Br Anions Research Articles

High-spin Ni(ii) clusters: triangles and planar tetranuclear complexes

The exploration of the NiX(2)/py(2)CO/Et(3)N (X = F, Cl, Br, I; py(2)CO = di-2-pyridyl ketone; Et(3)N = triethylamine) reaction system led to the tetranuclear [Ni(4)Cl(2){py(2)C(OH)O}(2){py(2)C(OMe)O}(2)(MeOH)(2)]Cl(2)·2Et(2)O (1·2Et(2)O) and [Ni(4)Br(2){py(2)C(OH)O}(2){py(2)C(OMe)O}(2)(MeOH)(2)]Br(2)·2Et(2)O (2·2Et(2)O) and the trinuclear [Ni(3){py(2)C(OMe)O}(4)]I(2)·2.5MeOH (3·2.6MeOH), [Ni(3){py(2)C(OMe)O}(4)](NO(3))(0.65)I(1.35)·2MeOH (4·2MeOH) and [Ni(3){py(2)C(OMe)O}(4)](SiF(6))(0.8)F(0.4)·3.5MeOH (5·3.5MeOH) aggregates. The presence of the intermediate size Cl(-) and Br(-) anions resulted in planar tetranuclear complexes with a dense hexagonal packing of cations and donor atoms (tetramolybdate topology) where the X(-) anions participate in the core acting as bridging ligands. The F(-) and I(-) anions do not favour the above arrangement resulting in triangular complexes with an isosceles topology. The magnetic properties of 1-3 have been studied by variable-temperature dc, variable-temperature and variable-field ac magnetic susceptibility techniques and magnetization measurements. All complexes are high-spin with ground states S = 4 for 1 and 2 and S = 3 for 3.

Synthesis, crystal and band structures, and optical properties of a novel quaternary mercury and cadmium chalcogenidehalide: (Hg2Cd2S2Br)Br

A novel quaternary mercury and cadmium chalcogenidehalide, (Hg2Cd2S2Br)Br (1), has been prepared by solid-state reaction and structurally characterized by single crystal X-ray diffraction analysis. The structure of 1 is composed of parallel slabs stacking with -ABAB- mode via linearly coordinated Hg atoms to form a 3D cationic network with the channels being occupied by discrete Br anions, in which the slab consists of interlinks of linear (HgS2Br2) tetrahedral chains and (CdS2Br) trigonal chains. The optical properties were investigated in terms of the diffuse reflectance and Fourier transform infrared spectra. The electronic band structure along with density of states (DOS) calculated by DFT method indicates that the present compound is a semiconductor with an indirect band gap, and that the optical absorption is mainly originated from the charge transitions from Br-4p and S-3p to Cd-5s and Hg-6s states.

Hexaaquamagnesium dibromide 5-(pyridinium-3-yl)tetrazol-1-ide

In the title compound, [Mg(H2O)6]Br2·2C6H5N5, the MgII atom, lying on an inversion center, is coordinated by six water mol­ecules in a distorted octa­hedral geometry. The pyridine and tetra­zole rings in the 5-(pyridinium-3-yl)tetra­zol-1-ide zwitterion are nearly coplanar, twisted from each other by a dihedral angle of 5.70 (1)°. The zwitterions, Br anions and complex cations are connected by O—H⋯Br, O—H⋯N and N—H⋯Br hydrogen bonds, leading to the formation of a three-dimensional network.

Dibromidobis(pyridine-3-carbonitrile-κN1)zinc(II)

In the title compound, [ZnBr2(C6H4N2)2], the ZnII atom is four coordinated in a slightly distorted tetra­hedral fashion by two pyridine N atoms and two Br− anions. π–π inter­actions between adjacent pyridine rings [centroid–centroid distance = 3.6229 (19) Å] are the main factor controlling the packing and are effective in the stabilization of the crystal structure.

4-(1H-Tetrazol-5-yl)pyridinium bromide

In the cation of the title compound, C6H6N5 +·Br−, the pyridine and tetra­zole rings are nearly coplanar, forming a dihedral angle of 6.41 (2)°. The organic cations inter­act with the Br− anions by N—H⋯Br hydrogen bonds, leading to the formation of chains parallel to the b axis.

