Mole Of Compound Research Articles

Stability of highly supersaturated vanadium electrolyte solution and characterization of precipitated phases for vanadium redox flow battery

The vanadium redox flow battery (VRFB) has been receiving great attention in recent years as one of the most viable energy storage technologies for large-scale applications. However, higher concentrations of vanadium species are required in the H2O-H2SO4 electrolyte in order to improve the VRFB energy density. This might lead to unwanted precipitation of vanadium compounds, whose nature has not been accurately characterized yet. For this purpose, this study reports the preparation of V(II), V(III), V(IV) and V(V) supersaturated solutions in a 5 M H2SO4-H2O electrolyte by an electrolytic method, from the only vanadium sulfate compound commercially available (VOSO4). The precipitates obtained by ageing of the stirred solutions are representative of the solids that may form in a VRFB operated with such supersaturated solutions. The solid phases are identified using thermogravimetric analysis, X-ray diffraction and SEM. We report that dissolved V(II), V(III) and V(IV) species precipitate as crystals of VSO4, V2(SO4)3 and VOSO4 hydrates and not in their anhydrous form; conversely V(V) precipitates as an amorphous V2O5 oxide partially hydrated. The measured hydration degrees (respectively 1.5, 9, 3 and 0.26 mol of H2O per mol of compound) might significantly affect the overall engineering of VRFB operating with high vanadium concentrations.

Highly water-soluble ruthenium(II) terpyridine coordination compounds form stable adducts with blood-borne metal transporting proteins

Three coordination compounds of ruthenium(II), belonging to a recently synthesised series of water-soluble compounds of general formula mer-[Ru(L3)(N-N)Cl]Cl, where L3 = 4'-chloro-2,2':6',2″-terpyridine (Cl-tpy), N-N = ethylenediamine (en), 1,2-diaminocyclohexane (dach) or 2,2'-bipyridine (bpy), have shown strong binding to calf thymus DNA and moderate in vitro cytotoxicity towards cancer cell lines. Knowing that serum proteins play a crucial role in the transport and deactivation of ruthenium drugs, we have conducted a detailed study of their interactions with two major metal-transporting serum proteins, albumin and transferrin, and it is presented herein. Ruthenated protein adducts were formed with various concentrations of the three compounds and then separated from the unbound portions by ultrafiltration through 10kDa cut-off centrifugal filter units. The stoichiometry of binding was determined using inductively coupled plasma optical emission spectrometry. One mol of albumin bound up to 7, 8.5 and 1.5mol of compound 1 ([Ru(Cl-tpy)(en)Cl][Cl]), 2 ([Ru(Cl-tpy)(dach)Cl][Cl] and 3 ([Ru(Cl-tpy)(bpy)Cl][Cl]), respectively. One mol of transferrin bound up to 3, 3.5 and 0.4mol of 1, 2 and 3, respectively. The affinity of albumin and transferrin for the three ruthenium compounds was evaluated using fluorescence quenching. The binding constants for 1 and 2 lay within the range 104–105M−1, suggesting moderate-to-strong attachment to albumin. Both compounds showed much lower affinity for transferrin (102–103M−1). Compound 3 bound weakly to each studied protein. High resolution ESI qTOF mass spectra of albumin before and after binding of 1 revealed the high stoichiometry of binding. Although the binding of the compounds 1–3 to albumin and transferrin did not affect proteins’ secondary structure much, their tertiary structures underwent some alterations, as deduced from the circular dichroism study. Changes in the stability of albumin, after binding to compounds 1–3 were examined by differential scanning calorimetry.

First principles study of the ZrX2 (X = H, D and T) compounds

The Zr–H system is of particular importance for the solid state storage of hydrogen isotopes in the form of zirconium hydride. Here we report the structural, electronic, vibrational and thermodynamic properties of ZrH2, ZrD2 and ZrT2 using density functional theory (DFT). The structural optimization was carried out by the plane-wave based pseudo-potential method under the generalized gradient approximation (GGA) scheme. The electronic structure of the ZrH2 compound was illustrated explicitly. The vibrational, thermodynamic, and the effect of isotopes on ZrX2 (X = H, D, T) compounds were evaluated by the frozen phonon method. Both the Raman and infrared active vibrational modes of ZrX2 at Γ-point showed significant isotopic effect on ZrX2 compounds. For example, the phonon energy gap between optical and acoustic modes reduces for ZrT2 than ZrD2 and ZrH2. The formation energies of ZrX2 compounds, including the ZPE contributions, were estimated to be −143.68, −147.87 and −150.01 kJ/(mole of compound) for X = H, D and T, respectively.

