Diazo complexes of osmium: preparation of binuclear derivatives with bis(aryldiazene) and bis(aryldiazenido) bridging ligands

Depending on experimental conditions and the nature of the phosphite, the reaction of OsH₂P₄ [P=P(OEt)₃ and PPh(OEt)₂] with bis(aryldiazonium) salts [N₂Ar-ArN₂](BF₄)₂ [Ar-Ar=4,4^′-C₆H₄-C₆H₄, 4,4^′-(2-CH₃)C₆H₃-C₆H₃(2-CH₃), 4,4^′-C₆H₄-CH₂-C₆H₄ and 1,5-C₁₀H₆] afford the cis and the trans binuclear [{OsHP₄}₂(μ-HNNAr-ArNNH)](BPh₄)₂1, 2 aryldiazene derivatives. These complexes 1, 2 further react with the mono(diazonium) (4-CH₃C₆H₄N₂)BF₄ salt to give the bis(aryldiazene) [{Os(4-CH₃C₆H₄NNH)P₄}₂(μ-HNNAr-ArNNH)](BPh₄)₄3, 4 derivatives. Binuclear bis(aryldiazenido) [{OsP₄}₂(μ-N₂Ar-ArN₂)](BPh₄)₂ (6) [P=P(OEt)₃; Ar-Ar=4,4^′-C₆H₄-C₆H₄, 4,4^′-C₆H₄-CH₂-C₆H₄] complexes were prepared by deprotonating with NEt₃ the nitrile-diazene [{Os(4-CH₃C₆H₄CN)P₄}₂(μ-HNNAr-ArNNH)](BPh₄)₄ (5) derivatives. The aryldiazenido compounds 6 react with HCl to give the new aryldiazene [{OsClP₄}₂(μ-HNNAr-ArNNH)](BPh₄)₂ (7) derivatives. The characterisation of the complexes by IR and ¹H, ³¹P, ¹⁵N NMR data is also discussed. The reaction of the hydride OsH₂(PPh₂OEt)₄ with mono(diazonium) salts was also studied and led exclusively to the mono(aryldiazene) [OsH(ArN NH)(PPh₂OEt)₄]BPh₄ (8) (Ar=C₆H₅, 4-CH₃C₆H₄) derivatives. Spectroscopic data (¹H, ³¹P, ¹⁵N NMR) on ¹⁵N-labelled derivatives suggest the presence of two isomers with the N-bonded and the π-bonded ArNNH ligand, respectively.     

The Abiotic Formation of Hydrocarbons from Dissolved CO2 Under Hydrothermal Conditions with Cobalt-Bearing Magnetite

Conversion of CO₂ to organic compounds in hydrothermal systems is important in understanding prebiotic chemical evolution leading to the origin of life. However, organic compounds with carbon number of more than 3 have never been produced from dissolved CO₂ in simulated hydrothermal experiments. In this paper, we report that not only CH₄, C₂H₆ and C₃H₈, but also n-C₄H₁₀ and n-C₅H₁₂ could be produced from dissolved CO₂ and H₂ in the presence of cobalt-bearing magnetite at 300°C and 30 MPa. It is shown that unbranched alkanes in Anderson–Schulz–Flory distribution were the dominant hydrocarbon products produced from dissolved CO₂ catalyzed by cobalt-bearing magnetite under certain hydrothermal conditions. It is proposed that magnetite with other transition metals may act potentially as effective mineral catalysts for abiotic formation of organic compounds from dissolved CO₂ in hydrothermal systems.     

Co-function of C3-and C4-photosynthetic pathways in C3, C4 and C3-C4 intermediate Flaveria species