Trans-Bis(N,N-diethylethylenediamine)nickel(II) dibromide

The structure of the title compound, [Ni(C6H16N2)2]Br2 or [Ni(Et2en)2]Br2 (Et2en is asymmetric N,N-diethyl­ethylene­diamine), containing an NiII atom (site symmetry ) in square-planar NiN4 coordination, is described and contrasted with related structures containing NiII in octa­hedral coordination with axial X − ligands (X − = variable anions). The dialkyl­ated N atom has an appreciably longer bond length to the NiII atom [1.9666 (13) Å] than does the unsubstituted N atom [1.9202 (14) Å]. The Ni—N bond lengths in [Ni(Et2en)2]Br2 are significantly shorter than corresponding values in tetra­gonally distorted [Ni(Et2en)2 X 2] compounds (X = −O2CCF3, OH2, or −NCS), which have a triplet ground state. The electronic configuration in these axially ligated [Ni(Et2en)2 X 2] compounds populates the metal-based d x 2 -y 2 orbital, which is Ni—N anti­bonding in character. Each Et2en ligand in each [Ni(Et2en)2]2+ cation forms a pair of N—H⋯Br hydrogen bonds to the Br− anions, one above and below the NiN4 square plane. Thus, a ribbon of alternating Br− pairs and [Ni(Et2en)2]2+ cations that are canted at 65° relative to one another is formed by hydrogen bonds.

4-Ethoxyanilinium bromide

The title compound, C8H12NO+·Br−, is built up from roughly planar (r.m.s. deviation for the non-H atoms = 0.062 Å) protonated 4-eth­oxy­anilimium cations and Br− anions. In the crystal, the cations and anions are linked by N—H⋯Br and N—H⋯(Br,Br) hydrogen bonds, generating (100) sheets. Very weak C—H⋯π inter­actions may also help to stabilize the crystal structure.

In situ photoelectrocatalytic generation of bactericide for instant inactivation and rapid decomposition of Gram-negative bacteria

A bactericidal technique (PEC–Br) utilizing in situ photoelectrocatalytically generated photoholes (h +), long-lived di-bromide radical anions ( Br 2 - ) and active oxygen species (AOS) for instant inactivation and rapid decomposition of Gram-negative bacteria such as Escherichia coli ( E. coli) was proposed and experimentally validated. The method is capable of inactivating 99.90% and 100% of 9 × 10 6 CFU/mL E. coli within 0.40 s and 1.57 s, respectively. To achieve the same inactivation effect, the proposed method is 358 and 199 times faster than that of the photoelectrocatalytic method in the absence of Br −, and 2250 and 764 times faster than that of the photocatalytic method in the absence of Br −. The decomposition experimental results obtained from 600-s PEC–Br-treated samples demonstrated that over 90% of E. coli body mass was decomposed and 42% biological carbon contents in the sample was completely mineralized and converted into CO 2. The mechanistic pathways of disinfection/decomposition by photocatalysis (PC), photoelectrocatalysis (PEC), and photoelectrocatalysis in presence of Br − (PEC–Br) were also illustrated based on experimental evidence.

Synthesis and Coordination Chemistry of Two N2-Donor Chelating Di(indazolyl)methane Ligands: Structural Characterization and Comparison of Their Metal Chelation Aptitudes

