Chlorinated Analogues Research Articles

Synthesis and Reactivity of Six-Membered Cyclic Diaryl λ3-Bromanes and λ3-Chloranes.

Despite the remarkable advancements in hypervalent iodine chemistry, exploration of bromine and chlorine analogues remains in its infancy due to their difficult synthesis. Herein, we introduce six-membered cyclic λ3-bromanes and λ3-chloranes. Through single-crystal X-ray structural analyses and conformational studies, we delineate the crucial bonding patterns pivotal for the thermodynamic stability of these compounds. Notably, these investigations reveal pronounced π-π stacking phenomena within the crystal lattice of hypercoordinated bromine(III) and chlorine(III) species. Their reactivity profile is explored as they are radical precursors or electrophilic reagents in metal-free intermolecular biaryl couplings, O- and S-arylations, and Cu(I)-promoted intramolecular biaryl couplings which is complementary to the known reactivity of five-membered bromanes and chloranes. Mechanistic insights are provided, elucidating the pathways governing their reactivity and underscoring the potential in organic synthesis.

Uptake, Elimination and Metabolism of Brominated Dibenzofurans in Mice.

Polybrominated dibenzofurans (PBDFs) are major brominated dioxins in the environment, but information on their bioaccumulation potential and toxicokinetics is limited. This study conducted oral exposure experiments with C57BL/6J mice to investigate the uptake ratios, distribution in the liver, plasma and brain, metabolism, and elimination kinetics of four bromine/chlorine-substituted dibenzofurans (TrBDF: 2,3,8-tribromo, TeBDF: 2,3,7,8-tetrabromo, PeBDF: 1,2,3,7,8-pentabromo, TrBCDF: 2,3,7-tribromo-8-chloro) in comparison with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The hepatic uptake ratios of 2,3,7,8-substituted dibenzofurans were lower than that of TCDD (up to 84% of the administered doses) and decreased with the number of Br substitutions (42%, 33%, and 29% for TrBCDF, TeBDF, and PeBDF, respectively). The brain uptake ratios of these dibenzofurans were less than 0.05%, and the plasma-to-brain transfer ratio also decreased with the Br number. All 2,3,7,8-substituted compounds were eliminated from the liver following first-order kinetics, with half-times in the order of TrBCDF (5.6 days) < TeBDF (8.8 days) ≈ TCDD (8.7 days) < PeBDF (13 days). The non-2,3,7,8-substituted TrBDF was poorly retained in the liver (<0.01% of the dose at 1 day) and rapidly eliminated following two-phase kinetics. All dibenzofurans were metabolised into monohydroxylated products in the liver, but the contribution of this metabolic pathway to hepatic elimination was only significant for TrBDF. As the toxic effects of dioxin-like compounds are influenced by their biological persistence, the slow elimination of TrBCDF, TeBDF, and PeBDF observed in this study suggests that exposure risk of brominated dibenzofurans may be underestimated using the toxic equivalency factors of the less persistent chlorinated analogues.

Electronic Structures of an Annulated meso-Tetraphenylchlorin and a Related Chlorin Analogue Incorporating an 8-Membered Ring through MCD Spectroscopy and DFT Calculations.

Herein, we compare the electronic structures of the metal-free and nickel(II) derivatives of an annulated meso-tetraphenyldihydroxychlorin with those of the (metallo)chlorin analogues derived by pyrroline β,β'-ring cleavage of the annulated (metallo)chlorins. These (metallo)chlorin analogues incorporate 8-membered heterocycles in place of the pyrroline, carry oxo-functionalities on the former pyrroline β-carbon atoms, and were previously shown to possess drastically ruffled (twisted) nonplanar conformations. The magnetic circular dichroism spectra of all chromophores investigated feature chlorin-like UV-vis spectra and correspondingly reversed (positive-to-negative in ascending energy) sign sequences in the Q-band region, indicative of ΔHOMO < ΔLUMO relationships. Density functional theory (DFT) calculations indicate that the HOMOs in all compounds are a1u-type molecular orbitals (in traditional for the porphyrin spectroscopy D4h point group). Time-dependent DFT calculations correlate well with the experimental spectra and indicate that Gouterman's four-orbital model can be applied to these chromophores. This work highlights to which degree synthetic chlorin analogues can deviate from the structural parameters of natural chlorins without losing their electronic chlorin characteristics.

Weak hydrogen bonding to halogens and chirality communication in propanols: Raman and microwave spectroscopy benchmark theory.