Synthesis and investigation of the physicochemical properties of 2-(5-((theophylline-7'-yl)methyl)-4-phenyl-4H-1,2,4-triazole-3-ylthio)-acetic acid salts

Synthesis and investigation of the physicochemical properties of 2-(5-((theophylline-7'-yl)methyl)-4-phenyl-4H-1,2,4-triazole-3-ylthio)-acetic acid salts

Predicting total organic halide formation from drinking water chlorination using quantitative structure–property relationships

Chlorinating water which contains dissolved organic matter (DOM) produces disinfection byproducts, the majority of unknown structure. Hence, the total organic halide (TOX) measurement is used as a surrogate for toxic disinfection byproducts. This work derives a robust quantitative structure–property relationship (QSPR) for predicting the TOX formation potential of model compounds. Literature data for 49 compounds were used to train the QSPR in moles of chlorine per mole of compound (Cp) (mol-Cl/mol-Cp). The resulting QSPR has four descriptors, calibration of 0.72 and standard deviation of estimation of 0.43 mol-Cl/mol-Cp. Internal and external validation indicate that the QSPR has good predictive power and low bias (<1%). Applying this QSPR to predict TOX formation by DOM surrogates – tannic acid, two model fulvic acids and two agent-based model assemblages – gave a predicted TOX range of 136–184 µg-Cl/mg-C, consistent with experimental data for DOM, which ranged from 78 to 192 µg-Cl/mg-C. However, the limited structural variation in the training data may limit QSPR applicability; studies of more sulfur-containing compounds, heterocyclic compounds and high molecular weight compounds could lead to a more widely applicable QSPR.

Mn(CO)4{S2CNMe(CH2CO2H)}], a new water-soluble CO-releasing molecule

[Mn(CO)(4){S(2)CNMe(CH(2)CO(2)H)}], 1, is shown to be a CO releasing molecule providing at least three moles CO per mole of compound. The mechanism of CO loss is dissociative and reversible and was investigated using Gaussian 09 calculations. The reversible binding of CO results in a relatively stable solution of the compound, while in the presence of a CO receptor or a ligand to prevent the rebinding of CO, the CO is lost rapidly. The X-ray structure was determined.

Ce0.67Cr0.33O2.11: A New Low-Temperature O2 Evolution Material and H2 Generation Catalyst by Thermochemical Splitting of Water

Ce0.67Cr0.33O2.11 was synthesized by hydrothermal method using diethylenetriamine as complexing agent (Chem. Mater. 2008, 20, 7268). Ce0.67Cr0.33O2.11 being the only compound likes UO2+δ to have excess oxygen, it releases a large proportion of its lattice oxygen (0.167 M [O]/mole of compound) at relatively low temperature (465 °C) directly and it has been utilized for generation of H2 by thermo-splitting of water. An almost stoichiometric amount of H2 (0.152 M/Mole of compound) is generated at much lower temperature (65 °C). There is an almost comparable amount of oxygen release and hydrogen generation over this material at very low temperature compared to other CeO2−MOx (Mn, Fe, Cu, and Ni) mixed-oxide solid solutions (O2 evolution ≥1300 °C and H2 generation at 1000 °C). The reversible nature of oxygen release and intake of this material is attributed to its fluorite structure and coupling between the Ce4+/Ce3+ and Cr4+/6+/Cr3+ redox couples. Compound shows reversible oxygen release and intake by H2O absorption and subsequent hydrogen release to gain parent structure and hence this material can be utilized for generation of H2 at very low temperature by thermo-chemical splitting of water.

