A comparison of worker exposure to inhalable and total dust, inorganic arsenic, and borates using two types of particulate sampling assemblies in a borate mining and processing facility

This study describes a comparison of worker exposure to total and inhalable dust, inorganic As, and borates using two types of particulate sampling assemblies as part of a comprehensive industrial hygiene evaluation in a borate mining and processing facility. Employees were segmented into similar exposure groups (SEG) based on work location within the facility, job classification, and type of chemical agent. Approximately 10% of the employees from each SEG wore two personal sampling devices simultaneously for the purpose of collecting total and inhalable particulate fractions using a closed face, 37-mm mixed cellulose ester matched-weight filters (MMW), and Institute of Occupational Medicine (IOM) sampling assembly. Sample results indicated that the IOM concentrations were consistently higher than the corresponding MMW concentrations for all three agents. An analysis was performed to investigate a relationship between MMW and IOM. The data revealed correlation coefficient values of 0.72, 0.82, and 0.84 for total dust (n = 197), inorganic As (n = 137), and borates (n = 194), respectively. These positive correlation coefficients indicate that the IOM and MMW measurements are consistent with each other, and can be used for predicting exposure levels. The total dust and borate large mean ratios should be considered in developing inhalable fraction-based regulatory standards.     

Heteroleptic lanthanide terphenyl/tris(pyrazolyl)borate compounds of ytterbium

The synthesis and structural characterization of the two novel unsolvated heteroleptic ytterbium compounds DanipYb(Tp^Me,Me)Cl (1) and DanipYb(Tp^Me,Me)CH₂SiMe₃ (2) by simple salt metathesis reaction is reported [Danip = 2,6-di(o-anisol)phenyl); Tp^Me,Me = hydrotris(3,5-dimethyl-pyrazolyl)borate]. In the molecular structure of 2 a flexible bonding mode of the donor-functionalized terphenylic ligand is observed.     

Carbon Incorporation and Anion Dynamics as Synergistic Drivers for Ultrafast Diffusion in Superionic LiCB11H12 and NaCB11H12

The disordered phases of LiCB₁₁H₁₂ and NaCB₁₁H₁₂ possess superb superionic conductivities that make them suitable as solid electrolytes. In these materials, cation diffusion correlates with high orientational mobilities of the CB₁₁H₁₂^? anions; however, the precise relationship has yet to be demonstrated. In this work, ab initio molecular dynamics and quasielastic neutron scattering are combined to probe anion reorientations and their mechanistic connection to cation mobility over a range of timescales and temperatures. It is found that anions do not rotate freely, but rather transition rapidly between orientations defined by the cation sublattice symmetry. The symmetry‐breaking carbon atom in CB₁₁H₁₂^? also plays a critical role by perturbing the energy landscape along the instantaneous orientation of the anion dipole, which couples fluctuations in the cation probability density directly to the anion motion. Anion reorientation rates exceed 3 × 10¹⁰ s^?1, suggesting the underlying energy landscape fluctuates dynamically on diffusion‐relevant timescales. Furthermore, carbon is found to modify the orientational preferences of the anions and aid rotational mobility, creating additional symmetry incompatibilities that inhibit ordering. The results suggest that synergy between the anion reorientational dynamics and the carbon‐modified cation–anion interaction accounts for the higher ionic conductivity in CB₁₁H₁₂^? salts compared with B₁₂H₁₂^2?.     

Low frequency of infertility among workers in a borate processing facility

In order to rule out the possibility of omitting some individuals in the study at field visits described in previous articles, either because of the reluctance of the subject or because of his appointment elsewhere, fertility and infertility states of borate workers of the Borax and Acid Plants in Bandirma, Balikesir are given. Balikesir is one of the four provinces with large borate deposits of Turkey, and Bandirma is 1 of its 19 districts. This county is relatively far away from borate deposits, and drinking water piped out through the springs has a boron amount between 0.10 and 0.82 ppm B. That the participants are occupationally exposed to the mineral in essence is therefore conceivable. At the first phase of the investigation, 191 workers were interviewed, as detailed previously. Among these, there were six infertiles of the primary type with a rate 3.1%. Boron-unrelated infertile couples among sibs were found to be 2.6–3.6%, and 3.2% for three-generation marriages—none being higher than those revealed in different sets of controls. In the second stage of work, computerized files of all workers of the facility and all employees of the general management sharing the same location were checked without an interview. Twenty-four subjects (3.4%) out of 712 workers were childless versus 2.7% among 108 employees, and 2.2% among 91 workers of a distantly located sulfuric acid plant of the same complex. The differences were not significant, and these recent findings support the conclusion already reached almost unambiguously that boron exposure at the present levels does not interfere with human reproduction.     