The potential for C₄ photosynthesis was investigated in five C₃-C₄ intermediate species, one C₃ species, and one C₄ species in the genus Flaveria, using ¹⁴CO₂ pulse-¹²CO₂ chase techniques and quantum-yield measurements. All five intermediate species were capable of incorporating ¹⁴CO₂ into the C₄ acids malate and aspartate, following an 8-s pulse. The proportion of ¹⁴C label in these C₄ products ranged from 50–55% to 20–26% in the C₃-C₄ intermediates F. floridana Johnston and F. linearis Lag. respectively. All of the intermediate species incorporated as much, or more, ¹⁴CO₂ into aspartate as into malate. Generally, about 5–15% of the initial label in these species appeared as other organic acids. There was variation in the capacity for C₄ photosynthesis among the intermediate species based on the apparent rate of conversion of ¹⁴C label from the C₄ cycle to the C₃ cycle. In intermediate species such as F. pubescens Rydb., F. ramosissima Klatt., and F. floridana we observed a substantial decrease in label of C₄-cycle products and an increase in percentage label in C₃-cycle products during chase periods with ¹²CO₂, although the rate of change was slower than in the C₄ species, F. palmeri. In these C₃-C₄ intermediates both sucrose and fumarate were predominant products after a 20-min chase period. In the C₃-C₄ intermediates, F. anomala Robinson and f. linearis we observed no significant decrease in the label of C₄-cycle products during a 3-min chase period and a slow turnover during a 20-min chase, indicating a lower level of functional integration between the C₄ and C₃ cycles in these species, relative to the other intermediates. Although F. cronquistii Powell was previously identified as a C₃ species, 7–18% of the initial label was in malate+aspartate. However, only 40–50% of this label was in the C-4 position, indicating C₄-acid formation as secondary products of photosynthesis in F. cronquistii. In 21% O₂, the absorbed quantum yields for CO₂ uptake (in mol CO₂·[mol quanta]^-1) averaged 0.053 in F. cronquistii (C₃), 0.051 in F. trinervia (Spreng.) Mohr (C₄), 0.052 in F. ramosissima (C₃-C₄), 0.051 in F. anomala (C₃-C₄), 0.050 in F. linearis (C₃-C₄), 0.046 in F. floridana (C₃-C₄), and 0.044 in F. pubescens (C₃-C₄). In 2% O₂ an enhancement of the quantum yield was observed in all of the C₃-C₄ intermediate species, ranging from 21% in F. ramosissima to 43% in F. pubescens. In all intermediates the quantum yields in 2% O₂ were intermediate in value to the C₃ and C₄ species, indicating a co-function of the C₃ and C₄ cycles in CO₂ assimilation. The low quantum-yield values for F. pubescens and F. floridana in 21% O₂ presumably reflect an ineffcient transfer of carbon from the C₄ to the C₃ cycle. The response of the quantum yield to four increasing O₂ concentrations (2–35%) showed lower levels of O₂ inhibition in the C₃-C₄ intermediate F. ramosissima, relative to the C₃ species. This indicates that the co-function of the C₃ and C₄ cycles in this intermediate species leads to an increased CO₂ concentration at the site of ribulose-1,5-bisphosphate carboxylase/oxygenase and a concomitant decrease in the competitive inhibition by O₂.Abbreviations PEP phosphoenolpyruvate - PGA 3-phosphoglycerate - RuBP ribulose-1,5-bisphosphate     

New κ-PNN′- and κ-PNN′O-polydentate ligands: Synthesis, coordination and structural studies

The three-step synthesis of new mixed P/N/N′/O-donor ligands C₆H₃(OH){2-NHC(O)CH₂NCHC₆H₄PPh₂}(4-CH₃) 3a·HH and C₆H₄(OH){3-NHC(O)CH₂NCHC₆H₄PPh₂} 3b·HH, by Schiff base condensation of the 1° amines C₆H₃(OH){2-NHC(O)CH₂NH₂}(4-CH₃) 2a or C₆H₄(OH){3-NHC(O)CH₂NH₂} 2b with C₆H₄(CHO)(2-PPh₂) in refluxing EtOH, is described. Reaction of 1 equiv. of 3a·HH or 3b·HH with MCl₂(cod) (M = Pt, Pd; cod = cycloocta-1,5-diene) affords the κ²-PN-chelate complexes MCl₂(3a·HH) (M = Pd 4a; M = Pt 4b) and MCl₂(3b·HH) (M = Pt 4c). The dichlorometal(II) complexes 4d and 4e, bearing instead a pendant 4-phenolic group, were similarly prepared (in >90% yield). Chloro-bridge cleavage of [Pd(μ-Cl)(η³-C₃H₅)]₂ with 3a·HH or 3b·HH gave the monocationic κ²-PN-chelate complexes [Pd(η³-C₃H₅)(3a·HH)]Cl 5a or [Pd(η³-C₃H₅)(3b·HH)]Cl 5b, respectively. Elimination of cod, and single CH₃ protonation, from Pt(CH₃)₂(cod) upon reaction with 1 equiv. of 3a·HH or 3b·HH in C₇H₈ at room temperature afforded the neutral complexes C₆H₃(OH){2-NC(O)CH₂NCHC₆H₄PPh₂Pt(CH₃)}(4-CH₃) 6a and C₆H₄(OH){3-NC(O)CH₂NCHC₆H₄PPh₂Pt(CH₃)} 6b, respectively bearing a monoanionic (3a·H⁻ or 3b·H⁻) κ³-PNN′-tridentate ligand. Amide and phenol deprotonation were readily achieved, using KO^tBu as base, to give high yields of the κ⁴-PNN′O-tetradentate complexes C₆H₃(O){2-NC(O)CH₂NCHC₆H₄PPh₂Pd}(4-CH₃) 7a and C₆H₃(O){2-NC(O)CH₂NCHC₆H₄PPh₂Pt}(4-CH₃) 7b bearing the dianionic ligand 3a²⁻. All new compounds have been characterised by multinuclear NMR, FTIR, mass spectroscopy and microanalysis. Single crystal X-ray studies have been performed on compounds 1b·1.5CH₂Cl₂, 3b·HH·0.5Et₂O, 6b·CHCl₃ and 7b·0.5Et₂O.     

