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The rates of oxidation of 3,5-di-tert-butyl catechol (3,5-DTBC) to 3,5-di-tert-butylbenzoquinone (3,5-DTBQ) by atmospheric dioxygen in the presence of five nickel(II)-polyoximate complexes as catalysts were measured at five different substrate-to-catalyst ratios. In all cases, saturation kinetics were observed at high substrate concentration. Analysis of the data using the Michaelis Menten model reveals rate constant values (kcat) ranging from 120 to 400 h− 1, which are comparable to results for other Ni(II)-polyoximate complexes in the literature. For the set of five catalysts examined in this work, those with the fewer number of coordinating groups on their polyoximate ligands showed the highest rates of reaction, while those with the higher number of coordinating groups showed the lowest rates of reaction. These results suggest that greater flexibility and possibly lower hindrance in the coordination sphere of the nickel centers of the catalysts enhance the rate of catalysis.

Beryllium exposure can cause a number of deleterious health effects, including beryllium sensitization and the potentially fatal chronic beryllium disease. Efficient methods for monitoring beryllium contamination in workplaces are valuable to help prevent dangerous exposures to this element. In this work, performance data on the extraction of beryllium from various size fractions of high-fired beryllium oxide (BeO) particles (from32 microm up to 212 microm) using dilute aqueous ammonium bifluoride (ABF) solution were obtained under various conditions. Beryllium concentrations were determined by fluorescence using a hydroxybenzoquinoline fluorophore. The effects of ABF concentration and volume, extraction temperature, sample tube types, and presence of filter or wipe media were examined. Three percent ABF extracts beryllium nearly twice as quickly as 1% ABF; extraction solution volume has minimal influence. Elevated temperatures increase the rate of extraction dramatically compared with room temperature extraction. Sample tubes with constricted tips yield poor extraction rates owing to the inability of the extraction medium to access the undissolved particles. The relative rates of extraction of Be from BeO of varying particle sizes were examined. Beryllium from BeO particles in fractions ranging from less than 32 microm up to 212 microm were subjected to various extraction schemes. The smallest BeO particles are extracted more quickly than the largest particles, although at 90 degrees C even the largest BeO particles reach nearly quantitative extraction within 4 hr in 3% ABF. Extraction from mixed cellulosic-ester filters, cellulosic surface-sampling filters, wetted cellulosic dust wipes, and cotton gloves yielded 90% or greater recoveries. Scanning electron microscopy of BeO particles, including partially dissolved particles, shows that dissolution in dilute ABF occurs not just on the exterior surface but also via accessing particles' interiors due to porosity of the BeO material. Comparison of dissolution kinetics data shows that as particle diameter approximately doubles, extraction time is increased by a factor of about 1.5, which is consistent with the influence of porosity on dissolution.

A standardized procedure for collecting dust samples from surfaces using a micro-vacuum sampling technique was evaluated. Experiments were carried out to investigate the collection efficiency of the vacuum sampling method described in ASTM Standard D7144, "Standard Practice for Collection of Surface Dust by Micro-Vacuum Sampling for Subsequent Metals Determination." Weighed masses ( approximately 5, approximately 10 and approximately 25 mg) of three NIST Standard Reference Materials (SRMs) were spiked onto surfaces of various substrates. The SRMs used were: (1) Powdered Lead-Based Paint; (2) Urban Particulate Matter; and (3) Trace Elements in Indoor Dust. Twelve different substrate materials were chosen to be representative of surfaces commonly encountered in occupational and/or indoor settings: (1) wood, (2) tile, (3) linoleum, (4) vinyl, (5) industrial carpet, (6) plush carpet, (7,8) concrete block (painted and unpainted), (9) car seat material, (10) denim, (11) steel, and (12) glass. Samples of SRMs originally spiked onto these surfaces were collected using the standardized micro-vacuum sampling procedure. Gravimetric analysis of material collected within preweighed Accucapinserts (housed within the samplers) was used to measure SRM recoveries. Recoveries ranged from 21.6% (+/- 10.4%, 95% confidence limit [CL]) for SRM 1579 from industrial carpet to 59.2% (+/- 11.0%, 95% CL) for SRM 1579 from glass. For most SRM/substrate combinations, recoveries ranged from approximately 25% to approximately 50%; variabilities differed appreciably. In general, SRM recoveries were higher from smooth and hard surfaces and lower from rough and porous surfaces. Material captured within collection nozzles attached to the sampler inlets was also weighed. A significant fraction of SRM originally spiked onto substrate surfaces was captured within collection nozzles. Percentages of SRMs captured within collection nozzles ranged from approximately 13% (+/- 4 - +/- 5%, 95% CLs) for SRMs 1579 and 2583 from industrial carpet to approximately 45% (+/- 7 - +/- 26%, 95% CLs) for SRM 1648 from glass, tile and steel. For some substrates, loose material from the substrate itself (i.e., substrate particles and fibers) was sometimes collected along with the SRM, both within Accucaps as well as collection nozzles. Co-collection of substrate material can bias results and contribute to sampling variability. The results of this work have provided performance data on the standardized micro-vacuum sampling procedure.

