The first solvation shell of magnesium ion in a model protein environment with formate,water, and X-NH3, H2S,imidazole, formaldehyde,and chloride as ligands: An ab initio study

The first coordination shell of an Mg(II) ion in a model protein environment is studied. Complexes containing a model carboxylate, an Mg(II) ion, various ligands (NH₃, H₂S, imidazole, and formaldehyde) and water of hydration about the divalent metal ion were geometry optimized. We find that for complexes with the same coordination number, the unidentate carboxylate–Mg(II) ion is greater than 10 kcal mol^?1 more stable than the bidentate orientation. Imidazole was found to be the most stable ligand, followed in order by NH₃ formaldehyde, H₂O, and H₂S. © 1995 Wiley-Liss, Inc.     

Effects of gypsum on the uptake,assimilation and cycling of 15N-labelled ammonium and nitrate-N by perennial ryegrass

Solution culture studies have shown that plant uptake of NH₄ ⁺ and NO₃ ^- can be improved by increasing the concentration of Ca²⁺ in the root environment: the same may be true for grass grown in soil culture. An experiment was set up to see whether gypsum (CaSO₄ 2H₂O) increased the rate at which perennial ryegrass absorbed ¹⁵NH₄ ⁺ and ¹⁵NO₃ ^- from soil.The results demonstrated that gypsum increases the rates of uptake of both NH₄ ⁺ and NO₃ ^- by perennial ryegrass. However because there was little potential for mineral-N loss from the experimental system, either by gaseous emission or by N immobilization, long term improvements in fertilizer efficiency were not observed. Nitrogen cycling from shoots to roots commenced once net uptake of N into plants had ceased. Labelled N transferred thus to roots underwent isotopic exchange with unlabelled soil N. It was suggested that this exchange of N might constitute an energy drain from the plant, if plant organic N was exchanged for soil inorganic N. The fact that the exchange occurred at all cast doubt on the suitability of the ¹⁵N-isotope dilution technique for assessing fertilizer efficiency in medium to long term experiments. There was evidence that the extra NO₃ ^--N taken up by plants on the all-nitrate treatments as a result of gypsum application, was reduced in root tissue rather than in shoots, but to the detriment of subsequent root growth and N uptake.     

Asymmetric Zinc‐Catalyzed Hydrosilylation of Ketones and the Effect of Carboxylate on the Enantioselectivity

Several chiral ligands containing (R,R)‐diaminocyclohexane moieties and pyrrole, furan, or benzene have been synthesized. These ligands were tested in enantioselective zinc‐catalyzed hydrosilylation reactions; excellent enantioselectivities were obtained when the ligands containing (R,R)‐diaminocyclohexane moieties and furan rings were used. For comparison, zinc chloride combined with different potassium carboxylate salts and ligands were also tested for catalytic hydrosilylation reactions. Chirality 25:275–280, 2013. © 2013 Wiley Periodicals, Inc.     

Room Temperature Processed Highly Efficient Large‐Area Polymer Solar Cells Achieved with Molecular Engineering of Copolymers

The room temperature (RT) processability of the photoactive layers in polymer solar cells (PSCs) from halogen‐free solvent along with their highly reproducible power conversion efficiencies (PCEs) and intrinsic thickness tolerance are extremely desirable for the large‐area roll‐to‐roll (R2R) production. However, most of the photoactive materials in PSCs require elevated processing temperatures due to their strong aggregation, which are unfavorable for the industrial R2R manufacturing of PSCs. These limiting factors for the commercialization of PSCs are alleviated by synthesizing random terpolymers with components of (2‐decyltetradecyl)thiophen‐2‐yl)naphtho[1,2‐c:5,6‐c′]bis[1,2,5]thiadiazole and bithiophene substituted with methyl thiophene‐3‐carboxylate (MTC). In contrast to the temperature‐dependent PNTz4T polymer, the resulting random terpolymers (PNTz4T‐MTC) show better solubility, slightly reduced crystallinity and aggregation, and weaker intermolecular interaction, thus enabling PNTz4T‐MTC to be processed at RT from a halogen‐free solvent. Particularly, the PNTz4T‐5MTC‐based photoactive layer exhibits an excellent PCE of 9.66%, which is among the highest reported PCEs for RT and ecofriendly halogen‐free solvent processed fullerene‐based PSCs, and a thickness tolerance with a PCE exceeding 8% from 100 to 520 nm. Finally, large‐area modules fabricated with the PNTz4T and PNTz4T‐5MTC polymer have shown 4.29% and 6.61% PCE respectively, with an area as high as 54.45 cm² in air.     

Design, synthesis and anti-microbial activity of 1H-pyrazole carboxylates

In a SAR study, we have synthesized a few 1H-pyrazole carboxylate related microbicides using Vilsmeier reagent. The anti-microbial screening results of 1H-pyrazole-3-carboxylate are reported here for the first time. The effect of 1H-pyrazole carboxylates on the mycelial growth of plant pathogenic fungi is revealed. The first X-ray structure in the family of microbicidal 1H-pyrazole-4-carboxylates is presented.     

Synthesis and structure of the first sulfur-donor adduct of a diruthenium tetracarboxylate

The first sulfur-donor adduct of a diruthenium tetracarboxylate, [Ru₂(μ-O₂CCH₃)₄(THT)₂]PF₆ (1), where THT=tetrahydrothiophene, has been synthesized and characterized by X-ray diffraction, IR and UV-Vis spectroscopy, magnetic susceptibility and electrochemistry. Complex 1 displays a typical RuRu bond length of 2.285(4) Å but a very long RuS axial bond of 2.627(13) Å. The redox potential for the [Ru₂(μ-O₂CCH₃)₄(THT)₂]^+/0 couple is −322 mV (vs. Fc/Fc⁺) which is comparable to other moderately strong Lewis base adducts. Axial ligand binding is driven by σ-donation with little π-backdonation from the metal centers.     

