OH Mixtures Research Articles

Microwave‐Assisted Synthesis of SrTiO3 Nanocuboids without TiCl4

Strontium titanate (STO) nanocuboids are a novel support for Pt nanoparticle catalysts (Pt/STO). The first of many steps in commercializing Pt/STO will be developing a scalable, environmentally sustainable, and cost‐effective STO nanocuboid synthesis. Herein, Sr–Ti–OH mixtures are synthesized from various Sr2+ and Ti4+ reagents and treated by convection‐ and microwave‐assisted heating to obtain STO nanoparticles. These experiments clarify how phase composition of the prehydrothermal Sr–Ti–OH mixture and choice of heating method affect final nanoparticle morphology. In Sr–Ti–OH mixtures synthesized with TiCl4, STO is the most stable phase and precipitates prior to heating, while titania sol–gels are the most stable phase when other Ti4+ sources are used. STO nanocrystals always form when Sr–Ti–OH mixtures are treated by convection heating, though nanocuboids are only observed if STO precipitates from the Sr–Ti–OH mixture. Microwave‐assisted hydrothermal treatment more rapidly heats the precursor solution, and thus, STO nanocuboids can form from a variety of Sr–Ti–OH mixtures regardless of mixture composition. Two microwave syntheses of STO nanocuboids are reported: one which uses TiCl4 as a Ti4+ source, and another that uses titanium(IV) bis(ammonium lactato) dihydroxide ([NH4CH3CH(O)CO2]2Ti(OH)2), a water‐stable Ti4+ complex.

Effect of ethanol addition on the laminar burning velocities of gasoline surrogates

Laminar burning velocities (LBV) and Markstein lengths of spherical flames of n-heptane (H), iso-octane (O), and ethanol (E) and their binary and ternary mixtures (in equal volume fractions) at elevated pressures and temperatures are experimentally investigated. Measurements are performed in a constant volume combustion vessel using two distinct techniques: flame front imaging and pressure rise rate. For pure components, ethanol shows a higher LBV compared to n-heptane and iso-octane at same conditions. A pressure dependence on LBV of each pure component is observed where ethanol is found to have the strongest pressure dependence. This is also indicated by the higher negative coefficients in three-body termination reactions through a sensitivity analysis. For binary mixtures, the EH mixture was found to have the highest LBVs compared to other blends. The pressure dependence on LBV of ethanol is also present in binary mixtures where at a higher pressures the EO blend is found to have a lower LBV compared to the OH blend due to competing reactions against the H radical pool. Non-linear behaviour of the EH mixture’s LBV was observed and verified through the chemical kinetics suggesting the widely used mixing rules for blends might need additional improvements, especially at higher temperatures. An equal volume EHO ternary mixture shows the LBV to be similar to the OH mixture at 380 K. At 450 K, the LBVs differ by 7% at atmospheric pressure, but due to ethanol’s pressure dependence, this difference decreases to zero as the pressure increases to 4 bar.

Self-Assembling of Fmoc-GC Peptide Nucleic Acid Dimers into Highly Fluorescent Aggregates.

The study of molecules that self-assemble through noncovalent interactions is one of the most attractive topics in supramolecular chemistry. The use of short peptides or modified nucleotides as building blocks for the aggregates is particularly intriguing because these are very easy to synthesize; moreover, subtle changes in the chemical structure of such building blocks may drastically affect the properties of the aggregates. The ability of peptide nucleic acids (PNA) to aggregate has been very little explored, despite its practical applications. In this work we investigated the self-assembling properties of a PNA dimer, conjugated at the N-terminus to a fluorenylmethoxycarbonyl group. This PNA dimer forms nano-aggregates at low concentration in CHCl3 /CH3 OH mixtures. The aggregates retain very interesting fluorescent properties (high quantum yield in the visible region with lifetimes on the nanosecond scale), which make them promising materials for applications in optoelectronics.