Assessment of fertility and infertility in boron-exposed Turkish subpopulations: 3. Evaluation of fertility among sibs and in "borate families"

As a part of a work to reveal the health effects of boron and its compounds, fertility and infertility states of sibs of probands, contacted and interviewed in the field, and of their spouses were given. The purposes were to prevent duplications seemingly inevitable in a relatively small community with prevailing consanguinity while analyzing marriages over respective generations and to reveal if there occurred an aggregation of infertile couples. Any family without offspring after about the second year of marriage was considered primary infertile as adopted throughout the study and such families were ascertained through the individual pedigree charts set up according to the instructions of the proband, he (she) himself (herself) being excluded. The rates of childless families of this type were 0.0–3.4% among male and 0.9–3.8% among female sibs of the participant, and 2.3–10.0% among male and 0.0–5.6% among female sibs of his (her) spouse with averages of 2.3% of 1589, 2.6% of 1589, 4.0% of 1314, and 3.3% of 1436 instances, respectively. The differences were insignificant and the rates were not different from those concerning probands themselves and that of a comparable segment of the Turkish population. “Borate families/kindreds” with two or more members engaged in the borate industry were also assessed in order to detect if there was a significant clustering of infertiles within the kindred. Although it was difficult to compare with a matched group, few couples were examples of familial concentration of infertility. These results provided further support that boron exposure does not affect human reproduction primarily and most probably secondarily. This work was partly presented to the 10th International Symposium on Trace Elements in Man and in Animal (TEMA-10), Evian, France, May 2–7, 1999.     

Synthesis and characterization of sterically hindered tris(pyrazolyl)borate Ni complexes

Addition of KTp^Ph2 to a solution of NiX₂ (X = Cl, Br, NO₃, OAc and acac) or NiBr(NO)(PPh₃)₂ in THF yields the structurally characterized series [NiCl(Hpz^Ph2)Tp^Ph2] (1) and [NiXTp^Ph2] (X = Br 2, NO 3, NO₃4, OAc 5 and acac 6) including the first example of a tris(pyrazolyl)borate nickel nitrosyl complex. IR spectroscopy confirms that all the Tp^Ph2 ligands are κ³ coordinated and that the NO ligand in 3 is linearly bound. Electronic spectra are consistent with four- or five-coordinate species in solution. NMR spectroscopic studies indicate that the complexes are paramagnetic, with the exception of 3. This is confirmed by magnetic susceptibility studies, which suggest that complexes 1, 2 and 4-6 are paramagnetic with two unpaired electrons. X-ray crystallographic studies of 5 reveal a distorted trigonal bipyramidal nickel centre with a symmetrically coordinated acetate ligand.     

Polyoxometalate cluster [V12B18O60H6] functionalized with the copper(II) bis-ethylenediamine complex

Three compounds based on the polyoxometalate building block [V₁₂B₁₈O₆₀H₆], (Na)₁₀[(H₂O)V₁₂B₁₈O₆₀H₆]·18H₂O (1), Na₈[Cu(en)₂]₂[V₁₂B₁₈O₆₀H₆](NO₃)₂·14.7H₂O (2), Na₇[Cu(en)₂]₂[V₁₂B₁₈O₆₀H₆](NO₃)·15.5H₂O (3), (en = ethylenediamine), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction analysis and TGA. Compound 1 consists of polyoxovanadium borate [V₁₂B₁₈O₆₀H₆] clusters which are surrounded by sodium countercations in octahedral sites, stabilized by electrostatic interactions with the oxygen atoms of both vanadium and boron centres. However, compounds 2 and 3 correspond to more complicated structures, constructed from the same polyoxometalate clusters, which are interconnected by [Cu(en)₂]²⁺ moieties via the terminal oxygen atoms of the polyoxoanions, generating one-dimensional structures. The functionalization of this polyoxovanadium borate cluster has been obtained by the use of [Cu(en)₂]²⁺ complex ions, thus demonstrating the capacity of the terminal oxygen atoms of the cluster to bind transition metal centres. The structural stability of the [V₁₂B₁₈O₆₀H₆] cluster permits the formation of functionalized polyoxometalate clusters, generating various crystalline lattices.     