The N(2)-donor bidentate ligands di(1H-indazol-1-yl)methane (L(1)) and di(2H-indazol-2-yl)methane (L(2)) (L in general) have been synthesized, and their coordination behavior toward Zn(II), Cd(II), and Hg(II) salts has been studied. Reaction of L(1) and L(2) with ZnX(2) (X = Cl, Br, or I) yields [ZnX(2)L] species (1-6), that, in the solid state, show a tetrahedral structure with dihapto ligand coordination via the pyrazolyl arms. The reaction of L(1) and L(2) with Zn(NO(3))(2)·6H(2)O is strongly dependent on the reaction conditions and on the ligand employed. Reaction of L(1) with equimolar quantities of Zn(NO(3))(2)·6H(2)O yields the neutral six-coordinate species [Zn(NO(3))(2)(L(1))], 7. On the other hand the use of L(1) excess gives the 2:1 adduct [Zn(NO(3))(2)(L(1))(2)], 8 where both nitrates act as a unidentate coordinating ligand. Analogous stoichiometry is found in the compound obtained from the reaction of L(2) with Zn(NO(3))(2)·6H(2)O which gives the ionic [Zn(NO(3))(L(2))(2)](NO(3)), 10. Complete displacement of both nitrates from the zinc coordination sphere is observed when the reaction between L(1) excess and the zinc salt was carried out in hydrothermal conditions. The metal ion type is also determining structure and stoichiometry: the reaction of L(2) with CdCl(2) gave the 2:1 adduct [CdCl(2)(L(2))(2)] 11 where both chlorides complete the coordination sphere of the six-coordinate cadmium center; on the other hand from the reaction of L(1) with CdBr(2) the polynuclear [CdBr(2)(L(1))](n) 12 is obtained, the Br(-) anion acting as bridging ligands in a six-coordinate cadmium coordination environment. The reaction of L(1) and L(2) with HgX(2) (X = Cl, I, SCN) is also dependent on the reaction conditions and the nature of X, two different types of adducts being formed [HgX(L)] (14: L = L(1), 16, 17: L = L(1) or L(2), X = I, 19: L = L(2), X = SCN) and [HgX(L)(2)] (15: L = L(2), X = Cl, 18: L = L(1), X = SCN). The X-ray diffraction analyses of compounds 1, 2, 4, 5, 7, 8, 10-12, 14, 15, and 19 are also reported. The variations of the coordination geometry parameters in the complexes are compared and discussed.

Theoretical elucidation on the functional role of pyrrolidine‐type ionic liquids in inducing stereoselectivity of the Michael addition of cyclohexanone with trans‐β‐nitrostyrene

Density functional theory calculations have been carried out to elucidate the stereoselectivity of the Michael addition of cyclohexanone with trans-β-nitrostyrene, induced by a chiral ionic liquid (CIL) pyrrolidine-imidazolium bromide. By comparison of the C-C bond forming processes in the absence and presence of Br(-) anion, we found that intermolecular H-bonds between the imidazolium cation and the nitro group of trans-β-nitrostyrene and the steric hindrance of the imidazolium cation moiety on the Si-face of enamine dominate the stereoselectivity of the Michael addition. The presence of Br(-) anion obviously reduces the barrier by increasing the polarity of the C4=C5 bond of enamine. The theoretical results rationalize well the early experimental finding, and reveal a valuable clue for the further CIL design with high catalytic efficiency.

Poly[[μ2-1,2-bis(4-pyridyl)ethene-κ2N:N′]-di-μ3-bromido-dicopper(I)

In the title polymeric CuI compound, [Cu2Br2(C12H10N2)]n, the Cu cation is coordinated by an N atom from the 1,2-bis­(4-pyrid­yl)ethene ligand and three Br− anions in a distorted tetra­hedral CuBr3N coordination geometry. Each Br− anion bridges three Cu cations related by inversion centers, forming a stair-like polymeric chain along the a axis, and the terminal N atoms of the 1,2-bis­(4-pyrid­yl)ethene ligand, located across an inversion center, coordinate the Cu cations from neighboring chains, forming polymeric sheets.

Dipole-bound states of the alkali–superhalogen anions: [formula omitted] (X = F, Cl, Br)

The dipole-bound states of the LiBeX 3 - (X = F, Cl, Br) anions were predicted at the MP2/aug-cc-pVDZ+5 s5 p level of theory. Upon electron attachment, the neutral LiBeX 3 host shows noteworthy geometrical relaxation, which is accompanied by a significant increase of the dipole moment. The LiBeX 3 - anions exhibit large vertical electron detachment energies of 539.2–886.5 MeV at the CCSD(T)/aug-cc-pVDZ+6 s6 p4 d level, indicating that the binding of electrons to the alkali–superhalogen LiBeX 3 molecules is feasible. In addition, the stabilities of the LiBeX 3 - anions with respect to the neutral hosts, are found to be closely related to the electronegativity of the X ligands and partial atomic charge localized on Be.