An examination of the advantages of C3-C4 intermediate photosynthesis in warm environments

Abstract. The photosynthetic responses to temperature in C₃, C₃-C₄ intermediate, and C₄ species in the genus Flaveria were examined in an effort to identify whether the reduced photorespiration rates characteristic of C₃-C₄ intermediate photosynthesis result in adaptive advantages at warm leaf temperatures. Reduced photorespiration rates were reflected in lower CO₂ compensation points at all temperatures examined in the C₃-C₄ intermediate, Flaveria floridana, compared to the C₃ species, F. cronquistii. The C₃-C₄ intermediate, F. floridana, exhibited a C₃-like photosynthetic temperature dependence, except for relatively higher photosynthesis rates at warm leaf temperatures compared to the C₃ species, F. cronquistii. Using models of C₃ and C₃-C₄ intermediate photosynthesis, it was predicted that by recycling photorespired CO₂ in bundle-sheath cells, as occurs in many C₃-C₄ intermediates, photosynthesis rates at 35°C could be increased by 28%, compared to a C₃ plant. Without recycling photorespired CO₂, it was calculated that in order to improve photosynthesis rates at 35°C by this amount in C₃ plants, (1) intercellular CO₂ partial pressures would have to be increased from 25 to 31 Pa, resulting in a 57% decrease in water-use efficiency, or (2) the activity of RuBP carboxylase would have to be increased by 32%, resulting in a 22% decrease in nitrogen-use efficiency. In addition to the recycling of photorespired CO₂, leaves of F. floridana appear to effectively concentrate CO₂ at the active site of RuBP carboxylase, increasing the apparent carboxylation efficiency per unit of in vitro RuBP carboxylase activity. The CO₂-concentrating activity also appears to reduce the temperature sensitivity of the carboxylation efficiency in F. floridana compared to F. cronquistii. The carboxylation efficiency per unit of RuBP carboxylase activity decreased by only 38% in F. floridana, compared to 50% in F. cronquistii, as leaf temperature was raised from 25 to 35°C. The C₃-C₄ intermediate, F. ramosissima, exhibited a photosynthetic temperature temperature response curve that was more similar to the C₄ species, F. trinervia, than the C₃ species, F. cronquistii. The C₄-like pattern is probably related to the advanced nature of C₄-like biochemical traits in F. ramosissima The results demonstrate that reductions in photorespiration rates in C₃-C₄ intermediate plants create photosynthetic advantages at warm leaf temperatures that in C₃ plants could only be achieved through substantial costs to water-use efficiency and/or nitrogen-use efficiency.     