Hydrogen production from sodium borohydride for fuel cells in presence of electrical field

Sodium borohydride (NaBH4) reacts with water to produce 4 mol of hydrogen per mol of compound at room temperature. Under certain conditions, it was found that 6 mol of hydrogen per mol of sodium borohydride was produced in the presence of electrical field created by DC voltages, whereas 4 mol of hydrogen was produced in the presence of catalyst per mole of sodium borohydride. Electrical field created by alternative current with three different waves (sin, square and triangle type) increases the hydrolysis of sodium borohydride. It was found that hydrogen produced from sodium borohydride by applying an electrical field can be effectively used for both increasing the electrolysis of water and hydrolysis of sodium borohydride. The hydrolysis reaction was carried out at temperature of 20, 30, 40 and 60°C in the presence of electrical field created by AC voltages square wave. The experimental data were fitted to the kinetic models of zero-order, first-order and nth-order. The results indicate that the first-order and nth-order model give a reasonable description of the hydrogen generation rate at the temperature higher than 30°C. Reaction rate constant at different temperatures were determined from experimental data, and activation energy was found to be 50.20 and 52.28 kJ mol−1 for first-order and nth-order, respectively. Copyright © 2009 John Wiley & Sons, Ltd.

Characterization of Polyhalogenated Phenoxyphenols (Br/Cl-Predioxins) Formed during Aqueous Chlorination of Phenol in the Presence of Bromide Ion

Aqueous phenol solution with bromide ion was treated with sodium hypochlorite at 20°C under various experimental conditions. Changes in the composition and the concentration of the halogenated products in water were determined by gas chromatographic (GC) and GC-mass spectrometric (GC/MS) analyses of diethyl ether extracts. Phenol was shown to produce a variety of halogenated compounds, including polybrominated/chlorinated phenoxyphenols (PXPPs, Br/Cl-predioxins), having three to five halogen atoms, as byproducts in the chlorine-treated water. Production of these PXPPs is dependent on the number of equivalent chlorine atoms per mole of compound and on the reaction pH. These findings suggest that the chlorinetreatment of water contaminated with phenol and bromide ion leads to the formation of Br/Cl-predioxins, which are precursors of the highly toxic halogenated dibenzo-p-dioxins.

Reduction of aliphatic nitroesters and N-nitramines by Enterobacter cloacae PB2 pentaerythritol tetranitrate reductase

Enterobacter cloacae PB2 NADPH:pentaerythritol tetranitrate reductase (PETNR) performs the biodegradation of explosive organic nitrate esters via their reductive denitration. In order to understand the enzyme substrate specificity, we have examined the reactions of PETNR with organic nitrates (n = 15) and their nitrogen analogues, N-nitramines (n = 4). The reactions of these compounds with PETNR were accompanied by the release of 1-2 mol of nitrite per mole of compound, but were not accompanied by their redox cycling and superoxide formation. The reduction rate constants (k(cat)/K(m)) of inositol hexanitrate, diglycerol tetranitrate, erythritol tetranitrate, mannitol hexanitrate and xylitol pentanitrate were similar to those of the established PETNR substrates, PETN and glycerol trinitrate, whereas the reactivities of hexahydro-1,3,5-trinitro-1,3,5-triazine and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine were three orders of magnitude lower. The log k(cat)/K(m) value of the compounds increased with a decrease in the enthalpy of formation of the hydride adducts [DeltaH(f)(R-O-N(OH)O(-)) or DeltaH(f)(R(1),R(2) > N-N(OH)O(-))], and with an increase in their lipophilicity (octanol/water partition coefficient, log P(ow)), and did not depend on their van der Waals' volumes. Hydrophobic organic nitroesters and hydrophilic N-nitramines compete for the same binding site in the reduced enzyme form. The role of the hydrophobic interaction of PETNR with glycerol trinitrate was supported by the positive dependence of glycerol trinitrate reactivity on the solution ionic strength. The discrimination of nitroesters and N-nitramines according to their log P(ow) values seems to be a specific feature of the Old Yellow Enzyme family of flavoenzymes.

