Bromide Complexes Research Articles

Synthesis and coordination chemistry of silver(I), gold(I) and gold(III) complexes with picoline-functionalized benzimidazolin-2-ylidene ligands

Abstract The reactions of N-alkyl-N′-picolyl-benzimidazolium bromides or N,N′-dipicolyl-benzimidazolium bromide with silver oxide yielded the silver dicarbene complexes of the type [Ag(NHC)2][AgBr2] 1–4 (NHC = picoline-functionalized benzimidazolin-2-ylidene). The silver complexes 1–4 have been used in carbene transfer reactions to yield the gold(I) complexes of the type [AuCl(NHC)] 5–8 in good yields. A halide exchange at the metal center of complexes 5–8 with lithium bromide yielded the gold bromide complexes 9–12. Finally, the oxidation of the gold(I) centers in complexes 9–12 with elemental bromine gave the gold(III) complexes of the type [AuBr3(NHC)] 13–16. Molecular structures of selected Au(I) and Au(III) complexes have been determined by X-ray diffraction studies.

Deciphering the Mechanistic Details of Manganese-Catalyzed Formic Acid Dehydrogenation: Insights from DFT Calculations.

A comprehensive density functional theory investigation has been carried out to unravel the complete mechanistic landscape of aqueous-phase formic acid dehydrogenation (FAD) catalyzed by a pyridyl-imidazoline-based Mn(I) catalyst [Mn(PY-NHIM)(CO)3Br], which was recently reported by Beller and co-workers. The computed free energy profiles show that for the production of a Mn-formate intermediate [Mn(HCO2-)], a stepwise mechanism is both kinetically and thermodynamically favorable compared to the concerted mechanism. This stepwise mechanism involves the dissociation of a Br- ion from a Mn-bromide complex [Mn(Br)] to create a vacant site and coordination of water solvent to this vacant site, followed by the dissociative exchange of the aqua ligand with the formate ion to form Mn(HCO2-). Non-covalent interaction analysis revealed that the steric hindrance at the transition state is the cardinal reason for the preference to a stepwise mechanism. The β-hydride elimination process was estimated to be the rate-determining step with a barrier of 19.0 kcal/mol. This confirms the experimental observation. The generation of a dihydrogen-bound complex was found to occur through the protonation of Mn-hydride by a hydronium ion instead of formic acid. The mechanistic details and insights presented in this work would promote future catalytic designing and exploration of earth-abundant Mn-based catalytic systems for potential applications toward FAD.

The Mechanism of Adsorption of Rh(III) Bromide Complex Ions on Activated Carbon.

In the paper, the mechanism of the process of the Rh(III) ions adsorption on activated carbon ORGANOSORB 10—AA was investigated. It was shown, that the process is reversible, i.e., stripping of Rh(III) ions from activated carbon to the solution is also possible. This opens the possibility of industrial recovery of Rh (III) ions from highly dilute aqueous solutions. The activation energies for the forward and backward reaction were determined These are equal to c.a. 7 and 0 kJ/mol. respectively. Unfortunately, the efficiency of this process was low. Obtained maximum load of Rh(III) was equal to 1.13 mg per 1 g of activated carbon.

Bi- and Tetranuclear Antimony(III) Bromide Complexes with Alkanediyl-bis(3-methylpyridinium) Cations

Bi- and Tetranuclear Antimony(III) Bromide Complexes with Alkanediyl-bis(3-methylpyridinium) Cations

A new square pyramidal copper(II) complex [Cu(C10H24N4)Br]Br: Crystal structure, thermal analysis, Hirschfeld surfaces, electrical and semiconducting properties

A new organic-inorganic Cu(II) bromide complex material [Cu(C10H24N4)Br]Br has been synthesized by hydrothermal method. Blue-violet crystals are characterized by X‐ray single crystal diffraction, crystallizing in the orthorhombic system, non-centrosymmetric space group P212121, with the following unit-cell parameters: a = 8.3536 (1) Å, b = 12.7161 (3) Å, c = 14.1982 (3) Å, V = 1508.21 (5) Å3. This study shows that the Cu(II) sites adopt a square pyramidal distorted geometry. The crystal structure first reveals a one-dimensional (1D) network along the a axis based on N–H···Br interactions. The dimensionality is further increased to (3D) by C–H···Br weak interactions. Hirshfeld surfaces analysis was used to study the intermolecular interactions in the crystal lattices. It was then found that X-H···Br (X = N or C) contacts play an important role within the atomic architecture. Besides, the phase transitions, electric and optical properties of [Cu(C10H24N4)Br]Br were investigated and revealed a phase transition at T = 343 K. The temperature dependence of the electrical conductivity confirmed the phase transition that was also well detected with differential scanning calorimetry. The calculated activation energies of the conduction process for the two phases are EaI=0.30 eV, and EaII=0.69 eV.