Rapid and Complete Dissolution of Softwood Biomass in Tetra-n-butylphosphonium Hydroxide with Hydrogen Peroxide

The wood dissolution properties of tetra-n-butylphosphonium hydroxide ([P4,4,4,4]OH) were investigated. Cedar wood meal was treated with several concentrations of aqueous (aq.) [P4,4,4,4]OH with hydrogen peroxide (H2O2) in a glass tube at 121 °C. The solution of 60% aq. [P4,4,4,4]OH with H2O2 at 121 °C showed the best dissolution capability for woody biomass with a high dissolution rate of 0.152 g min-1. Under this condition, 98.5% of the woody biomass, including both lignin and holocellulose, was dissolved after 3 h of treatment. The molecular weight distribution of lignin in the soluble fraction of the [P4,4,4,4]OH mixtures was determined via size exclusion chromatography, and its weight-average molecular weight decreased from approximately 7500 g/mole after 0.5 h to 2 h of treatment to 5700 g/mole after 3 h and 2500 g/mole after 5 h of treatment. Lower molecular weight components were determined by high-performance liquid chromatography, and vanillin and vanillic acid were identified. The dissolved cellulose was precipitated, and its polymerization degree decreased significantly after 0.5 h of treatment compared to that of the original cellulose.

Interstellar ice analogs: H2O ice mixtures with CH3OH and NH3in the far-IR region

Context. New spectroscopic observations in the far-infrared (IR) range are expected from future planned missions. Although water ice is the only species detected so far in interstellar ices in this range, the presence of ice mixtures requires laboratory characterization of the corresponding spectra.Aims. We present an investigation on far-IR spectra of binary ice mixtures relevant in various astrophysical environments. The foremost goal is to compare the spectroscopic features of the ice mixtures to those of pure ices, and to search for changes in peak frequencies, intensities, and band strengths of the main bands.Methods. Mixtures H2 O:CH3 OH and H2 O:NH3 of different ratios have been deposited on a diamond substrate at astrophysically relevant conditions. We measured the spectra in the near- and mid-IR regions to derive ice column densities that were subsequently used to calculate the apparent band strengths in the far-IR region. We also designed theoretical models to study these mixtures and to predict their spectra.Results. We recorded spectra of amorphous phases for H2 O:CH3 OH mixtures of different compositions, that is 1:1, 3:1, and 10:1 at 8 K, and compared these mixtures to those obtained after warming. This process involves the appearance of new spectral features and changes in band shapes and band strengths. We also compared the spectra to those of the pure species and to theoretical predictions. We measured apparent band strengths for all the observed features. For H2 O:NH3 mixtures, the ratios selected were 3:1, 1:1, and 1:3. In this case the spectral variations are even more marked than for the water:methanol samples. Conclusions. Band strengths in the far-IR are missing in astrophysics literature for ice mixtures. The results presented here are valuable for detecting the presence and composition of such mixtures from future space observations in this spectral region.

Preparation and Characterization of Water Perm-selectivity ZSM-5 Zeolite Membrane Using Fluoride Route

Water perm-selectivity ZSM-5 zeolite membranes were prepared from fluoride media without organic template on the low cost macroporous α-Al2O3 tubular support by secondary growth. A varying temperature hot dip-coating method with different size of crystal was used to form a flat and continuous perfect seed layer. The effects of concentration of the small seed solution on the surface of seed layer, the morphology and pervaporation property of the ZSM-5 membrane were investigated. The results show that when the concentration of the small seed solution is 0.2wt%, the prepared ZSM-5 zeolite membrane displays high water perm-selectivity properties in the pervaporation dehydration of 10wt% H2O/IPA and 10wt% H2O/Ac OH mixtures at 75℃, which fluxes are 3.64 kg/(m2·h) and 0.61 kg/(m2·h), separation factor up to 3204 and 1321, respectively.

Relative permittivity measurements of Et–OH and Mt–OH mixtures for calibration standards in 1–15 GHz range

In open-ended coaxial dielectric characterisation techniques, intermediate liquid standards between air and water are necessary for precise dielectric measurements of biological samples. Calibration standards with dielectric permittivities much different from those of the measured samples will produce unreliable results. Different intermediate calibration standards are prepared and measurement results are presented. The aim is to obtain various permittivity values between 10 and 80 by diluting methanol and ethanol with distilled water. This technique can also be used for assessing the purity of alcohols.