Constitutional and conformational isomers of bromopropanol are vibrationally and rotationally characterised with parallels drawn to the structural chlorine analogues. A previous microwave spectroscopic study of the chloropropanols is re-examined and all systems are explored by Raman jet spectroscopy. For bromine, the entire nuclear quadrupole coupling tensors are accurately determined and compared to their chlorine counterparts. Tensor asymmetry parameters are determined and linked with the hydrogen bond strength as indicated by the downshift of the OH-stretching frequency. The spectroscopic constants derived from the observed transitions are used as benchmarks for a large variety of electronic structure methods followed by harmonic and anharmonic rovibrational treatments. The CCSD(T) electronic structure calculations provide the best performance, in particular once anharmonic and relativistic corrections are applied or implied. Standard DFT approaches vary substantially with respect to their systematic error cancellation across the investigated species, and cost-effective compromises for the different observables are proposed.

Comparative formation of chlorinated and brominated disinfection byproducts from chlorination and bromination of amino acids

Amino acids are the main components of dissolved organic nitrogen in algal- and wastewater-impacted waters, which can react with chlorine to form toxic halogenated disinfection by-products (DBPs) in the disinfection process. In the presence of bromide, the reaction between amino acids and secondarily formed hypobromous acid can lead to the formation of brominated DBPs that are more toxic than chlorinated analogues. This study compares the formation of regulated and unregulated DBPs during chlorination and bromination of representative amino acids (AAs) (e.g., aspartic acid, asparagine, tryptophan, tyrosine, and histidine). In general, concentrations of brominated DBPs (trihalomethanes, haloacetonitriles, and haloacetamides, 24.9–5835.0 nM) during bromination were higher than their chlorinated analogues (9.3–3235.3 nM) during chlorination. This indicates the greater efficacy of bromine as a halogenating agent. However, the formation of chlorinated haloacetic acids during chlorination was higher than the corresponding brominated DBPs from bromination. It is likely that an oxidation pathway is required for the formation of haloacetic acids and chlorine is a stronger oxidant than bromine. Moreover, chlorine forms higher levels of haloacetaldehydes (74.4–1077.8 nM) from amino acids than bromine (1.0–480.2 nM) owing to the instability of brominated species. The DBP formation yields depend on the types of functional groups in the side chain of AAs. Eight intermediates resulting from chlorination/bromination of tyrosine were identified by triple quadrupole mass spectrometer, including N-chlorinated/brominated tyrosine, 3-chloro/bromo-tyrosine, and 3,5-dichloro/dibromo-tyrosine. These findings provided new insights into the DBP formation during the chlorination of algal- and wastewater-impacted waters with elevated bromide.

Strong spin frustration and magnetism in kagomé antiferromagnets LnCu3(OH)6Br3 (Ln = Nd, Sm, and Eu)

To study the effects of lanthanide ions on the geometrically frustrated antiferromagnets and their magnetic properties, we grew high-quality single crystals of LnCu3(OH)6Br3 (Ln = Nd, Sm, and Eu) by hydrothermal method and studied their crystal structures and magnetic properties. The refinements of the crystal structure referred to the powder x-ray diffraction data show that LnCu3(OH)6Br3 adopt a Kapellasite-type layer structure, which is isostructural to their chlorine analogue. Magnetic susceptibilities demonstrate that LnCu3(OH)6Br3 have strong antiferromagnetic coupling and a pronounced magnetic frustration effect. Magnetization measurements indicate canted antiferromagnetic ordering of Cu2+ ions around 16 K within the kagomé plane and weak ferromagnetic coupling. Moreover, shoulder-like anomalies in specific heat around 16 K could be a signature of emergent of magnetic ordering. The low-temperature negative magnetization and specific heat of LnCu3(OH)6Br3 (Ln = Nd, Sm, and Eu) indicate that Ln 3+ ions induce more exotic magnetic ground state properties.

