Bromide Coordination Research Articles

Manganese(II) Bromide Coordination toward the Target Product and By-Product of the Condensation Reaction between 2-Picolylamine and Acenaphthenequinone

A heteroleptic binuclear manganese complex was obtained and characterized by single-crystal X-ray diffraction. Manganese ions coordinate with the target product and by-product of the condensation reaction between 2-picolylamine and acenaphthenequinone are characterized by different geometries in the resulting complex.

Solvent-Induced Cobalt(II) Cyanoguanidine Bromides: Syntheses, Crystal Structure, Optical and Magnetic Properties

Two different phase-pure cobalt(II) cyanoguanidine bromide coordination compounds, Co(C2N4H4)2(H2O)4·2Br·2H2O (1) and Co3(C2N4H4)8(H2O)8·6Br (2), were precipitated from aqueous and methanol solutions, respectively, and their structures were solved and refined from X-ray single-crystal data at 100 K. Both 1 and 2 crystallize in the triclinic system with space group P1¯. The structure of 1 consists of two crystallographically distinct isolated CoO4N2 octahedral units plus bromide anions and crystal water molecules, whereas 2 is built from both isolated octahedra and discrete binuclear cluster units made from edge-sharing octahedra. Diffuse reflectance spectra and IR analysis then go on to highlight optical and vibrational differences between these two compounds. The magnetic susceptibility of 1 is consistent with either isolated or very weakly interacting Co2+ centers whereas the magnetic susceptibility of 2 evidences the potential weak antiferromagnetic exchange interactions that may arise from superexchange within the binuclear clusters.

In-situ debromination mechanism based on self-activation and catalysis of Ca(OH)2 during pyrolysis of waste printed circuit boards

Completely and deeply removed bromide from waste printed circuit boards (WPCBs) is necessary due to their toxicity and carcinogenicity. To achieve this purpose, calcium hydroxide (Ca(OH)2) as a debromination agent was added during pyrolysis process of WPCBs. The results showed that hydrogen bromide (HBr), 4-bromophenol, 2-bromophenol and 2,4-dibromophenol were the main bromide species in pyrolysis products. The Ca(OH)2 plays a significant role for removing HBr and organic bromide, but not affects products yield. Optimal removal efficiency for 4-bromophenol, 2-bromophenol and 2,4-dibromophenol reached 87.5 %, 74.6 % and 54.5 %, respectively. And debromination efficiency was related to the steric hindrance caused by bromide atoms. The Ca(OH)2 can be activated by captured HBr and its thermal decomposition. And the newly-generated calcium bromide and calcium oxide significantly facilitate debromination due to their high surface energy and reactivity. The debromination mechanism was clarified by experiments coupled with computational chemistry: the coordination of bromide and calcium to form [Ph-Br···Ca2+] or [Ph-Br···Caatom]. Then, electrons were delivered form bromide atom to Ca2+ or Caatom, which resulted in the stretch and weaken the C-Br bond. Hence, the C-Br bond was more easily to break. This work can provide support for designing novel and efficient debromination agents applied for high-temperature system.

Crystal structures of four dimeric manganese(II) bromide coordination complexes with various derivatives of pyridine N-oxide.

Four manganese(II) bromide coordination complexes have been prepared with four pyridine N-oxides, viz. pyridine N-oxide (PNO), 2-methyl-pyridine N-oxide (2MePNO), 3-methyl-pyridine N-oxide (3MePNO), and 4-methyl-pyridine N-oxide (4MePNO). The compounds are bis-(μ-pyridine N-oxide)bis-[aqua-dibromido-(pyridine N-oxide)manganese(II)], [Mn2Br4(C5H5NO)4(H2O)2] (I), bis-(μ-2-methyl-pyridine N-oxide)bis-[di-aqua-dibromido-manganese(II)]-2-methyl-pyridine N-oxide (1/2), [Mn2Br4(C6H7NO)2(H2O)4]·2C6H7NO (II), bis-(μ-3-methyl-pyridine N-oxide)bis-[aqua-dibromido-(3-methyl-pyridine N-oxide)manganese(II)], [Mn2Br4(C6H7NO)4(H2O)2] (III), and bis-(μ-4-methyl-pyridine N-oxide)bis-[di-bromido-methanol(4-methyl-pyridine N-oxide)manganese(II)], [Mn2Br4(C6H7NO)4(CH3OH)2] (IV). All the compounds have one unique MnII atom and form a dimeric complex that contains two MnII atoms related by a crystallographic inversion center. Pseudo-octa-hedral six-coordinate manganese(II) centers are found in all four compounds. All four compounds form dimers of Mn atoms bridged by the oxygen atom of the PNO ligand. Compounds I, II and III exhibit a bound water of solvation, whereas compound IV contains a bound methanol mol-ecule of solvation. Compounds I, III and IV exhibit the same arrangement of mol-ecules around each manganese atom, ligated by two bromide ions, oxygen atoms of two PNO ligands and one solvent mol-ecule, whereas in compound II each manganese atom is ligated by two bromide ions, one O atom of a PNO ligand and two water mol-ecules with a second PNO mol-ecule inter-acting with the complex via hydrogen bonding through the bound water mol-ecules. All of the compounds form extended hydrogen-bonding networks, and compounds I, II, and IV exhibit offset π-stacking between PNO ligands of neighboring dimers.