Evaluating adsorbed-phase activity coefficient models using a 2D-lattice model

Despite the wide use of the real adsorbed solution theory to predict multicomponent adsorption equilibrium, the models used for the adsorbed phase activity coefficients are usually borrowed from the gas–liquid phase equilibria. In this work, the accuracy of the Wilson and NRTL models for evaluating adsorbed phase activity coefficients is tested using a 2D-lattice model. An accurate model for adsorbed-phase activity coefficients should have no problem in fitting adsorption data obtained using this simple lattice model. The results, however, show that the commonly used Wilson and NRTL models cannot describe the adsorbed phase activity coefficients for slightly non-ideal to strong non-ideal mixtures. Therefore, until new models for adsorbed phase activity coefficients are developed, we should use existing models for liquids with care. In the second part of this work, the use of Monte Carlo simulations on a segregated 2D-lattice model, for predicting adsorption of mixtures is investigated. The segregated model assumes that the competition for adsorption occurs at isolated adsorption sites, and that the molecules from each adsorption site interact with the bulk phase independently. Two binary mixtures in two adsorbent materials were used as case studies for testing the predictions of the segregated 2D-lattice model: the binary system CO₂–N₂ in the hypothetical pure silica zeolite PCOD8200029, with isolated adsorption sites and normal preference for adsorption, and the binary system CO₂–C₃H₈ in pure silica mordenite (MOR), with isolated adsorption sites and inverse site preference. The segregated 2D-lattice model provides accurate predictions for the system CO₂–N₂ in PCOD8200029 but fails in predicting the adsorption behaviour of CO₂–C₃H₈ in pure silica MOR. The predictions of the segregated ideal adsorbed solution theory model are superior to those of the 2D-lattice model.     

Evidence for σ → η3 rearrangement reaction in gaseous ions from Fe,Mn and Re allylic derivatives

The fragmentation pathways of (η³-C₃H₄X)FeCO)₂NO, (σ-C₃H₄X)Fe(CO)₂(NO)L, (η³-C₃H₄X)Fe(CO)(NO)L, (σ-C₃H₄X)Fe(CO)₂(NO)L′, (η³- C₃H₄X)Fe(CO)(NO)L′, (σ-C₃H₅)M(CO)₅, (η³-C₃H₅)M(CO)₄, (σ-CH₂CHC(Me)₂)Mn(CO)₅, (η³-CH₂ CHC(Me)₂)Mn(CO)₄, (X=2-Cl; L=PPh₃; L′= P(OMe)₃; M=Mn, Re) have been investigated by mass spectrometry. In the σ derivatives the molecular ion loses CO or the allylic ligand, while in the η³ derivative loss of a CO group is the only fragmentation mode of the molecular ion. Electron impact as well as methane chemical ionization mass spectra have been reported. Kinetic energy release of selected metastable ions indicates that a σ → η³ rearrangement reaction occurs.     

Effect of varying environments on photosynthetic parameters of C3, C3-C4 and C4 species of Panicum

Summary CO₂ exchange characteristics and the activity of the carboxylating enzymes phosphoenolpyruvate carboxylase (PEP-C, E.C. 4.1.1.31) and ribulose 1,5-bisphosphate carboxylase (RuBP-C, E.C. 4.1.1.39) during one year in the greenhouse and at two levels of light and temperature in growth chambers were determined in the C₃-C₄ intermediate species P. milioides Nees ex. Trin. These results were compared with those of P. bisulcatum Thumb. (C₃) and P. maximum Jacq. (C₄). Under all tested conditions, and even when the influence of leaf surface temperature on photosynthetic rates and CO₂ compensation points were measured, the biochemical and physiological behaviour of the C₃-C₄ intermediate was more similar to that of the C₃ plant than the C₄ species. The C₄ plant P. maximum, however, responded positively, mainly in terms of PEP-C activity and photosynthetic rate, to the regime of high light and temperature. The results presented indicate that in the C₃-C₄ Panicum grown in high light and temperature no direct relationships between a low CO₂ compesation point and superior growth are evident. It has still to be clarified why in nature a photosynthetic-photorespiratory pathway leading to an intermediate CO₂ compensation value has evolved in P. milioides.     

Reassimilation of carbon dioxide by Flaveria (Asteraceae) species representing different types of photosynthesis