Volatile Additive Strategy Triggering 17.48% Efficient Post‐Treatment‐Free Organic Solar Cells

Active layer morphology is critical to determine the photovoltaic performance of organic solar cells (OSCs), and additive‐assisted morphology optimization is one of the most widely used strategies to fine tune the donor–acceptor network in the active layer. However, the postprocessing procedures and additive residues require additional efforts to maintain the device performance. Herein, a low‐cost, simple structural design and volatile solid additive 2,5‐diiodothiophene is demonstrated to effectively optimize the active layer morphology and prompt the photoelectric conversion efficiency (PCE) of OSCs without any post‐treatment, outperforming the devices fabricated with the prototypical volatile additive 1,4‐diiodobenzene. The 2,5‐diiodothiophene (DIT)‐optimized PM6:Y6 binary OSCs obtain a PCE of 17.48%, accompanied with reduced trap‐assisted charge recombination and balanced charge carrier mobility. In addition, we notice that the bromide and chlorine analogues of DIT can enhance the device performance to a certain extent as well. The findings suggest that the post‐treatment‐free nature of the thiophene‐based processing additives are promising candidates for tuning the active layer morphology, providing simple processability for large‐scale fabrication of OSCs.

Variation in the formation characteristics of PBDD/F, brominated PAH, and PBDE congeners along the secondary copper smelting processes

Simultaneous determination of 58 congeners of polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs), brominated polycyclic aromatic hydrocarbons (Br-PAHs), and polybrominated diphenyl ethers (PBDEs) from multiple stages of industrial-scale secondary copper smelting plants was conducted with the aim of understanding their variations and control. In addition to the historical manufacture of PBDEs as brominated flame retardants, this study confirmed that PBDEs can be unintentionally produced and released from the secondary copper industry. The average mass emission factors of PBDD/Fs, PBDEs, and Br-PAHs from different sources were 10.0, 5.21 × 103, and 7.24 × 103 μg t−1, respectively. Therefore, the emission of brominated persistent organic pollutants (POPs) in the secondary copper industry should be of concern. The concentration of brominated POPs increased from the gas cooling stage to stack outlet due to the possible “memory effect” and the regenerated POPs were mainly low-brominated homologs. A comparison of brominated POPs with corresponding chlorinated analogs in the same process indicated that the formation pathway of Br-PAHs was consistent with that of chlorinated PAHs. However, unlike chlorinated dioxins and furans, PBDD/Fs can also be formed from PBDEs as precursors, leading to obvious increases in highly brominated furans. Therefore, inhibiting the unintentional formation of PBDEs is important for controlling brominated POPs emissions.

Crystal structure of cis-7,8-dihy-droxy-5,10,15,20-tetra-phenyl-chlorin and its zinc(II)-ethyl-enedi-amine complex.

The title chlorin, 2PhH2 , hydrogen-bonded to di-methyl-amino-pyridine (DMAP), C44H32N4O2·C7H10N2, and its corresponding zinc(II) complex, 2PhZn, axially coordinated to ethyl-enedi-amine (EDA), [Zn(C44H30N4O2)]·C2H8N2, were isolated and crystallized by adventitious reduction of the corresponding osmate esters by DMAP and EDA, respectively. Known since 1996 and, inter alia, used for the preparation of a wide range of (planar and non-planar) chlorin analogues (so-called pyrrole-modified porphyrins), their conformational analyses in the solid state are important benchmarks. Both macrocycles are only modestly distorted from planarity and both are slightly more non-planar than the corresponding dimeth-oxy-derivative, but less planar than a free-base meso-penta-fluoro-phenyl-based osmate ester. NSD analyses provide qu-anti-tative and qualitative analyses of the distortion modes. One origin of the non-planarity is presumably the avoidance of the eclipsed configuration of the two vic-cis diols on the pyrroline moiety; the resulting deformation of the pyrroline translates in some cases into the macrocycle. The structure of 2PhH2 features voids making up ca 26% of the unit-cell volume filled with highly disordered solvate mol-ecules (chloro-form and hexa-nes). 2PhZn crystallized with a 13.6 (4)% occupied solvate methanol mol-ecule.

Cytotoxicity and Antibacterial Evaluation of O-Alkylated/Acylated Quinazolin-4-one Schiff Bases.