Facile Method for Modulating the Profiles and Periods of Self-Ordered Three-Dimensional Alumina Taper-Nanopores

We report a facile nanofabrication method, one-step hard anodizing and etching peeling (OS-HA-EP) of aluminum foils followed by multistep mild anodizing and etching pore-widening (MS-MA-EW), for the controllable tailoring of hexagonally packed three-dimensional alumina taper-nanopores. Their profiles can be precisely tailored by the synergistic control of anodizing time, etching time and cyclic times at the MS-MA-EW stage, exemplified by linear cones, whorl-embedded cones, funnels, pencils, parabolas, and trumpets. Meantime, their periods can also be modulated in the range of 70-370 nm by choosing matched anodizing electrolytes (e.g., H(2)C(2)O(4), H(2)SO(4), H(2)C(2)O(4)-H(2)SO(4), and H(2)C(2)O(4)-C(2)H(5)OH mixture) and anodizing voltages at the OS-HA-EP stage. We also demonstrated that the long-range ordering of nanopits and the peak voltage of stable self-ordered HA, which are unachievable in a single H(2)C(2)O(4) electrolyte system, can be effectively tuned by simply adding tiny quantity of H(2)SO(4) and C(2)H(5)OH to keep an appropriate HA current density, respectively. This method of using the combination of simple pure chemical nanofabrication technologies is very facile and efficient in realizing the controllable tailoring of large-area alumina membranes containing self-ordered taper-nanopores. Our work opens a door for exploring the novel physical and chemical properties of different materials of nanotaper arrays.

Methanol ice on the surface of minor bodies in the solar system

Aims. Spectral analyses of trans-Neptunan objects (TNOs) and of the linked Centaurs, which are supposed to be among the most primitive minor bodies in the solar system, reveal some chemical and physical properties of their surface. To determine the surface composition of these objects and their surface evolution is essential for gaining clues on the conditions under which the solar system has been formed. Methods. Chemical composition and physical properties of the surface of three objects have been constrained by computing the depth of the absorption features of the spectra in the near-infrared, running spectral models based on radiative transfer theory in the [0.4-2.3] μm range, and analyzing new laboratory measurements of the spectral behavior of thin samples of H 2 O-CH 3 OH mixtures. Results. Our investigations allow us to confirm the presence of CH 3 OH ice on the surface of the Centaur (5145) Pholus and the resonant (55638) TNO 2002 VE 95 . It may also possibly be found on the classical TNO (120348) 2004 TY 364 . Our laboratory experiments indicate that the behavior of the methanol and water ice absorption bands is dependent on the ambient temperature and the dilution level of the mixture. These results also suggest that methanol may be diluted in water ice on the surface of the Centaur Pholus. Conclusions. Formation and destruction processes of methanol suggest that a part (at least) of the surface of these objects is younger than the solar system age. If confirmed, this shows that primordial ices could still be detected on the surface of objects that are submitted to irradiation and rejuvenation processes.

The Quest for New Mild and Selective Modifications of Natural Structures: Laccase‐Catalysed Oxidation of Ergot Alkaloids Leads to Unexpected Stereoselective C‐4 Hydroxylation

Laccase-catalysed oxidation of ergot alkaloids in the absence of chemical mediators allowed the unexpected isolation of the mono-hydroxylated derivatives of compounds 2-7. Structure determination by NMR techniques clearly indicated that hydroxylation took place at the C-4 benzylic position. Quite notably, the proposed protocol allowed, for the first time, functionalisation at the C-4 position of the ergoline skeleton. Depending on the absence or on the presence of a C-10 α-methoxy substituent, hydroxylation was either stereoselective (furnishing C-4α OH derivatives) or gave rise to a C-4α/C-4β OH mixture in a 2:1 ratio, respectively.