The capability to reassimilate CO₂ originating from intracellular decarboxylating processes connected with the photorespiratory glycolate pathway and-or decarboxylation of C₄ acids during C₄ photosynthesis has been investigated with four species of the genus Flaveria (Asteraceae). The C₃-C₄ intermediate species F. pubescens and F. anomala reassimilated CO₂ much more efficiently than the C₃ species F. cronquistii and, with respect to this feature, behaved similarly to the C₄ species F. trinervia. Therefore, under atmospheric conditions the intermediate species photorespired with rates only between 10–20% of that measured with F. cronquistii. At low oxygen concentrations (1,5%) the reassimilation potential of F. anomala approached that of F. trinervia and was distinct from that found with F. pubescens. The data are discussed with respect to a possible sequence of events during evolution of C₄ photosynthesis. If compared with related data for C₃-C₄ intermediate species from other genera they support the hypothesis that, during evolution of C₄ photosynthesis, an efficient capacity for CO₂ reassimilation evolved prior to a CO₂-concentrating mechanism.Abbreviations C₃, C₄ assimilated CO₂ initially found in 3-phosphoglycerate (C₃) or malate and aspartate (C₄) - D reassimilation coefficient - R _n , R _t net, total CO₂ evolution as measured with 0.03 and 3% CO₂, respectively - RuBP ribulose-1,5-bisphosphate - TPS true photosynthesis     

A spectroscopic and molecular dynamic approach on the interaction between ionic liquid type gemini surfactant and human serum albumin

The interactions of imidazolium bashed ionic liquid-type cationic gemini surfactant ([C₁₂-4-C₁₂im]Br₂) with HSA were studied by fluorescence, time-resolved fluorescence, UV-visible, circular dichroism, molecular docking and molecular dynamic simulation methods. The results showed that the [C₁₂-4-C₁₂im]Br₂ quenched the fluorescence of HSA through dynamic quenching mechanism as confirmed by time-resolved spectroscopy. The Stern–Volmer quenching constant (K_sv) and relevant thermodynamic parameters such as enthalpy change (ΔH), Gibbs free energy change (ΔG) and entropy change (ΔS) for interaction system were calculated at different temperatures. The results revealed that hydrophobic forces played a major role in the interactions process. The results of synchronous fluorescence, UV-visible and CD spectra demonstrated that the binding of [C₁₂-4-C₁₂im]Br₂ with HSA induces conformational changes in HSA. Inquisitively, the molecular dynamics study contribute towards understanding the effect of binding of [C₁₂-4-C₁₂im]Br₂ on HSA to interpret the conformational change in HSA upon binding in aqueous solution. Moreover, the molecular modelling results show the possible binding sites in the interaction system.     

PHOTOSYNTHETIC CHARACTERISTICS OF C3-C4 INTERMEDIATE FLAVERIA FLORIDANA (ASTERACEAE) IN NATURAL HABITATS: EVIDENCE OF ADVANTAGES TO C3-C4 PHOTOSYNTHESIS AT HIGH LEAF TEMPERATURES

Measurements of leaf gas exchange were conducted in situ for the C₃-C₄ intermediate plant Flaveria floridana. Leaves exhibited measurable CO₂ assimilation at atmospheric CO₂ concentrations as low as 20 μmol/mol. This result demonstrates that the low CO₂ compensation points observed in past studies of greenhouse-grown C₃-C₄ intermediate plants also exist in plants growing in their natural habitat. Photosynthesis rates in F. floridana were near their maximum at intercellular CO₂ concentrations as low as 112 μmol/mol. The existence of near-maximum photosynthesis rates at such low intercellular CO₂ concentrations is interpreted as evidence for the existence of a CO₂-concentrating mechanism in F. floridana. Such a mechanism would also explain the observed lack of response in photosynthesis rates to reductions in stomatal conductance and intercellular CO₂ concentration as the leaf-to-air water vapor concentration gradient is increased. Photosynthetic rates were relatively high at leaf temperatures between 35 and 40 C, compared to most C₃ plants. At midday during May, when leaf temperatures were between 35 and 42 C, F. floridana leaves exhibited photosynthesis rates that were four times higher than a sympatric C₃ species (Eustoma exaltatum) of similar growth form and ecological habit. The high photosynthesis rates at high leaf temperatures in F. floridana were not due to higher leaf nitrogen contents, but rather to its reduced rate of photorespiration. These results confirm that C₃-C₄ intermediate photosynthesis can provide plants with an advantage at high leaf temperatures, compared to C₃ plants.     