A series of quinazolin-4-one Schiff bases were synthesized and tested in vitro for their cytotoxicity against two cancerous cell lines (MCF-7, Caco-2) and a human embryonic cell line (HEK-293) including their antibacterial evaluation against two Gram-positive and four Gram-negative bacterial strains. Most of the quinazoline-Schiff bases exhibited potent cytotoxicity against Caco-2. 3-[(Z)-({4-[(But-2-yn-1-yl)oxy]phenyl}methylidene)amino]-2-methylquinazolin-4(3H)-one (6f) with the O-butyne functional group displayed three-fold higher cytotoxic activity (IC50 =376.8 μM) as compared to 5-fluorouracil (5-FU; IC50 =1086.1 μM). However, all compounds were found to be toxic to HEK-293, except for 3-[(Z)-({4-[(2,4-difluorophenyl)methoxy]phenyl}methylidene)amino]-2-methylquinazolin-4(3H)-one (6h) that showed ∼three-fold lower toxicity and higher selectivity index than 5-FU. Structure-activity relationship (SAR) analysis revealed that O-alkylation generally increased the anticancer activity and selectivity of quinazoline-4-one Schiff bases toward Caco-2 cells. The fluorinated Schiff-base generally exhibited even more significant cytotoxic activity compared to their chlorine analogs. Surprisingly, none of the quinazoline-4-one Schiff bases displayed encouraging antibacterial activity against the bacterial strains investigated. Most of the compounds were predicted to show compliance with the Lipinski parameters and ADMET profiles, indicating their drug-like properties.

The Quantitative Influence of Coordinated Halogen Atoms on the Catalytic Performance of Bisiminoacenaphthylnickel Complexes in Ethylene Polymerization.

In experiments, nickel bromine complexes usually show a better catalytic performance in ethylene polymerization compared to their nickel chlorine analogues. Therefore, the present modeling study has been performed to investigate the effect of coordinated halogen atoms on the catalytic performances of two bisiminoacenaphthyl nickel systems, namely, Ni-Br and Ni-Cl. By using the multiple linear regression analysis (MLRA), the catalytic activity can be well predicted by the descriptors of effective net charge (Qeff ) and bite angle (β), with correlation coefficient R2 values over 0.91. Meanwhile, the molecular weights of polyethylene are predicted by the descriptors of Qeff and open cone angle (θ). The calculated contributions of each descriptor show that the electronic effect is the predominant factor in Ni-Br system, while the steric effect becomes the dominant factor in Ni-Cl system. The different determined effect is expected to the main reason for the different catalytic performance between two Ni systems.

Formation and control of C- and N-DBPs during disinfection of filter backwash and sedimentation sludge water in drinking water treatment

Drinking water treatment plants (DWTPs) produce filter backwash water (FBW) and sedimentation sludge water (SSW) that may be partially recycled to the head of DWTPs. The impacts of key disinfection conditions, water quality parameters (e.g., disinfection times, disinfectant types and doses, and pH values), and bromide concentration on controlling the formation of trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), and haloacetamides (HAMs) during disinfection of FBW and SSW were investigated. Concentrations of most disinfection byproducts (DBPs) and associated calculated toxicity increased with extended chlorination for both FBW and SSW. During chlorination of both FBW and SSW, elevated chlorine doses significantly increased THM yields per unit dissolved organic carbon (DOC), but decreased HAN and HAM yields, with minimum effect on HAA yields. Chloramine disinfection effectively inhibited C-DBP formation but promoted N-DBPs yields, which increased with chloramine dose. Calculated toxicities after chloramination increased with chloramine dose, which was opposite to the trend found after free chlorine addition. An examination of pH effects demonstrated that C-DBPs were more readily generated at alkaline pH (pH=8), while acidic conditions (pH=6) favored N-DBP formation. Total DBP concentrations increased at higher pH levels, but calculated DBP toxicity deceased due to lower HAN and HAM concentrations. Addition of bromide markedly increased bromo-THM and bromo-HAN formation, which are more cytotoxic than chlorinated analogues, but had little impact on the formation of HAAs and HAMs. Bromide incorporation factors (BIFs) for THMs and HANs from both water samples all significantly increased as bromide concentrations increased. Overall, high bromide concentrations increased the calculated toxicity values in FBW and SSW after chlorination. Therefore, while currently challenging, technologies capable of removing bromide should be explored as part of a strategy towards controlling cumulative toxicity burden (i.e., hazard) while simultaneously lowering individual DBP concentrations (i.e., exposure) to manage DBP risks in drinking water.