A series of nickel tris(oxime)amine complexes, including Ni(TRISOXH3)Br2 (2), [Ni(TRISOXH3)(MeOH)I]I (3), and [Ni(TRISOXH3)(H2O)2]F2 · 2H2O (4), was studied using modern density functional theory in combination with experimental methods (X-ray crystallography, Raman, and infrared spectroscopy). The series was compared to Ni(TRISOXH3)Cl2 (1), for which a detailed evaluation of theoretical models has been previously reported [R.M. Jones, M.J. Baldwin, J. Phys. Chem. 108 (2004) 3537]. The application of the theoretical model and the influence of changing the secondary ligands on nickel–TRISOXH3 interactions are evaluated. The crystal structures of 2, 3, and 4 show similar coordination geometries with some noted differences attributed to the different ligands. Unrestricted optimized geometry and frequency calculations were performed with the hybrid density functional B3LYP and split basis sets. Optimized geometries show small average absolute deviations for intraligand (0.016 A) and metal–ligand bonds (0.042 A) when compared to experimental crystal structures. The most intense vibrational modes of 2, 3, and 4 were assigned with the aid of a modified wavenumber linear scaling procedure, which resulted in 2- to 3-fold improvement in the agreement between experimental and theoretical wavenumbers. Derived linear scale functions for 1 can be successfully applied to theoretical frequencies of 2 and 3, but yield minimal improvement in the agreement between experimental and theoretical frequencies when applied to the frequencies of 4. Natural charge and unpaired spin distribution are evaluated for comparison of electronic influences of the varied ligands on metal–oxime interactions.

Two new ligands consisting of bis(oxime) amine units tethered by a bridge have been synthesized. Their nickel chloride and nickel nitrate complexes have also been synthesized and characterized by X-ray crystallography, FTIR, mass spectrometry, and elemental analysis. One of these ligands, L1 (N,N,N',N'-tetra(1-propan-2-onyl oxime)-diamino-m-xylene), is always dinucleating, while the other ligand, L2 (N,N,N',N'-tetra(1-propan-2-onyl-oxime)-1,3-diaminopropane), shows an unusual anion dependence on the nuclearity. When nickel chloride is used, the ligand acts in a dinucleating manner and coordinates two nickels; however, when nickel nitrate is used, the ligand acts in a monodentate fashion and coordinates only one nickel. Once the mononuclear complex is formed, it is not possible to add a second nickel if Ni(NO(3))(2) is used as the nickel source; it is possible, however, to add a second nickel if NiCl(2) is used as the nickel source. The dinuclear complex can be converted to the mononuclear one by either using silver nitrate to exchange the chloride anions for nitrates or by dissolving the complex in water. Ni(2)(L1)Cl(4)(DMF)(2).DMF: orthorhombic, P2(1)2(1)2(1), a = 12.2524(11) A, b = 16.6145(15) A, c = 20.1234(19) A, V = 4096.5(6) A(3), Z = 4. [Ni(2)(L2)Cl(4)(DMF)](2).2DMF: triclinic, P-1, a = 12.5347(5) A, b = 12.5403(5) A, c = 14.3504(6) A, alpha = 67.348(1) degrees , beta = 69.705(1) degrees , gamma = 81.549(1) degrees , V = 1952.25(14) A(3), Z = 1. Ni(L2).(NO(3))(2): monoclinic, P2(1)/n, a = 9.6738(3) A, b = 30.2229(9) A, c = 15.8238(5) A, beta = 97.995(1) degrees , V = 4581.4(2) A(3), Z = 8.