Versatility of pyridine-2-methanol as a chelating ligand toward a manganese ion: synthesis and X-ray structural analysis on some manganese-pyridine-2-methanol derivatives

A systematic synthesis and X-ray structural analysis have been made for several manganese derivatives with pyridine-2-methanol as a chelating ligand; neutral Mn(C₅NH₄-2-CH₂OH)₂(C₆F₅CO₂)₂ (1), trans-[Mn(C₅H₄N-2-CH₂-OH)₂{C₆F₄-1,4-(CO₂)₂}]_∞ (2), cis-[Mn(C₅H₄N-2-CH₂-OH)₂{C₆F₄-1,3-(CO₂)₂}]_∞ (3), {Mn(C₅H₄N-2-CH₂-OH)₂(4,4^′-bipyridine)(ClO₄)}_∞ (4), and Mn(C₅H₄N-2-CH₂-OH)₃(ClO₄)₂(4,4-azopiridine) (pyridine-2-methanol) (5) are our results. 1 and 5 are monomers, while 2-4 are polymers. An oxidation state of the manganese ion in 1, 2, 3, and 5 is 2⁺, while that of 4 is suggested to be 3⁺. The magnetic data of 4 down to 2 K are measured. The length of the linker ligand has been suggested to afford a crucial effect on the dimensionality of the product.     

Comparative ultrastructure and gas exchange characteristics of the C3–C4 intermediate Neurachne minor S. T. Blake (Poaceae)

Abstract Ultrastructural and physiological characteristics of the C₃-C₄ intermediate Neurachne minor S. T. Blake (Poaceae) are compared with those of C₃ and C₄ relatives, and C₃-C₄Panicum milioides Nees ex Trin. N. minor consistently exhibits very low CO₂ compensation points (τ: 1.0, usually 0.3–0.6 Pa) yet has C₃-like δ¹³C values. CO₂ assimilation rates (A) respond like those of C₃ plants to a decrease in O₂ partial pressure (2 × 104–1.9 × 103 Pa) at ambient CO₂ levels, but this response is progressively attenuated until negligible at very low CO₂. By contrast, other species of the Neurachneae are clearly either C₄ (two spp.) or C₃ (seven spp.). For plants grown and measured at different photon flux densities (PFDs), τ for N. minor and P. milioides increases from 0.5 to 1.0, and from 1.0 to 2.1 Pa, respectively, as PFD is decreased from 1860 to 460 μmol m^?2s^?1. In N. minor, the O₂ response of τ is either biphasic as in P. milioides, but much diminished and with a higher transition point, or is very C₄-like. As in C₄ relatives, inner sheath cells contain numerous chloroplasts. Their walls possess a suberized lamella, which may make them more CO₂-tight than bundle sheath cells of P. milioides, contributing to the almost C₄-like τ characteristics of N. minor. The biochemical basis of C₃-C₄ intermediacy is considered.     

Effect of substituents at phenyl group of 7,7′-dioxo-9,9′-epoxylignane on antifungal activity

Using 21 newly synthesized 7,7′-dioxo-9,9′-epoxylignane derivatives having a modified 7-phenyl group, we examined the relationship between their structure and antifungal activity against plant pathogens such as Bipolaris oryzae to determine the effects of various substituents on the antifungal activity. Compared with the lead compound having a 4-OH-3-CH₃O-phenyl moiety, several analogs showed higher antifungal activity against B. oryzae, including the compound having an unsubstituted phenyl group and those having either of the following phenyl substituents: 2-OH, 4-CH₃O, 4-C₂H₅O, 4-n-C₃H₇O, 4-n-C₄H₉O, 4-CF₃O, 4-C₂H₅, or 4-Cl. On the other hand, the activity of compounds having a branched substituent, such as 4-i-C₃H₇O or 4-i-C₃H₇, on the 7-phenyl group or a multi-substituted phenyl group was equipotent or inferior to that of the lead compound. These results as well as correlations between the antifungal activity of the test compounds and the physicochemical parameters of the varied substituents suggest that the position of substitution on the 7-phenyl group and the incorporation of substituents with optimal physicochemical properties are important for exerting the antifungal activity.     