Quantum spin liquid candidate YCu3(OH)6Br2[Brx(OH)1−x] (x ≈ 0.51): With an almost perfect kagomé layer

Herbertsmithite ZnCu3(OH)6Cl2 was initially proposed to have a “perfect” model for the S = 1/2 kagomé antiferromagnet, but further investigations have revealed its intrinsic shortcomings arising from serious intersite mixing between Zn2+ and Cu2+ ions. Another system YCu3(OH)6Cl3 with a more perfect kagomé lattice has been developed to minimize intersite mixing, but is adversely affected by common parasitic intergrowth inclusions and surface coating of Cu2(OH)3Cl, which led to ambiguous and contradictory magnetic data. Herein we report a new bromine compound YCu3(OH)6Br2[Brx(OH)1−x] (x ≈ 0.51), which not only inherits the almost perfect kagomé lattice from its chlorine analogue but also eludes the impurities from either inclusion or surface coating, resulting in high quality pure single crystals. Single crystal X-ray diffraction data of the title compound does not support the superstructure model suggested for its chlorine analogue but suggests an incommensurate structure. Magnetic measurements demonstrate that the title compound features a strong antiferromagnetic (AFM) interaction with θcw = −74 K at low temperature and no long-range magnetic order down to 2 K. These results suggest that the title compound is a new promising quantum spin liquid candidate, successfully overcoming the above-mentioned shortcomings of herbertsmithite, kapellasite and YCu3(OH)6Cl3.

Syntheses of Dioxygenyl Salts by Photochemical Reactions in Liquid Anhydrous Hydrogen Fluoride: X-ray Crystal Structures of α- and β-O2Sn2F9, O2Sn2F9·0.9HF, O2GeF5·HF, and O2[Hg(HF)]4(SbF6)9.

By treating gaseous, liquid, or solid fluorides with UV-photolyzed O2/F2 mixtures and by treating solid oxides with UV-photolyzed F2 (or O2/F2 mixtures) in liquid anhydrous HF at ambient temperature, we investigated the possibility of the preparation of O2MIIIF4 (M = B, Fe, Co, Ag), O2MIVF5 (M = Ti, Sn, Pb), (O2)2MIVF6 (M = Ti, Ge, Sn, Pb, Pd, Ni, Mn), O2MIV2F9 (M = Sn), O2MVF6 (M = As, Sb, Au, Pt), O2MV2F11 (M = Pt), O2MVIF7 (M = Se), (O2)2MVIF8 (M = Mo, W), and O2MVIIF8 (M = I). The approach has been successful in the case of previously known O2BF4, O2MF6 (M = As, Sb, Au; Pt), O2GeF5, and (O2)2(Ti7F30). Novel compounds O2GeF5·HF, α-O2Sn2F9 (1-D), and the HF-solvated and nonsolvated forms of β-O2Sn2F9 (2-D) were synthesized and their crystal structures determined using single-crystal X-ray diffraction. The crystal structures of all of these materials arise from the condensation of octahedral MF6 (M = Ge, Sn) units. The anion in the crystal structure of O2GeF5·HF is comprised of infinite ([GeF5]−)∞ chains of GeF6 octahedra that share common vertices. The HF molecules and O2+ cations are located between the chains. The crystal structure of α-O2SnF9 (1-D) is constructed from [O2]+ cations and polymeric ([Sn2F9]−)∞ anions which appear as two parallel infinite chains comprised of SnF6 units, where each SnF6 unit of one chain is connected to a SnF6 unit of the second chain through a shared fluorine vertex. The single-crystal structure determination of [O2][Sn2F9]·0.9HF reveals that it is comprised of two-dimensional ([Sn2F9]−)∞ grids with [O2]+ cations and HF molecules located between them. The 2-D grids have a wavelike conformation. The ([Sn2F9]−)∞ layer contains both six- and seven-coordinated Sn(IV) atoms that are interconnected by bridging fluorine atoms. A new, more complex [O2]+ salt, O2[Hg(HF)]4[SbF6]9, was prepared. In its crystal structure, the Hg atoms bridge to SbF6 units to form a 3-D framework. The O2+ cations are located inside the voids while the HF molecules are bound to Hg atoms through the F atom. Attempts to prepare several chlorine analogues of O2+ fluorine salts (i.e., O2TiCl5 and O2MCl6 (M = Nb, Sb)) failed.