Macrocyclic Receptor for Precious Gold, Platinum, or Palladium Coordination Complexes.

Two macrocyclic tetralactam receptors are shown to selectively encapsulate anionic, square-planar chloride and bromide coordination complexes of gold(III), platinum(II), and palladium(II). Both receptors have a preorganized structure that is complementary to its precious metal guest. The receptors do not directly ligate the guest metal center but instead provide an array of arene π-electron donors that interact with the electropositive metal and hydrogen-bond donors that interact with the outer electronegative ligands. This unique mode of supramolecular recognition is illustrated by six X-ray crystal structures showing receptor encapsulation of AuCl4-, AuBr4-, PtCl4-2, or Pd2Cl6-2. In organic solution, the 1:1 association constants correlate with specific supramolecular features identified in the solid state. Technical applications using these receptors are envisioned in a wide range of fields that involve precious metals, including mining, recycling, catalysis, nanoscience, and medicine.

Influence of water on the structure and magnetic properties of a copper bromide coordination compound with 3-amino-4-ethoxycarbonylpyrazole

The influence of water on a polynuclear [CuL2Br2]n (1) copper bromide compound with 3-amino-4-ethoxycarbonylpyrazole (L) is investigated.

Aurophilicity in Action: Fine-Tuning the Gold(I)-Gold(I) Distance in the Excited State To Modulate the Emission in a Series of Dinuclear Homoleptic Gold(I)-NHC Complexes.

The solution-state emission profiles of a series of dinuclear Au(I) complexes 4-6 of the general formula Au2(NHC-(CH2)n-NHC)2Br2, where NHC = N-benzylbenzimidazol-2-ylidene and n = 1-3, were found to be markedly different from each other and dependent on the presence of excess bromide. The addition of excess bromide to the solutions of 4 and 6 leads to red shifts of ca. 60 nm, and in the case of 5, which is nonemissive when neat, green luminescence emerges. A detailed computational study undertaken to rationalize the observed behavior revealed the determining role aurophilicity plays in the photophysics of these compounds, and the formation of exciplexes between the complex cations and solvent molecules or counterions was demonstrated to significantly decrease the Au-Au distance in the triplet excited state. A direct dependence of the emission wavelength on the strength of the intracationic aurophilic contact allows for a controlled manipulation of the emission energy by varying the linker length of a diNHC ligand and by judicial choice of counterions or solvent. Such unique stimuli-responsive solution-state behavior is of interest to prospective applications in medical diagnostics, bioimaging, and sensing. In the solid, the investigated complexes are intensely phosphorescent and, notably, 5 and 6 exhibit reversible luminescent mechanochromism arising from amorphization accompanied by the loss of co-crystallized methanol molecules. The mechano-responsive properties are also likely to be related to changes in bromide coordination and the ensuing alterations of intramolecular aurophilic interactions. Somewhat surprisingly, the photophysics of NHC ligand precursors 2 and 3 is related to the formation of ground-state associates with bromide counterions through hydrogen bonding, whereas 1 does not appear to bind its counterions.

Homosynthon Robustness in the Stabilization of New 1D Polymeric Mercury(II) Complex With Anthranilic Acid Ligand and Generation of 3D Supramolecular Network: Experimental and DFT Studies

A new mercury(II) bromide coordination polymer of anthranilic acid (Ant), {[Hg2(μ2-Br)3(μ3-Br)(Ant)].[Ant]}n, was synthesized and characterized. The structure determination revealed that coordinated and noncoordinated forms of anthranilic acid create strong hydrogen bonding via carboxylate groups as a supramolecular R22(8) homosynthon. Because of the existence of a rare coordination mode of ligand, theoretical calculations on the stability of the fragment models of [Hg6Br12(Ant)2](Ant)2 (with synthon) and Hg6Br12(Ant)2 (without synthon) have been performed using density functional theory. The results showed that the robust homosynthon has the important role on the stabilization of structure with the scarce binding mode of ligand.