Novel 1D Cu(I) coordination polymers formed by the combination of Cu(I) halides and 4-(2-pyridyl)pyrimidine

Three novel 1D Cu(I) coordination polymers [Cu 4X 4(pprd) 2] n (X = Cl( 1), Br( 2) and I( 3); pprd = 4-(2-pyridyl)pyrimidine) were systematically synthesized by Cu(I) halides and the pprd ligand, and they have been characterized by X-ray, IR, and TG-DTA analyses. The molecular structure of complex 1 essentially resembles to that of complex 2. In complexes 1 and 2, four Cu(I) atoms are bridged by four Cl or Br anions to form an eight-membered Cu 4X 4 framework in the twist-chair form. Furthermore, the Cu 4X 4 frameworks are coordinated by the chelate and bridging sites of two pprd ligands to form a unique 1D two-stepped Cu(I) coordination polymer, in which two stairs are formed by the Cu 4X 4 core and two heteroaromatic planes of pprd. In the crystal packing structures, it is interesting that two heteroaromatic planes of pprd are stacking along the b-axis for complex 1 and the a-axis for complex 2. In contrast, four Cu(I) atoms in complex 3 are bridged by four I atoms to form a Cu 4I 4 stepped cubane tetramer. Additionally, the Cu 4I 4 stepped cubane cores are linked by the chelate and bridging sites of two pprd ligands to form an infinite 1D zigzag-chain Cu(I) coordination polymer. The thermal decomposition behaviors for Cu(I)–X/pprd complexes 1, 2 and 3 were determined by thermogravimetric analysis (TG-DTA). Although the thermal decomposition behaviors of complex 1 were unidentified, those of complexes 2 and 3 were assigned. The mass loss at the first stage of thermal decomposition for polymeric [Cu 4X 4(pprd) 2] n was identical to the formation of oligomeric [Cu 4X 4(pprd)] by the elimination of one pprd molecule. The mass loss at the next stage was decided to the formation of Cu 4X 4 by the elimination of another pprd molecule.

Polymers based on ionic monomers with side phosphonate groups

A number of new ionic vinyl monomers composed of 1�vinylimidazolium cation with diethoxy� and dihydroxyphosphoryl groups and various anions—Br - , (CN)2N - , and (CF3SO2)2N - —are synthesized. The freeradical polymerization of the monomers in solutions of molecular and ionic solvents yields new polymer analogs of ionic liquids, and their molecularmass characteristics, solubility, heat resistance, thermal stability, and electrical conductivity are estimated. It is shown that the incorporation of bulky phosphorylalkyl side substituents into the vinylimidazolium polycation causes a decrease in the glasstransition temperature and an increase in the ionic conductivity of polymer salts. The highest ionic conductivity (2.6 × 10 -5 S/cm at 25°C) is exhibited by the polymer with the (CN)2N - anion.

Meso-[5,5,7,12,12,14-Hexamethyl-1,4,8,11-tetraazacyclotetradeca-1(14),7-diene]nickel(II) dibromide dihydrate

The asymmetric unit of the title complex, [Ni(C16H32N4)]Br2·2H2O, contains two [Ni(C16H32N4)]2+ cations, four Br− anions and four uncoordinated H2O mol­ecules. The Ni atoms are in a slightly distorted square-planar coordination by the four macrocyclic N atoms, which are almost coplanar [N—N—N—N torsion angles of 2.97 (6) and 3.12 (7)°]. In the crystal, a network of N—H⋯Br, O—H⋯Br and N—H⋯O hydrogen bonds leads to the formation of a chain structure.