Identification and Behavioral Evaluation of Sex Pheromone Components of the Chinese Pine Caterpillar Moth, Dendrolimus tabulaeformis

BackgroundThe Chinese pine caterpillar moth, Dendrolimus tabulaeformis Tsai and Liu (Lepidoptera: Lasiocampidae) is the most important defoliator of coniferous trees in northern China. Outbreaks occur over enormous areas and often lead to the death of forests during 2–3 successive years of defoliation. The sex pheromone of D. tabulaeformis was investigated to define its chemistry and behavioral activity.Methodology/Principal FindingsSex pheromone was collected from calling female D. tabulaeformis by headspace solid phase microextraction (SPME) and by solvent extraction of pheromone glands. Extracts were analyzed by coupled gas chromatography/mass spectrometry (GC-MS) and coupled GC-electroantennographic detection (GC-EAD), using antennae from male moths. Five components from the extracts elicited antennal responses. These compounds were identified by a combination of retention indices, electron impact mass spectral matches, and derivatization as (Z)-5-dodecenyl acetate (Z5-12:OAc), (Z)-5-dodecenyl alcohol (Z5-12:OH), (5Z,7E)-5,7-dodecadien-1-yl acetate (Z5,E7-12:OAc), (5Z,7E)-5,7-dodecadien-1-yl propionate (Z5,E7-12:OPr), and (5Z,7E)-5,7-dodecadien-1-ol (Z5,E7-12:OH). Behavioral assays showed that male D. tabulaeformis strongly discriminated against incomplete and aberrant blend ratios. The correct ratio of Z5,E7-12:OAc, Z5,E7-12:OH, and Z5,E7-12:OPr was essential for optimal upwind flight and source contact. The two monoenes, Z5-12:OAc and Z5-12:OH, alone or binary mixtures, had no effect on behavioral responses when added to the optimal three-component blend.Conclusions/SignificanceThe fact that deviations from the optimal ratio of 100∶100∶4.5 of Z5,E7-12:OAc, Z5,EZ7-12:OH, and Z5,E7-12:OPr resulted in marked decreases in male responses suggests that biosynthesis of the pheromone components is precisely controlled. The optimal blend of the sex pheromone components of D. tabulaeformis worked out in this study should find immediate use in monitoring this pest in Chinese forests.

Formation of methyl formate after cosmic ion irradiation of icy grain mantles

Context. Methyl formate (HCOOCH3 ) is a complex organic molecule detected in hot cores and hot corinos. Gas-phase chemistry fails to reproduce its observed abundance, which usually varies between 10-7 and 10-9 with respect to H2 .Aims. Laboratory experiments were performed in order to investigate a solid-state route of methyl formate formation, to obtain an estimate of the amount that can be formed, and to verify whether it can account for the observed abundances.Methods. Several solid samples (16 K) of astrophysical interest were analyzed by infrared spectroscopy in the 4400-400 cm-1 range. The infrared spectral characteristics of frozen methyl formate were studied by deriving their band strength values. The effects produced upon warm-up of the samples were analyzed comparing the spectra taken at different temperatures. In order to study the formation and destruction mechanism of methyl formate in the interstellar ices, a binary mixture of methanol (CH3 OH) and carbon monoxide (CO) ice and a sample of pure methanol were irradiated at 16 K with 200 keV protons. Methyl formate was identified through its fundamental mode (CH3 rocking) at about 1160 cm-1 . Results. We present the mid-infrared methyl formate ice spectrum showing both the amorphous (16 K) and the crystalline (110 K) structure. We report novel measurements of the band strength values of the six main methyl formate bands. We prove the formation and the destruction of methyl formate after irradiation of CH3 OH and a CO:CH3 OH mixture. Extrapolating our results to the interstellar medium conditions we found that the production timescale of methyl formate agrees well with the evolutionary time of molecular clouds. The comparison with the observational data indicates that the amount of methyl formate formed after irradiation can account for the observed abundances.Conclusions. The present results allow us to suggest that gas phase methyl formate observed in dense molecular clouds is formed in the solid state after cosmic ion irradiation of icy grain mantles containing CO and CH3 OH and released to the gas phase after desorption of icy mantles.