Ionic metallomesogens derived from silver(I) bis-amine complexes: Structure and mesogenic behavior

Complexes [Ag(NH₂R)₂]X, (X = NO₃, R = -C₆H₄-C_nH_2n+1-p, -C₆H₄-O-C_nH_2n+1-p, -CH₂-C₆H₄-O-C_nH_2n+1-p, n = 6, 8, 10, 12, 14; X = BF₄, R = -CH₂-C₆H₄-O-C_nH_2n+1-p, n = 6, 8, 10, 12, 14; X = OAc, R = -CH₂-C₆H₄-O-C₁₀H₂₁-p; X = CF₃SO₃, R = -CH₂-C₆H₄-O-C₁₀H₂₁-p) have been prepared. They all show S_A mesophases corresponding to two kinds of structures, already present in the solid state. The alkylaniline and alkoxyaniline derivatives adopt a bilayered structure where the cation has an extended centrosymmetric conformation. The benzylamine derivatives contain U-shaped cations giving rise to a bilayered structure which allows microsegregation of the organic part of the molecule from the inorganic Ag?(anion) part. Some degree of interdigitation of the terminal chains is observed for all the complexes with aryl containing ligands.     

Simulation of separation of C2H6 from CH4 using zeolitic imidazolate frameworks

Separation of important chemical feedstocks, such as C₂H₆ from natural gas, can greatly benefit the petrochemical industry. In this paper, the grand canonical Monte Carlo method has been used to study the adsorption and separation of CH₄ and C₂H₆ in zeolites, isoreticular metal-organic framework-1 (IRMOF-1) and zeolitic imidazolate frameworks (ZIFs) with different topology, including soadlite, gmelinite and RHO topologies. Compared with mordenite zeolite and IRMOF-1, ZIFs and mordenite framework inverted (MFI) zeolite have better separation performance for C₂H₆/CH₄ mixtures at different mole fractions of C₂H₆. From the study of equilibrium snapshots and density distribution profiles, adsorption sites could be grouped as (1) sites with strong interactions with adsorbent and (2) sites with strong interactions with surrounding adsorbates. The gas molecules occupied the first site and then went on to occupy the second site. In CH₄/C₂H₆ mixture adsorption/separation, the adsorption of CH₄ was confined by the existence of C₂H₆. Due to energetic effect, C₂H₆ selectivity was affected by temperature at a low-pressure range, but did not change as much in a high-pressure range because of packing effect in micropore. In binary adsorption, large C₂H₆ molecules favour sites with strong adsorbent interactions. At high pressures, packing effects played an important role and it became easy for small CH₄ molecules to access the sites with strong adsorbate interactions.     

Comparative reactivity study of cyclopentadienyl and fulvalene molybdenum complexes

The reactions of cis-1,1′-[η⁵:η⁵-(C₅H₃CO₂Me)₂]Mo₂(CO)₆ (1), in the presence of 1 equiv. of Me₃NO, and [(η⁵-C₅H₄CO₂Me)Mo(CO)₃]₂ (2) with dppe produce CO labilization and formation of the dinuclear zwitterions trans-1,1′-[η⁵:η⁵-(C₅H₃CO₂Me)₂]Mo₂(CO)₅(dppe) (3) and disproportionation species [(η⁵-C₅H₄CO₂Me)Mo(CO)₂(dppe)]⁺ [(η⁵-C₅H₄CO₂Me)Mo(CO)₃]⁻ (4), respectively. Using the same method, the reactions of trans-1,1′-[η⁵:η⁵-(C₅H₃CO₂Me)₂]Mo₂(CO)₆I₂ and (η⁵-C₅H₄CO₂Me)Mo(CO)₃I with PPh₃ in the presence of 1 and 2 equiv. of Me₃NO yield trans-1,1′-[η⁵:η⁵-(C₅H₃CO₂Me)₂]Mo₂(CO)₄(PPh₃)₂I₂ (5) and (η⁵-C₅H₄CO₂Me)Mo(CO)₂(PPh₃)I (6). The reactions of the several anionic carbonyl species {trans-1,1′-[η⁵:η⁵-(C₅H₃CO₂Me)₂]Mo₂(CO)₆}²⁻, [(η⁵:η⁵-C₁₀H₈)W₂(CO)₆]²⁻ and [(η⁵-C₅H₄CO₂Me)Mo(CO)₃]⁻ with S₂Ph₂ give rise to the thiolate–fulvalene complexes cis-1,1′-[η⁵:η⁵-(C₅H₃CO₂Me)₂]Mo₂(CO)₄(μ-SPh)₂ (7) and (η⁵:η⁵-C₁₀H₈)W₂(CO)₆(SPh)₂ (8) and the thiolate-bridged dimer [(η⁵-C₅H₄CO₂Me)Mo(CO)(μ-SPh)]₂ (9). Treatment of 6 with 1 equiv. of HCCCCH and with (η⁵-C₅H₅)Mo(CO)(dppe)(CCCCH), in the presence of CuI at room temperature, afford the cyclopentadiene complexes (η⁵-C₅H₄CO₂Me)Mo(CO)₂(PPh₃)(CCCCH) (10) and (η⁵-C₅H₄CO₂Me)(PPh₃)(CO)₂Mo(CCCC)Mo(CO)(dppe)(η⁵-C₅H₅) (11), respectively. The reaction of (η⁵-C₅H₅)Mo(CO)(dppe)(CCCCH) with Co₂(CO)₈ yields [Co₂{μ-HC₂CC[Mo(CO)(dppe)(η⁵-C₅H₅)]}(CO)₆] (12). All the new compounds have been characterized by analytical and spectroscopic methods.     