The submillimeter-wave spectrum of F2SO ([formula omitted]A′)

The sub-millimeter/THz spectrum of thionyl fluoride, F2SO (X∼1A′), has been recorded for the first time using direct absorption techniques in the frequency range 286–508 GHz. This work considerably expands the previous measurements for F2SO, which were all below 77 GHz. F2SO was synthesized in the gas phase by the reaction of pure SF6 with residual H2O vapor either in a DC discharge or a heated reaction chamber. Over two-hundred fifty transitions frequencies were recorded for this molecule in the range J = 16 to J = 30, with Kc = 0–28, each with a c-type pattern. The data were analyzed with an asymmetric top Hamiltonian in a combined fit with previous microwave measurements, and highly accurate rotational and centrifugal distortion constants were determined, including sextic distortion terms that were previously undefined. These parameters are the most accurate set of spectroscopic constants to date for F2SO. An rm(1) structure was determined for F2SO, which appears to show less steric hindrance than its chlorine analog, Cl2SO. F2SO is an important degradation product of SF6, and its pure rotational spectrum is of interest for environmental studies.

Conformational Landscapes of Metal(II) Porphyrinato, Chlorinato, and Morpholinochlorinato Complexes.

The macrocycle conformation of [meso-tetraarylporphyrinato]metal complexes is metal-dependent. Furthermore, hydroporphyrins and some of their analogues are known to be more conformationally flexible than the parent porphyrins, but the extent to which this is reflected in their metal-dependent conformations was much less studied. meso-Tetraarylmorpholinochlorins are intrinsically nonplanar chlorin analogues in which the five-membered pyrroline moiety was replaced by a six-membered morpholine moiety. The metal complexes (M = Ni2+, Cu2+, Zn2+, Pd2+, Ag2+) of meso-aryl-2,3-dimethoxychlorins and meso-arylmorpholinochlorins were prepared. Their conformations were determined using X-ray crystal structure diffractometry and compared against those of their free bases, as well as against the conformations of the corresponding metalloporphyrins. Out-of-plane displacement plots visualized and quantified the conformational changes upon stepwise conversion of a pyrrole moiety to a dimethoxypyrroline moiety and to a dialkoxymorpholine moiety, respectively. The generally nonplanar macrocycle conformations were found to be central-metal-dependent, with the smaller ions showing more nonplanar conformations and with the metallomorpholinochlorins generally showing a much larger conformational range than the corresponding metallochlorins, which, in turn, were more nonplanar than the corresponding porphyrins. This attests to the larger conformational flexibility of the morpholinochlorin macrocycle compared to that of a chlorin or even a porphyrin macrocycle. The degree of nonplanarity affects the electronic structure of the metal complexes, as can also be seen in a comparison of their UV-vis spectra. We thus further define the conformational and electronic effects governing pyrrole-modified porphyrins.

Stable Chloro- and Bromoxenate Cage Anions; [X3(XeO3)3]3- and [X4(XeO3)4]4- (X = Cl or Br).

The number of isolable compounds which contain different noble-gas-element bonds is limited for xenon and even more so for krypton. Examples of Xe-Cl bonds are rare, and prior to this work, no Xe-Br bonded compound had been isolated in macroscopic quantities. The syntheses, isolation, and characterization of the first compounds to contain Xe-Br bonds and their chlorine analogues are described in the present work. The reactions of XeO3 with [N(CH3)4]Br and [N(C2H5)4]Br have provided two bromoxenate salts, [N(C2H5)4]3[Br3(XeO3)3] and [N(CH3)4]4[Br4(XeO3)4], in which the cage anions have Xe-Br bond lengths that range from 3.0838(3) to 3.3181(8) Å. The isostructural chloroxenate anions (Xe-Cl bond lengths, 2.9316(2) to 3.101(4) Å) were synthesized by analogy with their bromine analogues. The bromo- and chloroxenate salts are stable in the atmosphere at room temperature and were characterized in the solid state by Raman spectroscopy and low-temperature single-crystal X-ray diffraction, and in the gas phase by quantum-chemical calculations. They are the only known examples of cage anions that contain a noble-gas element. The Xe-Br and Xe-Cl bonds are very weakly covalent and can be viewed as σ-hole interactions, similar to those encountered in halogen bonding. However, the halogen atoms in these cases are valence electron lone pair donors, and the σ*Xe-O orbitals are lone pair acceptors.