Synthesis, Structure, and Properties of a Copper Bromide Coordination Compound with 3-Amino-4-EthoxyCarbonylPyrazole. Nature of the Nonresonant and Ferromagnetic Absorption Observed by EPR

Synthesis, structure, and magnetic properties of copper bromide CuL2Br2 with 3-amino-4-ethoxycarbonylpyrazole (L) are presented. The CuL2Br2 is a 1D polymer complex and crystal structure has triclinic symmetry with space group P-1. The examined compound has thermochromic properties (russet ↔ light red), and its magnetic properties are changed from paramagnetic to nonresonance and ferromagnetic ones after heat treatment (300 → 77 → 300 K) or pressure treatment (1 → 3,000 → 1 atm).

Anion...π interactions in copper(I) chloride and bromide coordination polymers bearing 1,4-bis(pyridazin-4-yl)benzene ligands

In poly[[μ4-1,4-bis(pyridazin-4-yl)benzene-1:2:3:4κ(4)N(1):N(2):N(1'):N(2')]di-μ2-chlorido-dicopper(I)], [Cu2Cl2(C14H10N4)]n, (I), and its isomorphous bromide analogue, [Cu2Br2(C14H10N4)]n, (II), the organic ligand is situated across a centre of inversion. The Cu(I) cations adopt a distorted tetrahedral [CuN2X2] [X = Cl in (I) or Br in (II)] environment [Cu-N = 2.0183 (14)-2.0936 (14) Å; Cu-Cl = 2.2686 (6) and 2.4241 (5) Å; Cu-Br = 2.4002 (6) and 2.5284 (5) Å] and the primary coordination motif consists of cuprohalogenide chains accommodating μ-pyridazine groups. The organic ligands are tetradentate and link the inorganic chains into corrugated layers. Their packing is influenced by interlayer anion···π interactions [Cl···π = 3.540 (2) Å and Br···π = 3.593 (2) Å] with the electron-deficient pyridazine rings. This kind of interaction precludes the characteristic slipped π-π stacking and close parallel alignment of the organic tectons; it may be involved as a structure-defining factor for coordination layers based upon lengthy polyaromatic linkers.

Solid state structural transformation of bromide coordination polymer to chloride by anion replacement; new precursors for preparation of PbBr2 and PbCl2 nanoparticles

Reversible anion-exchange of 2D lead(ii) coordination polymers from [Pb(4-bpdb)Br2]n (1) to [Pb(4-bpdb)Cl2]n (2) by solid state anion-replacement has been studied.

Solid state and sonochemical syntheses of nano lead(II) chloride and bromide coordination polymers from its nitrate analog via mechanochemical crystal to crystal transformations

Reversible crystal-to-crystal transformations of 3D lead(II) coordination polymers with the ligand 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene (4-bpdh), from nitrate analoge [Pb(4-bpdh)(NO3)2(H2O)]n (1) to [Pb(4-bpdh)(NO3)(Br)]n (2), [Pb(4-bpdh)(Br)2]n (3), [Pb(4-bpdh)(NO3)(Cl)]n (4) and [Pb(4-bpdh)(Cl)2]n (5) by solid state anion-replacement processes under mechanochemical reactions, have been studied. The reversible solid state structural transformations of compounds 1–5, by anion-replacement processes under mechanochemical reaction, have been verified by PXRD measurements. Nanoparticles of compounds were synthesized by sonochemical process and characterized by scanning electron microscopy (SEM), powder X-ray diffraction, IR spectroscopy and elemental analyses. The SEM images showed that morphology change occurs during solid state anion-replacements of nanocrystals.

The 1:1 co-crystal of triphenyl(2,3,5,6-tetrafluorobenzyl)phosphonium bromide and 1,1,2,2-tetrafluoro-1,2-diiodoethane

The title compound, C25H18F4P+·Br−·C2F4I2, is a 1:1 co-crystal of triphen­yl(2,3,5,6-tetra­fluoro­benz­yl)phospho­nium (TTPB) bromide and 1,1,2,2-tetra­fluoro-1,2-di­iodo­ethane (TFDIE). The crystal structure consists of a framework of TTPB cations held together by C—H⋯Br inter­actions. In this framework, infinite channels along [100] are filled by TFDIE mol­ecules held together in infinite ribbons by short F⋯F [2.863 (2)–2.901 (2)Å] inter­actions. The structure contains halogen bonds (XB) and hydrogen bonds (HB) in the bromide coordination sphere. TFDIE functions as a monodentate XB donor as only one I atom is linked to the Br− anion and forms a short and directional inter­action [I⋯Br− 3.1798 (7) Å and C—I⋯Br− 177.76 (5)°]. The coordination sphere of the bromide anion is completed by two short HBs of about 2.8 Å (for H⋯Br) with the acidic methyl­ene H atoms and two longer HBs of about 3.0 Å with H atoms of the phenyl rings. Surprisingly neither the second iodine atom of TFDIE nor the H atom on the tetra­fluoro­phenyl group make any short contacts.