Effects of external phosphorus supply on internal phosphorus concentration and the initiation,growth and exudation of cluster roots in Hakea prostrata R.Br.

The response of internal phosphorus concentration, cluster-root initiation, and growth and carboxylate exudation to different external P supplies was investigated in Hakea prostrata R.Br. using a split-root design. After removal of most of the taproot, equal amounts of laterals were allowed to grow in two separate pots fastened together at the top, so that the separate root halves could be exposed to different conditions. Plants were grown for 10 weeks in this system; one root half was supplied with 1 M P while the other halves were supplied with 0, 1, 25 or 75 M P. Higher concentrations of P supplied to one root half significantly increased the P concentration of those roots and in the shoots. The P concentrations in root halves supplied with 1 M P were invariably low, regardless of the P concentration supplied to the other root half. Cluster root initiation was completely suppressed on root halves supplied with 25 or 75 M P, whereas it continued on the other halves supplied with 1 M P indicating that cluster-root initiation was regulated by local root P concentration. Cluster-root growth (dry mass increment) on root halves supplied with 1 M P was significantly reduced when the other half was either deprived of P or supplied with 25 or 75 M P. Cluster-root growth was favoured by a low shoot P status at a root P supply that was adequate for increased growth of roots and shoots without increased tissue P concentrations. The differences in cluster-root growth on root halves with the same P supply suggest that decreased cluster-root growth was systemically regulated. Carboxylate-exudation rates from cluster roots on root halves supplied with 1 M P were the same, whether the other root half was supplied with 1, 25 or 75 M P, but were approximately 30 times faster when the other half was deprived of P. Estimates of root P-uptake rates suggest a rather limited capacity for down-regulating P uptake when phosphate was readily available.     

Metabolic products and pathways of fluorotelomer alcohols in isolated rat hepatocytes

Fluorotelomer alcohols (FTOHs; CF(3)(CF(2))(x)C(2)H(4)OH; where x=3, 5, 7, 9) are a novel class of polyfluorinated contaminants, recently detected in the North American atmosphere, that are possible precursors to the series of perfluoroalkyl carboxylates (PFCAs) in human blood. An in vivo rat study validated earlier independent work that poly- and per-fluoroalkyl carboxylates were metabolites of FTOHs, but our detection of several novel metabolites prompted us to examine their pathways in greater detail using isolated rat hepatocytes. Using 8:2 FTOH (i.e. where x=7) as a model compound, the metabolic products formed by isolated rat hepatocytes were identified, and three synthesized intermediates were incubated separately to elucidate the metabolic pathways. For 8:2 FTOH, a major fate was direct conjugation to form the O-glucuronide and O-sulfate. Using 2,4-dinitrophenylhydrazine (DNPH) trapping, the immediate oxidation product of 8:2 FTOH was identified as 8:2 fluorotelomer aldehyde (8:2 FTAL; CF(3)(CF(2))(7)CH(2)C(H)O). 8:2 FTAL was transient and eliminated HF non-enzymatically to yield 8:2 fluorotelomer alpha,beta-unsaturated aldehyde (8:2 FTUAL; CF(3)(CF(2))(6)CFCHC(H)O) which was also short-lived and reacted GSH and perhaps other endogenous nucleophiles. Four polyfluorinated acid intermediates were also detected, including 8:2 fluorotelomer carboxylate (8:2 FTCA; CF(3)(CF(2))(7)CH(2)C(O)O(-)), 8:2 fluorotelomer alpha,beta-unsaturated carboxylate (8:2 FTUCA; CF(3)(CF(2))(6)CFCHC(O)O(-)), tetrahydroperfluorodecanoate (CF(3)(CF(2))(6)(CH(2))(2)CO(2)(-)), and dihydroperfluorodecenoate (CF(3)(CF(2))(6)CHCHCO(2)(-)). The pathways leading to 8:2 FTCA and FTUCA involve oxidation of 8:2 FTAL, however, the pathways leading to the latter two polyfluorinated acids remain inconclusive. The fate of the unsaturated metabolites, 8:2 FTUAL and FTUCA, included conjugation with GSH and dehydrofluorination to yield alpha,beta-unsaturated GSH conjugates, and GS-8:2 FTUAL which was subsequently reduced to the corresponding alcohol. Perfluorooctanoate (PFOA) and minor amounts of perfluorononanoate (PFNA) were confirmed as metabolites of 8:2 FTOH, and the respective roles of beta- and alpha-oxidation mechanisms are discussed. The analogous acids, aldehydes, and conjugated metabolites of 4:2, 6:2, and 10:2 FTOH (i.e. where x=3, 5, and 9, respectively) were also detected, and metabolite profiles among FTOHs generally differed only in the length of their perfluoroalkyl chains. Preincubation with aminobenzotriazole, but not pyrazole, inhibited the formation of metabolites from all FTOHs, suggesting that their oxidation was catalyzed by P450, not alcohol dehydrogenase.     

A new copper(II) complex of unsymmetrical tetradentate ligand generated in situ: synthesis and molecular structure

A new copper(II) complex with tetradentate unsymmetrical ligand was prepared by one-pot condensation of methyl-2-pyrrole carboxylate, diethylenetriamine and copper(II) sulfate. The complex was characterized by elemental analysis, electronic and IR spectral, as well as X-ray crystal structure determination. The X-ray structure of the molecule reveals the copper(II) center is in a square planar environment through coordination by two nitrogen atoms of the amine, one amide nitrogen atom and one nitrogen atom of the pyrrole moieties, respectively. The copper(II) complex is neutral due to deprotonation of the amide and pyrrole groups.