Modelling the Effect of Temperature on the Stability of Bromide and Carbonate Complexes of Europium, Gadolinium, Terbium and Determination of their Thermodynamic Functions

A method has been developed for calculating the stability constants of inorganic complexes of rare-earth metals at various temperatures, based on analysis of the literature data by obtaining a linear regression equation on the form: . Using this method, the stability constants of bromide LnBr2+ and carbonate LnCO3+ complexes of europium, terbium, and gadolinium in aqueous solutions at temperatures of 50, 75, and 100 ° C were obtained. The obtained values of the coefficients А(T1) and В(T1) of the linear regression equation can be used to calculate the stability constants of complexes of europium, terbium, and gadolinium with other inorganic ligands at given temperatures. Based on the temperature dependence of the stability constants of bromide and carbonate complexes, their standard entropies and enthalpies of formation were calculated. Based on the obtained values of the thermodynamic functions, an assumption was made about the outer-sphere or inner-sphere nature of the complex.

Transformation of Formazanate at Nickel(II) Centers to Give a Singly Reduced Nickel Complex with Azoiminate Radical Ligands and Its Reactivity toward Dioxygen.

The heteroleptic (formazanato)nickel bromide complex LNi(μ-Br)2NiL [LH = Mes-NH-N═C(p-tol)-N═N-Mes] has been prepared by deprotonation of LH with NaH followed by reaction with NiBr2(dme). Treatment of this complex with KC8 led to transformation of the formazanate into azoiminate ligands via N-N bond cleavage and the simultaneous release of aniline. At the same time, the potentially resulting intermediate complex L'2Ni [L' = HN═C(p-tol)-N═N-Mes] was reduced by one additional electron, which is delocalized across the π system and the metal center. The resulting reduced complex [L'2Ni]K(18-c-6) has a S = 1/2 ground state and a square-planar structure. It reacts with dioxygen via one-electron oxidation to give the complex L'2Ni, and the formation of superoxide was detected spectroscopically. If oxidizable substrates are present during this process, these are oxygenated/oxidized. Triphenylphosphine is converted to phosphine oxide, and hydrogen atoms are abstracted from TEMPO-H and phenols. In the case of cyclohexene, autoxidations are triggered, leading to the typical radical-chain-derived products of cyclohexene.

Increasing the Activity of Copper Guanidine Quinoline Catalysts: Substitution at the Quinoline Backbone Leads to Highly Active Complexes for ATRP

AbstractCopper bromide complexes with the ligands TMG6NO2qu, TMG6Brqu, TMG6Methoxyqu, TMG6NMe2qu, TMG6EHOqu and TMG6dBAqu were examined regarding their activity in atom transfer radical polymerization (ATRP). The ligands were inspired by 1,1,3,3‐tetramethyl‐2‐(quinolin‐8‐yl)guanidine (TMGqu) and the substituents have been chosen with a large range between electron withdrawing and donating abilities. The donor properties of the ligands can be strongly influenced and further highly active catalysts based on these systems can be obtained. The ligands with strong donating moieties were in addition modified by alkyl groups to increase the solubility in apolar monomers like styrene. CuI and CuII bromide complexes were crystallised and the structural data correlated to the different substituents and the catalyst activity. The electrochemical potentials E1/2, the equilibrium constants KATRP and rate constants kact and kdeact were determined. Polymerizations of styrene were conducted in solution whereas the catalyst based on TMG6EHOqu shows a good solubility and performance in bulk.