Effect of oxygen partial pressure on nitrogen fixation and acetylene reduction in a sandy loam soil amended with glucose

Summary Small samples of soil amended with 2% (w/w) of glucose were preincubated either aerobically or anaerobically and then assayed (N₂ ¹⁵ and C₂H₂-C₂H₄) either aerobically or anaerobically for different time periods. One-hour C₂H₂-C₂H₄ assays showed greatest activity when anaerobic assay followed anaerobic preincubation. During the anaerobic preincubation a lag of 12–24 h occurred before rapid increase in one-hour assay activity was observed. When aerobic assay followed aerobic preincubation a longer lag was observed and lower activities were obtained. When anaerobic assay followed aerobic preincubation (orvice versa) negligible activities were observed in short assays, and longer assays showed increasing activity related to changes in atmosphere and/or microbial population in the closed system. Preincubation of soil on a diffusion gradient at a series of different partial pressures of oxygen confirmed the above pattern and showed that as preincubation pO₂ increased, the anaerobic assay activity rapidly decreased. As preincubation pO₂ decreased from 0.2 atm the aerobic assay activity decreased but less rapidly. The activities observed were related to the sizes of the Azotobacter and Clostridium populations. There was no evidence of aerobic or anaerobic C₂H₂ reduction in any cultures of ‘oligonitrophiles’ isolated. Incorporation of N₂ ¹⁵ was related to C₂H₂ reduction activity in the soil system studied. However, observed C₂H₄/N₂ molar ratios ranged from 10 to 22 and appeared to be highest in samples which were preincubated anaerobically. Issued as Macdonald College Journal Series No.618 and as Canadian IBP contribution No.84.     

Effect of H2-CO2 on Methanogenesis from Acetate or Methanol in Methanosarcina spp

Growth of Methanosarcina sp. strain 227 and Methanosarcina mazei on H₂-CO₂ and mixtures of H₂-CO₂ and acetate or methanol was examined. The growth yield of strain 227 on H₂-CO₂ in complex medium was 8.4 mg/mmol of methane produced. Growth in defined medium was characteristically slower, and cell yields were proportionately lower. Labeling studies confirmed that CO₂ was rapidly reduced to CH₄ in the presence of H₂, and little acetate was used for methanogenesis until H₂ was exhausted. This resulted in a biphasic pattern of growth similar to that reported for strain 227 grown on methanol-acetate mixtures. Biphasic growth was not observed in cultures on mixtures of H₂-CO₂ and methanol, and less methanol oxidation occurred in the presence of H₂. In M. mazei the aceticlastic reaction was also inhibited by the added H₂, but since the cultures did not immediately metabolize H₂, the duration of the inhibition was much longer.     

Evidence for Deuterium Retention in the Products after Enzymatic C-C and Ether Bond Cleavages of Deuterated Lignin Model Compounds

The mechanism of C-C and ether bond cleavages of C_α-or C_β-deuterated β-O-4 and β-l lignin substructure models and the vicinal diol compounds catalyzed by the enzyme system from Phanerochaete chrysosporium culture was investigated. The enzymatic oxidation of β-O-4 lignin model compounds in the presence of H₂O₂ and O₂ yielded C₆-C_α-derived benzaldehyde, and C_β-C_γ-derived product together with the arylglycerol product. Likewise, the β-l models and the diol compounds also underwent the C-C bond cleavage, yielding C₆-C_β-derived benzaldehyde and the arylglycol product. The results demonstrated that the d-labels at C_α and C_β of the substrates were retained in the products after the C_α-C_β and ether bond cleavages.