A new pendant-arm derivative of diaza-18-crown-6, containing two oxime donor groups, has been synthesized and incorporated into a polyvinyl chloride (PVC) membrane ion-selective electrode. The electrode shows selectivity for Ag+ ion, with a near Nernstian response. Pb2+, Cu2+, Hg2+, and Tl+ are major interfering ions, with Cd2+ having minor interference. The electrode shows no potentiometric response for the ions Mg2+, Al3+, K+, Ca2+, Ni2+, Fe3+, and La3+, and is responsive to H+ at pH

The ligand tris(1-propan-2-onyl oxime)amine (TRISOXH3) binds to zinc(II) acetate as a tridentate N3 donor, with a third oxime group remaining unbound and extending into the crystal lattice. The crystal structure shows a distorted trigonal bipyramidal geometry around the zinc center. An intramolecular hydrogen bonding interaction between a coordinated oxime donor and an oxygen of a bound acetate is observed. This structure is similar to that of a previously reported zinc(II) complex of a related bis(oxime)amine ligand. However, the structure of Zn(TRISOXH3)(OAc)2 is different in ligand coordination mode and metal coordination number from those of the previously reported complexes Ni(TRISOXH3)Cl2 or [Ni(TRISOXH3)(NO3)(H2O)]NO3.

A library of tripodal amine ligands with two oxime donor arms and a variable coordinating or noncoordinating third arm has been synthesized, including two chiral ligands based on l-phenylalanine. Their Ni(II) complexes have been synthesized and characterized by X-ray crystallography, UV-vis absorption, circular dichroism, and FTIR spectroscopy, mass spectrometry, and room-temperature magnetic susceptibility. At least one crystal structure is reported for all but one Ni/ligand combination. All show a six-coordinate pseudo-octahedral coordination geometry around the nickel center, with the bis(oxime)amine unit coordinating in a facial mode. Three distinct structure types are observed: (1) for tetradentate ligands, six-coordinate monomers are formed, with anions and/or solvent filling out the coordination sphere; (2) for tridentate ligands, six-coordinate monomers are formed with Ni(II)(NO(3))(2), with one monodentate and one bidentate nitrate filling the remaining coordination positions; (3) for tridentate ligands, six-coordinate, bis(mu-Cl) dimers are formed with Ni(II)Cl(2), with one terminal and two bridging chlorides filling the coordination sphere. The UV-vis absorption spectra of the complexes show that the value of 10 Dq varies according to the nature of the third arm of the ligand. The trend based on the third arm follows the order alkyl/arylamidecarboxylatealcoholpyridyloxime.

The active irritant in poison ivy, urushiol, has been extracted from native plants for the investigation into its metal-catalyzed oxidative decomposition. The decomposition of urushiol by atmospheric oxygen is promoted by complexes of Fe(III), including those of the ligands tris(2-methylpyridyl)amine (TPA) and nitriolotriacetate (NTA), and by simple Fe(III) salts. This is evidenced by the disappearance of the urushiol aromatic proton signal in the 1 H-NMR spectrum, as well as by identification of some of the oxygenation products by GC-MS. Analogous reactions using Zn(II) and Ni(II) complexes and salts show that substantial amounts of urushiol remain unreacted. This suggests that reactivity similar to that of catechol-dioxygenase enzymes may be the mechanism of the oxidative decomposition, and that simple coordination to transition metals may not be the mechanism by which urushiol is inactivated, as has been previously reported.

Inexpensive electrodes for the measurement of pH have been constructed using the ionophore tribenzylamine for sensing H+ concentrations. Both traditional liquid-membrane electrodes and coated-wire electrodes have been constructed and studied, and both exhibit linear, nearly Nernstian responses to changes in pH. Measurements of pH from these electrodes are accurate when compared to values obtained from simultaneous measurements using commercially available pH electrodes. The electrodes function well between pH values of 3 and 10. These electrodes are typically functional for two or more months before performance begins to degrade. Performing measurements in samples with abrasive solids, such as soils, also limits the working lifetimes of the electrodes. Students have successfully constructed these electrodes and used them in the measurement of soil pH levels.