The Crystal Structure of a Benzyltriethylammonium Bromide Complex with <i>rac</i>-1,1′-Binaphthalene-2,2′-diol: The Inclusion of an Arylammonium Salt by an Assembly of Binaphthol Groups

The Crystal Structure of a Benzyltriethylammonium Bromide Complex with <i>rac</i>-1,1′-Binaphthalene-2,2′-diol: The Inclusion of an Arylammonium Salt by an Assembly of Binaphthol Groups

Mononuclear copper(i) complexes of triphenylphosphine and N,N′-disubstituted thioureas as potential DNA binding chemotherapeutics

Herein, nine copper(i) bromide complexes with N,N′-disubstituted thioureas and triphenylphosphine, were synthesized via a simple solution-based reaction at 60 °C and characterized, selected complexes were screened for DNA binding.

Hydrogenation reactions catalyzed by HN(CH2CH2PR2)2-ligated copper complexes

Hydrogenation of aldehydes and ketones can be catalyzed by a PNP-ligated copper hydride that is accessible from the copper borohydride or bromide complex or the copper hydride cluster.

Terpyridine based ReX(CO)3 compounds (X = Br–, N3– and triazolate): Spectroscopic and DFT studies

[ReX(CO)3(L–k2N1,N2)] (L = 4′-(4-phenyl morpholine)-2,2′:6′,2′'-terpyridine, X = Br– (1), N3– (2), and triazolate (3)) complexes were synthesized, and characterized using different spectroscopic and analytical tools including single-crystal X-ray diffraction analysis of 2. The 1,3-dipolar cycloaddition reaction between 2, and 4,4,4-trifluoro-2-butynoic acid ethyl ester afforded triazolate 3. Although, the crystal structure of 2 showed that the azide ligand is terminally coordinated to Re(CO)3+ unit, the 19F and 1H NMR analyses of 3 provided conversant evidences that the kinetically formed N(1) triazolate bound isomer favoured the isomerization to N(2) form. The photophysical properties of 1–3 were investigated by recording the absorption spectra of the compounds in solvents of different polarities. Complexes 1 and 3 were screened for their potential antimicrobial activities. The protein binding affinity of 1, and 3 towards hen white egg lysozyme revealed that the bromide complex exchanges Br– with that protein, while the triazolate analogue sticked around.

Synthesis and structural characterisation of some mononuclear 1:1:1 complexes of coinage metal(I) compounds with tertiary phosphines (arsines) and 1,2-diamines, [MX(EPh3)(N,N'-1,2-diamine)

Crystallization of adducts of simple copper(I) and silver(I) salts (MX) with triphenylphosphine from 'N,N,N′,N'-tetramethylethylenediamine', 'tmeda', has yielded adducts of 1:1:1 MX:PPh3:tmeda stoichiometry, all of which have been characterized by room temperature single crystal X-ray structure determinations. In all adducts, the complex is mononuclear [M(PPh3)(N,N′-tmeda)X] with four-coordinate N2PMX metal atom environments (M = Cu, X = Cl, Br, I; M = Ag, X = Cl or NO3). The tricyclohexylphosphine species [Ag(Pcy3)(N,N′-tmeda)(ONO2)], also in a N2PAgX metal environment, has been defined. A number of similar silver(I) adducts are obtained by using 1,2-diaminopropane, 'pn' as solvent. The chloride, bromide and iodide complexes are isomorphous, the complexes being mononuclear, [Ag(PPh3)(pn)X], with four-coordinate N2PAgX environments, the pn ligand chelating. An isomorphous arsenic analogue of the bromide has also been isolated. All complexes have been characterized by IR and NMR (1H and 31P) spectroscopy.

Spectroscopic and electrochemical study of interactions between DNA and different salts of 1,4-dihydropyridine AV-153.