Zebrafish embryo toxicity of 15 chlorinated, brominated, and iodinated disinfection by-products

Disinfection to protect human health occurs at drinking water and wastewater facilities through application of non-selective oxidants including chlorine. Oxidants also transform organic material and form disinfection by-products (DBPs), many of which are halogenated and cyto- and genotoxic. Only a handful of assays have been used to compare DBP toxicity, and researchers are unsure which DBP(s) drive the increased cancer risk associated with drinking chlorinated water. The most extensive data set employs an in vitro model cell, Chinese hamster ovary cells. Traditionally, most DBP research focuses on the threat to human health, but the effects on aquatic species exposed to DBPs in wastewater effluents remain ill defined. We present the developmental toxicity for 15 DBPs and a chlorinated wastewater to a model aquatic vertebrate, zebrafish. Mono-halogenated DBPs followed the in vivo toxicity rank order: acetamides>acetic acids>acetonitriles~nitrosamines, which agrees well with previously published mammalian in vitro data. Di- and tri-halogenated acetonitriles were more toxic than their mono-halogenated analogues, and bromine- and iodine-substituted DBPs tended to be more toxic than chlorinated analogues. No zebrafish development effects were observed after exposure to undiluted or non-concentrated, chlorinated wastewater. We find zebrafish development to be a viable in vivo alternative or confirmatory assay to mammalian in vitro cell assays.

Goryainovite, Ca2PO4Cl, a new mineral from the Stora Sahavaara iron ore deposit (Norrbotten, Sweden)

Goryainovite, Ca2PO4Cl, is a new halophosphate, the chlorine analogue of ‘spodiosite’, Ca2PO4F. It is orthorhombic, Pbcm, a = 6.215(2), b = 7.011(2), c = 10.788(3) Å, V = 470.0(8) Å3, Z = 4 (from powder X-ray diffraction data). The mineral is found in a magnetite-serpentine rock of the Stora Sahavaara iron ore deposit (67.408°N 23.297°E) where it forms small (up to 20 μm in diameter) rounded inclusions in magnetite, in close association with hydroxylapatite–chlorapatite, pyrrhotite, pyrite, chalcopyrite, valleriite and thorianite. Goryainovite is a transparent, colourless mineral with a vitreous lustre and a white streak. Cleavage is not observed, and the fracture is conchoidal. The Mohs hardness is c. 4. In transmitted light, the mineral is colourless, biaxial (–), β ≈ 1.66 (for λ = 589 nm). Dcalc = 2.98 g·cm−3. The mean chemical composition specified with electron microprobe is (wt.%): P2O5 33.19, Cl 16.96, CaO 53.25, O = Cl –3.83, total 99.57. The empirical formula calculated on the basis of 3 cations per molecule is Ca2.01[P0.99O3.98]Cl1.01. The simplified formula is Ca2PO4Cl. The strongest X-ray powder diffraction lines [d in Å, (I), (hkl)] are 2.845(90)(113), 2.746(100)(211), 2.333(25)(114), 2.028(15)(132), 1.9569 (30)(115), 1.8370 (20)(025). The Raman spectrum of goryainovite includes 10 bands of -group vibrations. Goryainovite represents probably an early-formed phosphate of the magnetite-serpentine rock and crystallized together with magnetite. When chlorine fugacity decreased, almost all goryainovite was transformed into chlorapatite–hydroxylapatite, and only grains isolated in magnetite remained unaltered. The mineral is named in honour of Prof. Pavel M. Goryainov (b. 1937) for his contribution to the knowledge of the geology and petrology of banded iron formation of the north-eastern part of the Fennoscandian Shield.

Chlorosome-Inspired Synthesis of Templated Metallochlorin-Lipid Nanoassemblies for Biomedical Applications.

Chlorosomes are vesicular light-harvesting organelles found in photosynthetic green sulfur bacteria. These organisms thrive in low photon flux environments due to the most efficient light-to-chemical energy conversion, promoted by a protein-less assembly of chlorin pigments. These assemblies possess collective absorption properties and can be adapted for contrast-enhanced bioimaging applications, where maximized light absorption in the near-infrared optical window is desired. Here, we report a strategy for tuning light absorption toward the near-infrared region by engineering a chlorosome-inspired assembly of synthetic metallochlorins in a biocompatible lipid scaffold. In a series of synthesized chlorin analogues, we discovered that lipid conjugation, central coordination of a zinc metal into the chlorin ring, and a 3(1)-methoxy substitution were critical for the formation of dye assemblies in lipid nanovesicles. The substitutions result in a specific optical shift, characterized by a bathochromically shifted (72 nm) Qy absorption band, along with an increase in absorbance and circular dichroism as the ratio of dye-conjugated lipid was increased. These alterations in optical spectra are indicative of the formation of delocalized excitons states across each molecular assembly. This strategy of tuning absorption by mimicking the structures found in photosynthetic organisms may spur new opportunities in the development of biophotonic contrast agents for medical applications.