Insights into the nature of Mo(V) species in solution: Modeling catalytic cycles for molybdenum enzymes

The tris(pyrazolyl)borate and related tripodal N-donor ligands originally developed by Trofimenko stabilize mononuclear compounds containing Mo^VIO₂, Mo^VIO, Mo^VO, and Mo^IVO units and effectively inhibit their polynucleation in organic solvents. Dioxo-Mo(VI) complexes of the type LMoO₂(SPh), where L = hydrotris(3,5-dimethylpyrazol-1-yl)borate (Tp^∗), hydrotris(3-isopropylpyrazol-1-yl)borate (Tp^iPr), and hydrotris(3,5-dimethyl-1,2,4-triazol-1-yl)borate (Tz) and related derivatives are the only model systems that mimic the complete reaction sequence of sulfite oxidase, in which oxygen from water is ultimately incorporated into product. The quasi-reversible, one-electron reduction of Tp^∗MoO₂(SPh) in acetonitrile exhibits a positive potential shift upon addition of a hydroxylic proton donor, and the magnitude of the shift correlates with the acidity of the proton donor. These reductions produce two Mo(V) species, [Tp^∗Mo^VO₂(SPh)]⁻ and Tp^∗Mo^VO(OH)(SPh), that are related by protonation. Measurement of the relative amounts of these two Mo(V) species by EPR spectroscopy enabled the pK_a of the Mo^V(OH) unit in acetonitrile to be determined and showed it to be several pK_a units smaller than that for water in acetonitrile. Similar electrochemical-EPR experiments for Tp^iPrMoO₂(SPh) indicated that the pK_a for its Mo^V(OH) unit was ∼1.7 units smaller than that for Tp^∗Mo^VO(OH)(SPh). Density functional theory calculations also predict a smaller pK_a for Tp^iPrMo^VO(OH)(SPh) compared to Tp^∗Mo^VO(OH)(SPh). Analysis of these results indicates that coupled electron-proton transfer (CEPT) is thermodynamically favored over the indirect process of metal reduction followed by protonation. The crystal structure of Tp^iPrMoO₂(SPh) is also presented.     

General Synthesis of Ultrathin Metal Borate Nanomeshes Enabled by 3D Bark‐Like N‐Doped Carbon for Electrocatalysis

Ultrathin nanomeshes perfectly inherit the integrated advantages of ultrathin 2D materials and porous nanostructures, which have shown their great application potential in catalysis and electronic devices. Here, the general synthesis of ultrathin metal borate (i.e., Co‐B_i, Ni‐B_i, and Fe‐B_i) nanomeshes is reported by capitalizing on 3D bark‐like N‐doped carbon (denoted BNC) as nanoreactors. Indeed, this strategy is straightforward, only comprising a one‐step reaction between metal cations and sodium borohydride without using templates. As nanoreactors, the BNC derived from biomass waste of lychee exocarp possesses distinctive advantages of low cost, fractured textures, porous nanostructures (surface area: 1915.5 m² g^?1), electronegative surface (zeta potential: ?43.4 mV), and superhydrophilicity for greatly facilitating the adsorption of metal cations with strong strength to effectively control the growth of 2D nanomeshes. The as‐synthesized Co‐B_i and Ru‐doped Co‐B_i (Ru‐Co‐B_i) nanomeshes exhibit excellent performance for the oxygen evolution reaction and hydrogen evolution reaction, respectively. Impressively, the water splitting device based on the Co‐B_i and Ru‐Co‐B_i nanomeshes can enable a current density of 10 mA cm^?2 at a small cell voltage of 1.53 V. Therefore, this work paves new avenues for the facile synthesis of ultrathin metal nanomeshes.     

Luminescent inorganic mixed borate phosphors materials for lighting

The need of new materials with desirable optical properties has become important in recent years. In particular, a need has emerged for compounds having better luminescence properties in various practical applications. The introduction of rare earth ions as activators improves the luminescence properties of the compounds considerably. Boron is one of the most abundant elements in nature. It readily combines with almost all other elements. In combination with oxygen; it forms borates comprised of various anions such as BO₃³⁻, B₂O₅⁴⁻, etc. Apart from these simple borates, several complex compositions exist involving mixed anions as well as double metal borates, due to the three-fold, or four-fold coordination of borate atoms. Borates intrinsically possesses characteristics that are advantageous for optical materials, which include a wide transparency range, large electronic band gap, good thermal and chemical stability, low preparative temperature, optical stability with good nonlinear characteristics, and an exceptionally high optical damage threshold. The unique crystal structure of borates determines their enhanced ultraviolet light transparency, good nonlinearity, and relatively high resistance against laser-induced damage. Some of these complex borates have interesting luminescence properties that are covered in this review. These include double borates containing rare earths RM₃(BO₃)₄, pentaborates LaMgB₅O₁₀, M₃R₂(BO₃)₄, where M is an alkaline earth, mixed anion borates such as aluminoborate SrAl₂B₂O₇, silicate-borates such as pekovite, SrB₂Si₂O₈, haloborates, M₂B₅O₉X, where M is an alkaline earth and X is a halogen, phosphate borates, and MBPO₅, where M is an alkaline earth. Phosphors based on these compositions find use in various applications such as fluorescence lamps, colour TVs, plasma display panels, high-intensity discharge lamps based on xenon, optically pumped solid-state lasers, eye-safe lasers, and X-ray imaging.