16S rRNA genes were indicative of H₂–CO₂‐ and formate‐consuming methanogens (Methanomicrobiaceae), obligate acetoclastic methanogens (Methanosaetaceae) and crenarchaeotes (groups I.1a, I.1c and I.3). Molecular analyses of partial sequences of 16S rRNA genes revealed the presence of Acidobacteria, Nitrospirales, Clamydiales, Clostridiales, Alpha‐, Gamma‐, Deltaproteobacteria and Cyanobacteria. These collective results suggest that this moderately acidic fen harbours phylogenetically diverse, moderately acid tolerant fermenters (both facultative aerobes and obligate anaerobes) that are trophically linked to methanogenesis.     

Nitric oxide and pH modulation in gynaecological cancer

Nitric oxide plays several roles in cellular physiology, including control of the vascular tone and defence against pathogen infection. Neuronal, inducible and endothelial nitric oxide synthase (NOS) isoforms synthesize nitric oxide. Cells generate acid and base equivalents, whose physiological intracellular concentrations are kept due to membrane transport systems, including Na⁺/H⁺ exchangers and Na⁺/HCO₃^? transporters, thus maintaining a physiological pH at the intracellular (~7.0) and extracellular (~7.4) medium. In several pathologies, including cancer, cells are exposed to an extracellular acidic microenvironment, and the role for these membrane transport mechanisms in this phenomenon is likely. As altered NOS expression and activity is seen in cancer cells and because this gas promotes a glycolytic phenotype leading to extracellular acidosis in gynaecological cancer cells, a pro‐inflammatory microenvironment increasing inducible NOS expression in this cell type is feasible. However, whether abnormal control of intracellular and extracellular pH by cancer cells regards with their ability to synthesize or respond to nitric oxide is unknown. We, here, discuss a potential link between pH alterations, pH controlling membrane transport systems and NOS function. We propose a potential association between inducible NOS induction and Na⁺/H⁺ exchanger expression and activity in human ovary cancer. A potentiation between nitric oxide generation and the maintenance of a low extracellular pH (i.e. acidic) is proposed to establish a sequence of events in ovarian cancer cells, thus preserving a pro‐proliferative acidic tumour extracellular microenvironment. We suggest that pharmacological therapeutic targeting of Na⁺/H⁺ exchangers and inducible NOS may have benefits in human epithelial ovarian cancer.     

Substituent effect of the stacking interaction between carbon monoxide and benzene

Noncovalent interactions (NCIs) between carbon monoxide and substituted benzene were investigated at the M06-2X/6-311++G(d,p) level. rThe results of interaction energy analysis indicated different effects for the electron-donating (–NH₂, –OH, –CH₃) and electron-withdrawing (–F, –CN, –NO₂) groups on the CO?PhX complex. Atoms in molecules analysis confirmed the NCIs between CO and PhX. NCI analysis revealed that these interactions belong to van der Waals interactions. The electron density shift of the complexes was investigated with electron density difference analysis. Ternary CO?PhX?Bz complexes were designed to study the interplay between CO?π and π?π stacking interactions.     

Amine transport at the plasmalemma of Riccia fluitans

Green thallus cells of the aquatic liverwort, Riccia fluitans, are rapidly depolarized in the presence of 1–20 μM NH₄Cl and 5–100 μM CH₃NH₃Cl, respectively. Simultaneously, the membrane conductance is increased from 0.41 to 1.2 S · m^?2. Uptake of [¹⁴C]methylamine is stimulated by increasing [K⁺]_o and inhibited by increasing [Na⁺]_o or [H⁺]_o, is highly voltage sensitive, and saturates at low amine concentrations.Double-reciprocal plots of (a) maximal membrane depolarization and (b) methylamine uptake vs. external amine concentration give apparent K_m values of 2 ± 1 μM ammonia and 25–50 μM methylamine; K_m values for changes in conductance and membrane current are greater and voltage dependent. Whereas the amine transport into the cell is strongly inhibited by CN^?, the amine efflux is stimulated.The current-voltage characteristics of the ammonia transport are represented by a sigmoid curve with an equilibrium potential of ?60 mV, and this is understood as a typical carrier curve with a saturation current of about 70 mA · m^?2. It is further concluded that the evidently carrier-mediated transport is competitive for the two amines tested, and that ammonia and methylamine are transported in the protonated form as NH₄⁺ and CH₃NH₃⁺ into the cytoplasm.     