1,4-dihydropyridines (1,4-DHP) possess important biochemical and pharmacological properties, including antimutagenic and DNA-binding activity. The latter activity was first described for water-soluble 1,4-DHP with carboxylic group in position 4, the sodium salt of the 1,4-DHP derivative AV-153 among others. Some data show the modification of physicochemical properties and biological activities of organic compounds by metal ions that form the salts. We demonstrated the different affinity to DNA and DNA-protecting capacity of AV-153 salts, depending on the salt-forming ion (Na, K, Li, Rb, Ca, Mg). This study aimed to use different approaches to collate data on the DNA-binding mode of AV-153-Na and five other AV-153 salts. All the AV-153 salts in this study quenched the ethidium bromide and DNA complex fluorescence, which points to an intercalation binding mode. For some of them, the intercalation binding was confirmed using cyclic voltammetry and circular dichroism spectroscopy. It was shown that in vitro all AV-153 salts can interact with four DNA bases. The FTIR spectroscopy data showed the interaction of AV-153 salts with both DNA bases and phosphate groups. A preference for base interaction was observed as the AV-153 salts interacted mostly with G and C bases. However, the highest differences were detected in the spectral region assigned to phosphate groups, which might indicate either conformational changes of DNA molecule (B form to A or H form) or partial denaturation of the molecule. According to the UV/VIS spectroscopy data, the salts also interact with the human telomere repeat, both in guanine quadruplex (G4) and single-stranded form; Na and K salts manifested higher affinity to G4, Li and Rb –to single-stranded DNA.

Structures and Chemical Bonding in Antimony(III) Bromide Complexes with Pyridine.

Weakly or "partially" bonded molecules are an important link between the chemical and van der Waals interactions. Molecular structures of six new SbBr3 -Py complexes in the solid state have been determined by single-crystal X-ray diffraction analysis. In all complexes all Sb atoms adopt a pseudo-octahedral coordination geometry which is completed by additional Sb⋅⋅⋅Br contacts shorter than the sum of the van der Waals radii, with Br-Sb⋅⋅⋅Br angles close to 180°. To reveal the nature of Sb-Br and Sb-N interactions, the DFT calculations were performed followed by the analysis of the electrostatic potentials, the orbital interactions and the topological analysis. Based on Natural Bond Orbital (NBO) analysis, the Sb-Br interactions range from the covalent bonds to the pnictogen bonds. A simple structural parameter, non-covalence criterion (NCC) is defined as a ratio of the atom-atom distance to the linear combination of sums of covalent and van der Waals radii. NCC correlates with E(2) values for Sb-N, Sb-Cl and Sb-Br bonds, and appears to be useful criterion for a preliminary evaluation of the bonding situation.

Interaction with Simple Monopyridinecarboxylic Ligands Revealing Unexpected Structural Types of Uranyl Halides.

The inclusion of monopyridinecarboxylic acids into the structures of uranyl halides results in the formation of unexpected structural units. Molecules of picolinic and nicotinic acids acting as bridging ligands favor the formation of unprecedented dinuclear units in two uranyl bromide complexes, which comprise two metal centers in different, tetragonal- and pentagonal-bipyramidal, coordination geometries. Moreover, the different positions of the nitrogen atom in the molecule of nicotinic acid induce significant bending of the heterodimer. The uranyl chloride complex with isonicotinic acid also exhibits a structure containing metal atoms in two unique geometries. The structure consists of cationic and anionic isolated fragments. The anionic part is unprecedented and represents the first example of a 1:3 uranyl halide unit with a tetragonal bipyramid surrounding the central atom.

Mononuclear silver(I)-N-heterocyclic carbene complexes with benzimidazole-2-ylidene ligands: synthesis, crystal structure analyses and comparative antibacterial studies

The synthesis, characterization and antibacterial studies of N-heterocyclic carbene (NHC) precursors and their respective silver(I)-NHC complexes are reported. Five non-symmetric benzimidazolium bromide salts were synthesized through the addition of N-alkylbenzimidazole and various alkylbromides. These n-butyl-n’-alkylbenzimidazolium bromide salts (alkyl = methyl, ethyl, pentyl, hexyl, heptyl) 1, 2 and 4–6 were further used as precursors to synthesize silver(I)-NHC complexes, 8, 9 and 11–13, respectively, via in situ deprotonation. In addition, 14 was synthesized from its reported precursor salt, 1-benzyl-3-butylbenzimidazolium bromide (7) through the same procedure. Complex 8 is present as monomeric cation in the form of [NHC-Ag-NHC]PF6, as illustrated by single crystal X-ray crystallography analyses. In order for a full series of antibacterial studies, 1-butyl-3-propylbenzimidazolium bromide, 3, and respective complex, 9, were synthesized according to the reported procedure. All benzimidazolium salts (1–7) and silver(I)-NHC complexes (8–14) were evaluated for antibacterial activities. All benzimidazolium salts show no antibacterial activities while all silver(I)-NHC complexes show lower activities against Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 12600) compared to the standard antibiotic drug Amoxicillin. Nevertheless, these mononuclear silver(I)-NHC complexes show lower antibacterial activities compared to the reported dinuclear silver(I)-NHC complexes with the same substituents in the ligands.