The ligand tris(2-hydroxyiminopropyl)amine (Ox(3)H(3)) binds to nickel(II) in multiple protonation states. In the neutral state, the X-ray crystal structure of the monomeric complex [Ni(Ox(3)H(3))(NO(3))(H(2)O)](NO(3)).(H(2)O), 1, has six-coordinate pseudo-octahedral geometry, with binding of the amine and three oxime nitrogens, a nitrate, and a water. In the mono-deprotonated form, the X-ray crystal structure shows a dimer, [Ni(Ox(3)H(2))(CH(3)CN)](2)(ClO(4))(2), 2, which has bridging oximate groups and a Ni-Ni distance of 3.575 A. The fully deprotonated complex, 3, shows significantly low Ni(II) oxidation potentials at -390 and +165 mV (versus Fc(+)/Fc). Complex 3 shows reactivity when exposed to O(2), consuming multiple O(2) equivalents and turning from the purple 3 to a dark brown complex, 4. Complex 4 has an EPR spectrum consistent with Ni(III), but spin quantitation accounts for only about 10% of the total Ni, consistent with turnover of the Ni oxidation states. This Ni(II)/O(2) system oxidizes triphenylphosphine to its oxide, with incorporation of the isotopic label from O(2).

A series of five new alpha-hydroxy acid-containing chelates inspired by photoactive marine siderophores, along with their Fe(III) complexes, have been synthesized and characterized. These chelates, designated X-Sal-AHA, each contributes a bidentate salicylidene moiety (X-Sal, X = 5-NO(2), 3,5-diCl, H, 3,5-di-tert-butyl, or 3-OCH(3) on the phenolate ring) and a bidentate alpha-hydroxy acid moiety (AHA). The X-ray crystal structure of Na[Fe(3)(3,5-diCl-Sal-AHA)(3)(mu(3)-OCH(3))] shows an Fe(III) trimer with the triply deprotonated, trianionic ligands each spanning two Fe(III)'s that are bridged by the hydroxyl group of the ligand. Additionally, a mu(3)-methoxy anion caps the Fe(III)(3) face. Electrospray ionization mass spectra demonstrate that this structure is representative of the Fe(III) complexes of all five derivatives in methanol solution, with the exception of the X = 3,5-di-t-Bu derivative having a mu(3)-OH bridge rather than a methoxy bridge. Stability constants determined from reduction potentials range from 10(34) for the 5-NO(2) derivative to10(40) for the 3,5-di-tBu derivative. All five complexes are photoactive when irradiated by sunlight, with the relative rate of photolysis as monitored by Fe(II) transfer correlating with the Hammett sigma(+) parameter for the phenolate ring substituents.

Beryllium is widely used in industry for its unique properties; however, occupational exposure to beryllium particles can cause potentially fatal disease. Consequently, exposure limits for beryllium particles in air and action levels on surfaces have been established to reduce exposure risks for workers. Field-portable monitoring methods for beryllium are desired in order to facilitate on-site measurement of beryllium in the workplace, so that immediate action can be taken to protect human health. In this work, a standardized, portable fluorescence method for the determination of trace beryllium in workplace samples, i.e., air filters and dust wipes, was validated through intra- and inter-laboratory testing. The procedure entails extraction of beryllium in 1% ammonium bifluoride (NH(4)HF(2), aqueous), followed by fluorescence measurement of the complex formed between beryllium ion and hydroxybenzoquinoline sulfonate (HBQS). The method detection limit was estimated to be less than 0.02 microg Be per air filter or wipe sample, with a dynamic range up to greater than 10 microg. The overall method accuracy was shown to satisfy the accuracy criterion (Aor = +/-25%) for analytical methods promulgated by the US National Institute for Occupational Safety and Health (NIOSH). Interferences from numerous metals tested (in400-fold excess concentration compared to that of beryllium) were negligible or minimal. The procedure was shown to be effective for the dissolution and quantitative detection of beryllium extracted from refractory beryllium oxide particles. An American Society for Testing and Materials (ASTM) International voluntary consensus standard based on the methodology has recently been published.

The title compound, Ox3H3 or C9H18N4O3, adopts an open extended structure which does not restrict solvent accessibility or metallation reactivity. An intermolecular O—H⋯N hydrogen bond is observed.

Tris­[2-(benzoyl­amino)­ethyl]­amine [alternatively, N,N′,N′′-(nitrilo­tri­ethyl)­tri­benz­amide], C27H30N4O3, adopts a folded structure, forming a symmetrical cavity with an average depth of 7.3 A and width ranging from 4.1–4.4 A. The folded structure is a result of one intramolecular N—H⋯O hydrogen bond. A linear chain motif along the c axis best describes the extended intermolecular N—H⋯O hydrogen bonding.

An Environmentally Friendly, Cost-Effective Determination of Lead in Environmental Samples Using Anodic Stripping Voltammetry