Phase Behavior and Rheological Properties of Salt-Free Catanionic Surfactant Mixtures in the Presence of Bile Acids

The phase behavior, rheological properties, and structures of two salt-free catanionic surfactant systems, tetradecyltrimethylammonium hydroxide ((TTA)OH)/lauric acid (LA)/H(2)O and cetyltrimethylammonium hydroxide ((CTA)OH)/LA/H(2)O, in the presence of deoxycholic acid (DeCA) were investigated and compared with the results of cholic acid (CA). Small-angle X-ray scattering, deuterium nuclear magnetic resonance, and rheological measurements were employed to monitor the phase structure and transition. The surface tension was used to investigate the surface activities of the bile acid/(TTA)OH and bile acid/(CTA)OH mixtures in dilute solutions. The results show that they have a minimum surface tension in a solution with excess cationic surfactant, and the critical micelle concentration decreases with an increase of the cationic surfactant chain length and hydrophobicity of the bile acids. At equimolar mixtures of DeCA and cationic surfactants, or DeCA being in excess, phase separation occurs with a large diameter of droplets in the upper phase and a small volume of viscous liquid in the bottom phase. Compared with CA systems, in the salt-free catanionic surfactant systems containing DeCA, phase transition from the birefringent L(alpha) phase to the L(1) phase occurs at a high molar fraction of DeCA, and the viscosity is higher at the same molar fraction of bile acid, indicating the significant influence of the molecule structures of bile acids despite only one hydroxyl group difference. Shear thickening is observed in the L(alpha) region, and a gradual evolvement of aggregates is predicted. Longer chain cationic surfactant can also increase the shear viscosity, which could be ascribed to the increase of the critical packing parameter, but with less influence on the phase transition.

NMR Structure of a Viral Peptide Inserted in Artificial Membranes: A VIEW ON THE EARLY STEPS OF THE BIRNAVIRUS ENTRY PROCESS

Nonenveloped virus must penetrate the cellular membrane to access the cytoplasm without the benefit of membrane fusion. For birnavirus, one of the peptides present in the virus capsid, pep46 for infectious bursal disease virus, is able to induce pores into membranes as an intermediate step of the birnavirus-penetration pathway. Using osmotic protection experiments, we demonstrate here that pep46 and its pore-forming N-terminal moiety (pep22) form pores of different diameters, 5-8 and 2-4 nm, respectively, showing that both pep46 moieties participate to pore formation. The solution structures of pep46, pep22, and pep24 (the pep46 C-terminal moiety) in different hydrophobic environments and micelles determined by (1)H NMR studies provide structural insights of the pep46 domain interaction. In CDCl(3)/CD(3)OH mixture and in dodecylphosphocholine micelles, the N-terminal domain of pep46 is structured in a long kinked helix, although the C terminus is structured in one or two helices depending upon the solvents used. We also show that the folding and the proline isomerization status of pep46 depend on the type of hydrophobic environment. NMR spectroscopy with labeled phospholipid micelles, differential scanning calorimetry, and plasmon waveguide resonance studies show the peptides lie parallel to the lipid-water interface, perturbing the fatty acid chain packing. All these data lead to a model in which the two domains of pep46 interact with the membrane to form pores.