Synthesis, characterization, antifungal and antibacterial activities evaluation of copper (II), zinc (II) and cadmium (II) chloride and bromide complexes with new (E)‐1‐(3,4‐dimethoxybenzylidene)‐4‐methylthiosemicarbazone ligand

The reactions of Cu (II), Zn (II) and Cd (II) chloride or bromide with (E)‐1‐(3,4‐dimethoxybenzylidene)‐4‐methylthiosemicarbazone (MTSVT) lead to the formation of new complexes. They were characterized by spectroscopic studies: IR, 1H and 13C NMR. The crystal structures of the compounds [MTSVT] (L), [ZnBr2(MTSVT)2] (2), [CdCl2(MTSVT)2] (3) and [CdBr2(MTSVT)2.H2O] (4) were determined by X‐ray diffraction. For complexes 2–4, the ion is coordinated through the sulfur atom. All compounds were tested for their antifungal activity against human pathogenic fungi Candida albicans and Aspergillus fumigatus, and for their antibacterial activity against Gram (+) Bacillus subtilis and Enterococcus faecalis as well as against Gram (−) bacteria such as Paracoccus yeei and Acinetobacter baumanii. The results indicated that the metal complexes exhibited a marked enhancement in antibacterial activity compared with the parent Schiff base.

Perovskite-Inspired High Stability Organometal Antimony(V) Halide Thin Films by Post-Deposition Bromination

Metal–organic or all-inorganic Sb(V) bromide complexes are a novel class of semiconductor materials with potential use in optoelectronic devices. The implementation of these materials for optoelect...

Hydrogen and Halogen Bond Mediated Coordination Polymers of Chloro-Substituted Pyrazin-2-Amine Copper(I) Bromide Complexes

A new class of six mono- (1; 3-Cl-, 2; 5-Cl-, 3; 6-Cl-) and di-(4; 3,6-Cl, 5; 5,6-Cl-, 6; 3,5-Cl-) chloro-substituted pyrazin-2-amine ligands (1–6) form complexes with copper (I) bromide, to give 1D and 2D coordination polymers through a combination of halogen and hydrogen bonding that were characterized by X-ray diffraction analysis. These Cu(I) complexes were prepared indirectly from the ligands and CuBr2 via an in situ redox process in moderate to high yields. Four of the pyrazine ligands, 1, 4–6 were found to favor a monodentate mode of coordination to one CuI ion. The absence of a C6-chloro substituent in ligands 1, 2 and 6 supported N1–Cu coordination over the alternative N4–Cu coordination mode evidenced for ligands 4 and 5. These monodentate systems afforded predominantly hydrogen bond (HB) networks containing a catenated (μ3-bromo)-CuI ‘staircase’ motif, with a network of ‘cooperative’ halogen bonds (XB), leading to infinite polymeric structures. Alternatively, ligands 2 and 3 preferred a μ2-N,N’ bridging mode leading to three different polymeric structures. These adopt the (μ3-bromo)-CuI ‘staircase’ motif observed in the monodentate ligands, a unique single (μ2-bromo)-CuI chain, or a discrete Cu2Br2 rhomboid (μ2-bromo)-CuI dimer. Two main HB patterns afforded by self-complimentary dimerization of the amino pyrazines described by the graph set notation R22(8) and non-cyclic intermolecular N–H∙∙∙N’ or N–H∙∙∙Br–Cu leading to infinite polymeric structures are discussed. The cooperative halogen bonding between C–Cl∙∙∙Cl–C and the C–Cl∙∙∙Br–Cu XB contacts are less than the sum of the van der Waals radii of participating atoms, with the latter ranging from 3.4178(14) to 3.582(15) Å. In all cases, the mode of coordination and pyrazine ring substituents affect the pattern of HBs and XBs in these supramolecular structures.