Reactions of methylcobalamin with tin and lead compounds

Reactions of CH₃[Co] with (CH₃)_nM^(4?n)+ (n = 2, 3; M = Sn, Pb) at concentrations high enough to detect (CH₃)₄M in the head space (yields 7.08×10^?5?2.06×10^?5%), indicate that dismutation is the major route of production. Similarly, kinetic reactions at lower concentrations show that no demethylation of CH₃[Co] by (CH₃)₃M⁺ (M = Sn, Pb) occurs after 60 days. From the methylation of SnCl₂ by CH₃[Co] at pD 1.0 and under aerobic conditions, the following hydrolysis species were observed in the 400 MHz ¹H NMR spectrum: CH₃- Sn(OH)Cl₂·2H₂O (63.6%), [CH₃Sn(OH)(H₂O)₄]²⁺ (17.6%) and CH₃Sn(OH)₂Cl·nH₂O (18.8%). No methylation products were observed from similar reactions with Pb(II) salts.     

Tandem crystallization strategies for resolution of 3,3,3‐trifluorolactic acid [CF3CH(OH)COOH] by chiral benzylamines

Resolution of rac‐3,3,3‐trifluorolactic acid by diastereomeric salt formation was reinvestigated. The use of (S)‐1‐phenylethylamine gives coprecipitation of two diastereomeric phases, 1 (S)‐[NH₃CH(CH₃)Ph](S)‐[CF₃CH(OH)COO] and 2 (S)‐[NH₃CH(CH₃)Ph](R)‐[CF₃CH(OH)COO]·H₂O. Pure phase 1 may be obtained using molecular sieves as desiccants. Resolution by (S,S)‐2‐amino‐1‐phenylpropan‐1,3‐diol gives monoclinic (S,S)‐[NH₃CH(CH₂OH)CHOHPh] (R)‐[CF₃CH(OH)‐COO] 3 with minor (S)‐3,3,3‐trifluorolactate contamination, which is precluded in the recrystallized orthorhombic form 4 . A new resolution using inexpensive phenylglycinol gives pure phase 5 (S)‐[NH₃CH(CH₂OH)Ph] (S)‐[CF₃CH(OH)COO] in 76% yield, 94% ee in a single step, in preference to its (S)‐(R) diastereomer 6 . Overall efficient resolution for both enantiomers of the trifluorolactic acid (each ca. 70% yield, 99% ee) may be achieved by various two‐step “tandem” crystallizations, involving direct addition of either water or a second base to the filtrate from the initial reaction.     

A Stand‐Alone Si‐Based Porous Photoelectrochemical Cell

Wireless photoelectrochemical (PEC) devices promise easy device fabrication as well as reduced losses. Here, the design and fabrication of a stand‐alone ion exchange material‐embedded, Si membrane‐based, photoelectrochemical cell architecture with micron‐sized pores is shown, to overcome the i) pH gradient formation due to long‐distance ion transport, ii) product crossover, and iii) parasitic light absorption by application of a patterned catalyst. The membrane‐embedded PEC cell with micropores utilizes a triple Si junction cell as the light absorber, and Pt and IrO_x as electrocatalysts for the hydrogen evolution reactions and oxygen evolution reactions, respectively. The solar‐to‐hydrogen efficiency of 7% at steady‐state operation, as compared to an unpatterned η_PV of 10.8%, is mainly attributed to absorption losses by the incorporation of the micropores and catalyst microdots. The introduction of the Nafion ion exchange material ensures an intrinsically safe PEC cell, by reducing the total gas crossover to <0.1%, while without a cation exchange membrane, a crossover of >6% is observed. Only in a pure electrolyte of 1 m H₂SO₄, a pH gradient‐free system is observed thus completely avoiding the build‐up of a counteracting potential.