Mutagenicity of 2-[2-(acetylamino)-4-[bis(2-hydroxyethyl)amino]-5-methoxyphenyl]-5-amino-7-bromo-4-chloro-2 H-benzotriazole (PBTA-6) and benzo[ a]pyrene (BaP) in the gill and hepatopancreas of rpsL transgenic zebrafish

We examined the in vivo mutagenicity of 2-[2-(acetylamino)-4-[bis(2-hydroxyethyl)amino]-5-methoxyphenyl]-5-amino-7-bromo-4-chloro-2 H-benzotriazole (PBTA-6) and benzo[ a]pyrene (BaP) by using transgenic (Tg) zebrafish carrying the mutational target gene rpsL. PBTA-6 is one of the PBTA-type compounds that were recently identified in highly mutagenic river water in Japan. BaP is a well-known contaminant that is frequently found in polluted water. Both compounds are potent mutagens, as determined by using the Ames test employing S9 mix and Salmonella. Adult rpsL Tg zebrafish were exposed to 0, 7, or 10 mg/L PBTA-6 or 0, 1.5, or 3 mg/L BaP for 96 h in a water bath and the mutations in their gills and hepatopancreata were measured 2–4 weeks later. At 3 weeks after exposure, 3 mg/L BaP significantly increased the rpsL mutant frequency (MF) in the gill and hepatopancreas by 5- and 2.3-fold, respectively, as compared to control fish. Sequence analysis showed that BaP mainly induced G:C to T:A and G:C to C:G transversions, which is consistent with the known mutagenic effects of BaP. In contrast, despite its extremely high mutagenic potency in Salmonella strains, PBTA-6 did not significantly increase the MF in the zebrafish gill or hepatopancreas. Although PBTA-6 is 300 times more mutagenic than BaP in the Ames test [T. Watanabe, H. Nukaya, Y. Terao, Y. Takahashi, A. Tada, T. Takamura, H. Sawanishi, T. Ohe, T. Hirayama, T. Sugimura, K. Wakabayashi, Synthesis of 2-phenylbenzotriazole-type mutagens, PBTA-5 and PBTA-6, and their detection in river water from Japan, Mutat. Res. 498 (2001) 107–115], calculation of the mutagenicity per mole of compound indicated that PBTA-6 was 33- and <3.7-fold less mutagenic in the zebrafish gill and hepatopancreas, respectively, than BaP.

Characterization of Polyhalogenated 4-Methylphenol Dimers (Br/Cl-Predioxins) Formed during Aqueous Chlorination of 4-Methylphenol Solution in the Presence of Bromide Ion

Aqueous 4-methylphenol solution with bromide ion was treated with hypochlorite at 20°C under various experimental conditions. Changes in the composition of the halogenated products in water were determined by gas chromatographic (GC) and GC-mass spectrometric (GC/MS) analyses of diethyl ether extracts. 4-Methylphenol was shown to produce a variety of halogenated compounds, including polybrominated/chlorinated phenoxyphenols (Br/Cl-predioxins), having one to four halogen atoms, as by-products in the chlorine-treated water. Production of these predioxins is dependent on the number of equivalent of chlorine atoms per mole of compound and on the reaction pH. These results suggest that the chlorine treatment of water contaminated with 4-methylphenol and bromide ion leads to the formation of Br/Cl-predioxins, which are precursor of the highly toxic halogenated dibenzo-p-dioxins.

TLC Fractionation and Characterization of Ames Mutagenic Substances in Chlorine-treated 4-methylphenol Solution in the Presence of Bromide Ion

The diethyl ether extracts from aqueous 4-methylphenol solutions in the presence of bromide ion after treatment with chlorine were mutagenic to the Ames salmonella test strain TA100 in the absence of rat liver homogenate. Gas chromatography/mass spectrometry (GC/MS) showed the occurrence of halogenated products in the extracts: bromo-4-methylphenols, bromo-4-methylquinones and brominated 4-methylphenol dimers. The diethyl ether extracts were fractionated into several fractions by polyamide thin-layer chromatography (TLC) . The fractionated components were examined for mutagenicity by means of Ames assays, and were identified by GC/MS. TLC fraction of the extracts revealed that two components present in the extracts are mutagenic. GC/MS analysis indicated the presence of 2, 6-dibromo-4-hydroxy-4-methylcyclohexa-2, 5-lien-1-one (2, 6-dibromotolquinol) as the major mutagen and brominated 4-methylphenol dimers as minor mutagenic compounds in the chlorinated 4-methylphenol solutions containing bromide ion. Production of 2, 6-dibromotolquinol in water was found to be dependent on the equivalents of chlorine per mole of compound and the reaction pH.