Kinetic Control in the Chiral Recognition of Three-Bladed Propellers

The ion pair of the stereolabile C(3)-symmetric, i(+)o proton complex [1H](+) of diaza-macropentacycle 1 and the configurationally stable Delta-TRISPHAT ([Delta-3](-)) anion exists in the form of two diastereomers, namely, [Delta-(1.H)][Delta-3] and [Lambda-(1.H)][Delta-3], the ratio of which, in terms of diastereomeric excess (de) decreases in the order [D(8)]THF (28%)>CD(2)Cl(2) (22%)>CDCl(3) (20%)>[D(8)]toluene (16%)>C(6)D(6) (7%)>[D(6)]acetone (0%) at thermodynamic equilibrium. Except in the case of [D(6)]acetone, the latter is reached after a period of time that increases from 1 h ([D(8)]THF) to 24 h (CDCl(3)). Moreover, the initial value of the de of [1.H][Delta-3] in CDCl(3), before the thermodynamic equilibrium is reached, depends on the solvent in which the sample has been previously equilibrated (sample "history"). This property has been used to show that the crystals of [1.H][Delta-3] formed by slow evaporation of CH(2)Cl(2)/CH(3)OH mixtures had 100% de, which indicates that [1.H][Delta-3] has enjoyed a crystallization-induced asymmetric transformation. Structural studies in solution (NMR spectroscopy) and in the gas phase by calculations at the semiempirical PM6 level of theory suggest that the optically active anion is docked on the i(+) (endo) external side of the proton complex such that one of the aromatic rings of [Delta-3](-) is inserted into a groove of [1.H](+), a second aromatic ring being placed astride the outside i(+) pocket. Solvent polarity controls the thermodynamics of inversion of the [1.H](+) propeller. However, both polarity and basicity control its kinetics. Therefore, the rate-limiting steps correspond to the ion-pair separation/recombination and [1.H](+)/1 deprotonation/protonation processes, rather than the inversion of [1H](+), the latter being likely to take place in the deprotonated form (1).

Molecular Content and Structure of Aqueous Organic Nanodroplets from the Vapor−Liquid Nucleation Study of the Water/n-Nonane/1-Alcohol Series

Prompted by a previous finding of unusual mixing behavior for the critical clusters involved in the vapor-liquid nucleation of the ternary water/n-nonane/1-butanol mixture, atomistic simulations employing the AVUS-HR technique were carried out to extend such investigations to include both shorter and longer alcohols, namely, the water/n-nonane/CiH2i+1OH mixture with i = 2, 4, 6, and 8. It is clear from this extensive investigation that the miscibility between water and n-nonane can be further improved by increasing the chain length of the alcohol (surfactant). In fact, for the water/n-nonane/1-octanol mixture at an intermediate gas-phase activity composition, the nucleation can proceed via fully mixed critical nuclei containing a roughly equal amount of all three components, which is in contrast to the dominantly binary-like nucleation channels observed for such mixtures involving shorter alcohols. Structural analysis revealed that these mixed nuclei take on a multilayered structural motif of the core-shell (water-alcohol) type with n-nonane distributed outside, forming an additional layer, more or less uniformly, compared to the one-sided deposition found for systems involving shorter alcohols. This structure provides a microscopic origin for the enhanced miscibility of water with n-nonane observed in the presence of 1-alcohol. These results may also have important implications for atmospheric organic aerosols.

Synergistic enhancement of microbubble formation in ultrasound irradiated H2O–CH3OH mixtures probed by dynamic light scattering

This report investigates the formation of microbubbles in water–methanol mixtures upon ultrasound irradiation and its correlation with the yield of H2 obtained as a result of sonochemical splitting of water. The yield of hydrogen produced by sonochemical reaction is monitored at different compositions of water–methanol mixtures. The evidence for the formation of microbubbles upon ultrasound irradiation is obtained by the dynamic light scattering technique. Microbubble formation during ultrasound irradiation of water–methanol mixtures, their stability and size distribution, has been quantitatively estimated. The effect of composition of the water–methanol mixture and duration of irradiation on the extent of bubble formation has been inferred from the changes in the light scattering intensity and its time correlation function. Exceptional stability of microbubbles without any additives is observed at a certain composition of the water–methanol mixture (4 : 3, v/v). The extent of microbubbles formed in the mixture correlates well with the yield of hydrogen detected.

Vibrational nonequilibrium and electronic excitation in the reaction of hydrogen with oxygen behind a shock wave

A theoretical analysis of ignition and combustion processes in a hydrogen-oxygen mixture behind a shock wave is presented (1000 K ≤ T ≤ 2500 K; 2.0 atm ≥ P ≥ 0.3 atm). The experiments performed using stoichiometric mixtures with the detection of OH (2Σ+) and rich mixtures with the detection of OH (2Π) were interpreted in terms of a general kinetic approach. In this case, the apparent rate constant of the chain branching reaction H + O2 → O + OH was the only adjustable parameter. It was found that this rate constant increased with decreasing hydrogen content and exceeded equilibrium values. In this context, the mechanism of chain branching, which occurs through the formation of the vibrationally excited radical HO2(v), and the role of secondary vibrationally nonequilibrium O2 and O2(1Δ) molecules and the reaction H + O2(1Δ) → O + OH are discussed. New mechanisms of the formation and quenching of electronically excited OH(2Σ+) radicals, O(1 D) atoms, and O2(1Δ) molecules are considered. The results of a nonempirical (ab initio) analysis of molecular systems and the corresponding estimations of reaction rate constants were widely used.