Continuous Symmetry Breaking Induced by Ion Pairing Effect in Heptamethine Cyanine Dyes: Beyond the Cyanine Limit

The association of heptamethine cyanine cation 1(+) with various counterions A (A = Br(-), I(-), PF(6)(-), SbF(6)(-), B(C(6)F(5))(4)(-), TRISPHAT) was realized. The six different ion pairs have been characterized by X-ray diffraction, and their absorption properties were studied in polar (DCM) and apolar (toluene) solvents. A small, hard anion (Br(-)) is able to strongly polarize the polymethine chain, resulting in the stabilization of an asymmetric dipolar-like structure in the crystal and in nondissociating solvents. On the contrary, in more polar solvents or when it is associated with a bulky soft anion (TRISPHAT or B(C(6)F(5))(4)(-)), the same cyanine dye adopts preferentially the ideal polymethine state. The solid-state and solution absorption properties of heptamethine dyes are therefore strongly correlated to the nature of the counterion.

Capacitively coupled contactless conductivity detection with dual top–bottom cell configuration for microchip electrophoresis

An optimized capacitively coupled contactless conductivity detector for microchip electophoresis is presented. The detector consists of a pair of top-bottom excitation electrodes and a pair of pickup electrodes disposed onto a very thin plastic microfluidic chip. The detection cell formed by the electrodes is completely encased and shielded in a metal housing. These approaches allow for the enhancement of signal coupling and extraction from the detection cell that result in an improved signal-to-noise-ratio and detection sensitivity. The improved detector performance is illustrated by the electrophoretic separation of six cations (NH(4) (+), K(+), Ca(2+), Na(+), Mg(2+), Li(+)) with a detection limit of approximately 0.3 microM and the analysis of the anions (Br(-), Cl(-), NO(2) (-), NO(3) (-), SO(4) (2-), F(-)) with a detection limit of about 0.15 microM. These LODs are significantly improved compared with previous reports using the conventional top-top electrode geometry. The developed system was applied to the analysis of ions in bottled drinking water samples.

In situ Formation of NOx and Br Anion for Aerobic Oxidation of Benzylic Alcohols without Transition Metal

The reaction of KBrO 3 and NH 2 OH·HCl in situ generates NO x and Br amon, which combine with 2,2,6,6-tetrametnylpiperidine-N-oxide (TEMPO) to construct a NO-activating dioxygen, Br-assisted, TEMPO-catalyzed aerobic oxidation of alcohols. Catalyzed by KBrO/NH 2 OH·HCl/TEMPO, various benzylic alcohols can be oxidized quantitatively to their corresponding carbonyl compounds under mild conditions. The easy handling and simple product separation make the process an attractive candidate for the oxidation of alcohols.

Cinchona-Derived Quaternary Ammonium Salts-Improved Asymmetric Cycloaddition of CO2 to Epoxides

Abstract A new catalyst system, SalenCoX/cinchona-derived quaternary ammonium salts, was developed to catalyze the cycloaddition of CO 2 to epoxides under extremely mild reaction conditions. Chiral propylene carbonate was obtained with good enantioselectivity in the presence of the catalyst. The anions of the catalyst and the cocatalyst evidently affect the activity and enantioselectivity of the reaction. The activity of ( S,S )-catalysts in terms of anion is in the order 2-nitrophenoxy > 2,4,6-trinitrophenoxy > NO 3 − > OAc − > CF 3 CO 2 − ≈ Br − > Cl − > OTs − . The cocatalyst with anion Cl − gives the highest ee value for propylene carbonate. In contrast, the cocatalyst with anion Br − has higher activity. When the catalyst ( S,S )-(+)-1,2-cyclohexanediamino( N,N -bis(3,5-di- tert -butyl-salicylidene) cobalt(III) acetate (( S,S )- A ) was combined with the cocatalyst N,O -dibenzylquininium chloride ( 1a ), it gives the highest 73% ee for propylene carbonate.

Trans-Dibromidobis[tris(4-chlorophenyl)phosphine]palladium(II)

In the title compound, [PdBr2(C18H12Cl3P)2], the PdII ion is situated on a centre of symmetry and is coordinated by two Br anions [Pd—Br = 2.4252 (2) Å] and two P-donor ligands [Pd—P = 2.3317 (6) Å] in a slightly distorted square-planar geometry [P—Pd—Br = 86.589 (15)°].