AUTOMATED SCREENING WITH CONFIRMATION OF MECHANISM-BASED INACTIVATION OF CYP3A4, CYP2C9, CYP2C19, CYP2D6, AND CYP1A2 IN POOLED HUMAN LIVER MICROSOMES

A strategy is proposed to profile compounds for mechanism-based inactivation of CYP3A4, CYP2C19, CYP2C9, CYP2D6, and CYP1A2 based on an apparent partition ratio screen. Potent positives from the screen are confirmed by time- and concentration-dependent inactivation assays. Quasi-irreversible inhibitions are then differentiated from irreversible inactivations by oxidation with potassium ferricyanide and/or dialysis. The three-step screening procedure has been validated with acceptable accuracy and precision for detection and confirmation of mechanism-based inactivators in drug discovery. We report here the apparent partition ratios for 19 mechanism-based inactivators and four quasi-irreversible inhibitors obtained under the same experimental conditions. The apparent partition ratio screen was automated to provide throughput for determining structure-mechanism-based inactivation relationships. Information about reversibility can be used to assess potential toxicity mediated by covalent adducts, as well as the potential for pharmacokinetic drug-drug interactions. Direct comparison of known mechanism-based inactivators and quasi-irreversible inhibitors, based on our screening of apparent partition ratios, has identified ritonavir, mibefradil, and azamulin as highly effective mechanism-based inactivators; e.g., 1 mol of CYP3A4 was inactivated on turnover of about 2 mol of compound. Other mechanism-based inactivators we identified include bergamottin (CYP1A2 besides previously reported CYP3A4), troglitazone (CYP3A4), rosiglitazone (CYP3A4), and pioglitazone (CYP3A4). Comparison of the apparent partition ratios and inactivation clearance data for the three glitazones suggests that the chromane moiety on troglitazone contributes to its greater potency for mechanism-based inactivation.

Thermal investigations of dehydration of lanthanide(iii) 5-nitroanthranilates

The 5-nitro-2-anthranilates of lanthanum(III), samarium(III), terbium(III), erbium(III) and lutetium(III) were obtained as hydrates having 2.5 mol of water molecules per 1 mol of compound. The compounds are isostructural. The processes of dehydration and rehydration were investigated. The first step of dehydration does not cause the change of crystal structure. The entire dehydration gives anhydrous compounds with different structure than the structure of hydrates. However, the dehydration of La, Sm, Tb and Er is reversible - the rehydration process gives the complexes having the same crystal structure as the initial compounds. Only the anhydrous lutetium complex under the influence of moisture does not give the starting compound.

N-[(2-Sulfo)-9-fluorenylmethoxycarbonyl](3)-gentamicin C(1) is a long-acting prodrug derivative.

Most low-molecular-weight drugs are short-lived species in the circulatory system, being rapidly eliminated by glomerular filtration in the kidney. However, binding to human serum albumin (HSA) can slow clearance and prolong lifetime profile in vivo. In this study, we have engineered a gentamicin derivative with affinity to albumin by linking three (2-sulfo)-9-fluorenylmethoxycarbonyl (FMS) to three amino groups of gentamicin C(1). FMS(3)-gentamicin associates with HSA with a K(a) value of (1.31 +/- 0.2) x 10(5) M(-1). It has less than 1% the antibacterial potency of native gentamicin. Upon incubation at pH 8.5 and 37 degrees C, the FMS moieties from FMS(3)-gentamicin undergo slow hydrolysis (t(1/2) = 8.0 +/- 0.2 h), leading to a linear regeneration of the antibacterial potency with a t(1/2) value of 11 +/- 0.7 h. FMS(3)-gentamicin is a long-lived species in the rat circulatory system. Following a single subcutaneous or intravenous administration, it maintains a prolonged pharmacokinetic profile with a peak and a "through" concentration of immuno/antibacterial active gentamicin exceeding 4-5 times the duration obtained by administered native gentamicin. To sum up, an approach aimed at elongating the lifetime of low-molecular-weight drugs in vivo has been examined here with gentamicin. Two to three FMS per mole of compound are to be introduced to obtain an albumin associating affinity of K(d) = 7.6-9.2 microM and, hence, to significantly extend the drug's lifetime in situ following administration. By use of this technology, the loss of pharmacological potency with derivatization is of no consequence, since FMS moieties are hydrolyzed and activity is generated at physiological conditions.