Monomeric, tetrameric, and polymeric copper di-tert-butyl phosphate complexes containing pyridine ancillary ligands.

The reaction of di-tert-butyl phosphate (((t)BuO)(2)P(O)(OH), dtbp-H) with copper acetate in the presence of pyridine (py) and 2,4,6-trimethylpyridine (collidine) has been investigated. Copper acetate reacts with dtbp-H in a reaction medium containing pyridine, DMSO, THF, and CH(3)OH to yield a one-dimensional polymeric complex [Cu(dtbp)(2)(py)(2)(mu-OH(2))](n) (1) as blue hollow crystalline tubes. The copper atoms in 1 are octahedral and are surrounded by two terminal phosphate ligands, two pyridine molecules, and two bridging water molecules. The mu-OH(2) ligands that are present along the elongated Jahn-Teller axis are responsible for the formation of the one-dimensional polymeric structure. Recrystallization of 1 in a DMSO/THF/CH(3)OH mixture results in the reorganization of the polymer and its conversion to a more stable tetranuclear copper cluster [Cu(4)(mu(3)-OH)(2)(dtbp)(6)(py)(2)] (2) in about 60% yield. The molecular structure of 2 is made up of a tetranuclear core [Cu(4)(mu(3)-OH)(2)] which is surrounded by six bidentate bridging dtbp ligands. While two of the copper atoms are pentacoordinate with a tbp geometry, the other two copper atoms exhibit a pseudooctahedral geometry with five normal Cu-O bonds and an elongated Cu-O linkage. The pentacoordinate copper centers bear an axial pyridine ligand. The short Cu.Cu nonbonded distances in the tetranuclear core of 2 lead to magnetic ordering at low temperature with an antiferromagnetic coupling at approximately 20 K (J(P) = -44 cm(-1), J(c) = -66 cm(-1), g = 2.25, and rho = 0.8%). When the reaction between di-tert-butyl phosphate (dtbp-H) and copper acetate was carried out in the presence of collidine, large dark-blue crystals of monomeric copper complex [Cu(dtbp)(2)(collidine)(2)] (3) formed as the only product. A single-crystal X-ray diffraction study of 3 reveals a slightly distorted square-planar geometry around the copper atom. Thermogravimetric analysis of 1-3 revealed a facile decomposition of the coordinated ligands and dtbp to produce a copper phosphate material around 500 degrees C. An independent solid-state thermolysis of all the three complexes in bulk at 500-510 degrees C for 2 days produced copper pyrophosphate Cu(2)P(2)O(7) along with small quantities of Cu(PO(3))(2) as revealed by DR-UV spectroscopic and PXRD studies.

Parallel high-throughput accurate mass measurement using a nine-channel multiplexed electrospray liquid chromatography ultraviolet time-of-flight mass spectrometry system.

A nine-channel multiplexed electrospray (MUX) liquid chromatography ultraviolet time-of-flight mass spectrometry (LC/UV/TOFMS) system has been used to simultaneously measure accurate masses of eluting components from eight parallel gradient LC columns. Accuracies better than 5 and 10 ppm were achieved for 50 and 80% of samples, respectively, from a single batch analysis of ten plates (960 samples) of a Fmoc-Asp(OtBu)-OH and reserpine mixture. Combinatorial library compounds were analyzed using this parallel high-throughput system in both positive and negative modes to rigorously verify expected products and identify side products. A mass accuracy of 10 ppm root mean square (RMS) is routinely obtained for combinatorial library samples from this high-throughput accurate mass LC/MS system followed by automated data processing. This mass accuracy is critical in revealing combinatorial synthesis problems that would be missed by unit mass measurement.