Energy Shift of the 4f 136s 1 Excited States of Yb2+ from Gas Phase to the CsCaBr3 Solid

ABSTRACT Ab initio calculations on Yb2+-doped CsCaBr3 show a large increase (20000 cm−1) of the 4f 14 → 4f 136s 1 transitions from gas phase to CsCaBr3, due to large embedding effects originated beyond the first bromide coordination shell. The 4f 136s 1 states of (YbBr6)4- in vacuo undergo a sudden energy and electron density change at short Br-Yb distances resulting in the formation of an Yb-trapped exciton, which evolves to full ionization, making Yb(II) unstable in hexabromide coordination in gas phase. Embedding in CsCaBr3 localizes the 6s electron inside the Br6 cage, which increases the 6s-Br6 repulsion and increases the energy of the 4f 136s 1 states.

Syntheses and characterization of a new nano-structured bismuth(III) bromide coordination polymer; new precursor for preparation of bismuth(III) bromide and bismuth(III) oxide nanostructures

Nanoparticles of a Bi(III) coordination polymer, {[Bi(μ-4,4′-bipy)Br4] · (4,4′-Hbipy)} n (1) (4,4′-bipy = 4,4′-bipyridine), were synthesized by a sonochemical method. The new nanoparticles were characterized by scanning electron microscopy, X-ray powder diffraction (XRD), IR spectroscopy, and elemental analyses. Compound 1 was structurally characterized by single-crystal X-ray diffraction. The thermal stabilities of 1 as bulk and at nanosize were studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The Bi2O3 and BiBr3 nanostructures were obtained by calcinations of nanostructure of 1 in air and argon.

2D Holodirected lead(II) bromide coordination polymers constructed of rigid and flexible ligands

Three new 2D Pb II coordination polymers containing 4,4′-bipyridine (4,4′-bipy), 1,2-bis(4-pyridyl)ethane (bpa) and 1,2-bis(4-pyridyl)ethene (bpe) with bromide anions, [Pb(μ-4,4′-bipy)(μ-Br) 2] n ( 1), [Pb(μ-bpa)(μ-Br) 2] n ( 2) and [Pb(μ-bpe)(μ-Br) 2] n ( 3) have been synthesized and characterized by elemental analysis, IR spectroscopy and their structures studied by X-ray crystallography. The thermal stability of compounds 1– 3 was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The single-crystal X-ray data shows that the Pb 2+-ions have coordination numbers of six and contain the rarely holodirected geometries.

The Structure of the Homogeneous Oxidation Catalyst, Mn(II)(Br-1)x, in Supercritical Water: An X-ray Absorption Fine-Structure Study

Extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) spectroscopies were used to probe the first-shell coordination structure about Mn(II) and Br(-1) ions that exist as contact ion pairs in supercritical water. This work was performed to clarify why solutions of MnBr2 in supercritical water are known to effectively catalyze the aerobic oxidative synthesis of terephthalic acid from p-xylene as well as a number of other methylaromatic compounds. The Mn and Br K-edge spectra were collected at the bending magnet beamline (sector 20) at the Advanced Photon Source, Argonne National Laboratory. The first-shell coordination structure about the Mn(II) ion changes from octahedral at ambient conditions to tetrahedral at supercritical conditions. Under supercritical conditions, the measured bond distances of Mn-OH2 and Mn-Br are 2.14 and 2.46 A, respectively. Direct contact ion pairs form with about 2 Br(-1) ions present in the first coordination shell of the Mn(II) ion. The structure of dissolved MnBr2, below 1.0 m, changes from essentially [Mn(II)(H2O)6]+2 to [Mn(II)(H2O)2(Br(-1))2] in supercritical water (scH2O). When an excess of Br(-1) ion is added, the bromide coordination number increases and the number of water molecules decreases. The results show that the initial MnBr2 catalyst in scH2O is tetrahedral with two Mn-Br contact ion pairs. The presence of the acetate anion deactivates the catalyst by formation of insoluble MnO.