A new hydrated sodium vanadium bronze as Li insertion compound

A sodium vanadium bronze hydrate, Na 0.33V 2O 5·1.3H 2O has been synthesized from reaction of phosphonic acid with vanadyl ions and sodium hydroxide in aqueous solution. The electrochemical Li insertion has been investigated in this layered structure characterized by a basal spacing of 10.84 Å. Its behaviour differs from that known for the sol–gel sodium-exchanged V 2O 5 xerogel and for the anhydrous monoclinic bronze. The presence of water does not hinder Li accommodation and two main reversible insertion steps are found at 3.1 V and 2.65 V for a maximum Li uptake of 1.65 lithium ion per mole of compound. Preliminary chronopotentiometric and cyclic voltammetric experiments indicate the potential interest of such a hydrated vanadium pentoxide bronze for reversible Li insertion reactions.

Transformation of Aqueous Phenolic Compounds in the Presence of Natural Organics and Chlorine into Ames Mutagenic Chloro-o-benzoquinones.

Some of chlorinated o-benzoquinones (o-BQs) have been shown to be mutagenic in Ames Salmonella assays. However, no study has been reported on the quantitative estimate of such compounds in aqueous solution. These mutagenic chemicals present in chlorine-treated aqueous solutions of mono- and dihydric phenols were, therefore, quantitatively determined by GC-MS as their phenazine derivatives.Chlorination of aqueous catechol solution was shown to produce a series of chlorinated compounds, including Chloro-o-BQs, and Chloro-hydroxy-o-BQ, in addition to o-BQ. No Chloro-o-BQs were found to be present in chlorine-treated resolcinol and hydroquinone solutions. After treatment with chlorine of aqueous chlorophenol solutions, dichloro-o-BQs were detected in these solutions. Production of chloro-o-BQs in water is dependent on the equivalents of chlorine per mole of compound, the reaction pH and the presence of lignin or humic acid. These results show that treatment with chlorine of water and wastewater contaminated with phenolic compounds leads to the production of mutagenic chlorinated o-BQs.

Long-chain-substituted uric acid and 5,6-diaminouracil derivatives as novel agents against free radical processes: synthesis and in vitro activity.

A new series of N-alkylated uric acids (2,6,8-purinetrione) and 5,6-diaminouracils (5,6-diamino-2,4-pyrimidinedione) were synthesized, and their activities against free radicals were evaluated. Long-chain derivatives of both series exhibited a large inhibitory activity against oxygen radical induced lipid peroxidation in bovine heart mitochondria (IC50 lower than 1 microM), compared to the reference antioxidants trolox C or alpha-tocopherol. This activity appeared related to (i) the ability of these compounds to reduce the stable radical 1,1-diphenyl-2-picrylhydrazyl and (ii) their lipophilicity estimated by log P determination. In order to study the scavenging mechanisms of diaminouracils and urate derivatives against lipid radicals, they were also tested against the azo-initiated peroxidation of either methyl linoleate in organic solvents or a liposomal suspension of dilinoleoylphosphatidylcholine. Urate derivatives reacted moderately with lipid radicals and were slowly consumed, significantly affecting the propagation of the peroxidation. Diaminouracils strongly reduced the propagation rate. They were quickly consumed and were able to deactivate about 1 mol of lipid radical per mole of compound in organic solvent. Dodecyl urates and decyl- and dodecyldiaminouracils were chosen for further in vitro investigation and in vivo evaluation.

Chemical Changes of Organic Compounds in Chlorinated Water. XIX. Production of Alkylpolychlorinated Phenoxyphenols (Predioxins) by Aqueous Chlorination of Alkylphenols.

Aqueous alkylphenol solutions were treated with chlorine at 20°C under various experimental conditions. Changes in the compositions of the chlorination products in water were determined by gas chromatographic (GC) and GC-mass spectrometric (GC-MS) analyses of diethyl ether extracts. Alkylphenols were shown to produce a variety of chlorinated compounds, including alkylpolychlorinated phenoxyphenols (predioxins), having one to five chlorine atoms, as by-products in chlorine-treated water. Production of some of these predioxins is dependent on the number of equivalents of chlorine per mol of compound and on the reaction pH. These results suggest that chlorine treatment of water contaminated with alkylphenols leads to the production of predioxins, which are precursors of the highly toxic chlorinated dibenzo-p-dioxins.