Luminescence and thermal behavior by simultaneous TG/DTG–DTA coupled with MS of neutral copper (I) complexes with heterocyclic thiones

Copper(I) halide complexes formulated as [(L)CuX(μ₂-L)₂CuX(L)] (X = Cl, Br and L = pyridine-2-thione (py2SH), or 4,6-dimethylpyrimidine-2-thione (dmpymtH)) were prepared, and their photoluminescence and thermal properties were investigated. The complexes are strongly emissive in the solid state, with the emissions being dominated by large Stokes shifts (>200 nm), which are depending on both the heterocyclic thione and the nature of the halogen. These emissions can be assigned to MLCT with some mixing of the halide-to-ligand (XL) CT characters. Simultaneous TG/DTG–DTA technique, coupled with MS for the analysis of the gaseous decomposition products, was used for two complexes with the dmpymtH ligand to determine their thermal degradation, which was found to be very complicated. In inert atmosphere the residues at 1,000 °C (verified with PXRD) were a mixture of Cu₂S and CuX, while at 1,300 °C a mixture of Cu₂S and Cu. In oxygen atmosphere the residues were CuO.     

Luminescence and thermal behavior of copper (I) complexes with heterocyclic thiones. Part II: cationic complexes

Copper (I) halide complexes formulated as [(L)₂Cu(μ₂-L)₂Cu(L)₂]²⁺ 2Χ⁻, (X = Cl, Br and L = pyridine-2-thione (py2SH) or 4,6-dimethylpyrimidine-2-thione (dmpymtH)) were prepared, and their photoluminescence and thermal properties were investigated. The complexes are strongly emissive in the solid state, with the emissions being dominated by large Stokes shifts (>200 nm), which are depending on both the heterocyclic thione and the nature of the halogen. These emissions can be assigned to MLCT with some mixing of the halide-to-ligand (XL) CT characters. Simultaneous TG/DTG–DTA technique was used for two complexes with the dmpymtH ligand to determine their thermal degradation, which was found to be very complicated. In inert atmosphere the residues at 1,000 °C (verified with PXRD) were mainly Cu₂S, while at 1,300 °C a mixture of Cu₂S and Cu. In oxygen atmosphere the residues were CuO.     

Syntheses, Structures, and Nonlinear Optical Properties of Two Crown-like Heteroselenometallic Compounds [Et4N]4[(μ5-WSe4)(CuX)5(μ-X)2] (X = Cl, Br)

Two isostructural crown-like heteroselenometallic cluster compounds, [Et₄N]₄[(μ₅-WSe₄)(CuX)₅(μ-X)₂] (X = Cl 1, Br 2), were prepared from the reactions of [Et₄N]₂[WSe₄] with CuX and [Et₄N]X· xH₂O in the presence of 2-picoline and characterized by single-crystal diffraction analysis. The [(μ₅-WSe₄)(Cu-X)₅(μ-X)₂]⁴⁻ anions in the cluster compounds consists of five CuX fragments coordinated to the five edges of the tetrahedral [WSe₄]²⁻ moiety along with two bridging halides connected to each of the two pairs of the symmetric copper atoms, exhibiting a novel crown-like core structure. The nonlinear optical absorption and refraction of cluster compound 2 were determined to be α₂ = 6.15 × 10⁻¹⁰ m/W and n ₂ = 4.18 × 10⁻¹¹ esu, respectively.     

Synthesis,structural characterization and substituent effects of two copper(II) complexes with benzaldehyde ortho-oxime ligands

Two new Cu(II) complexes, [Cu(L¹)₂] (1) and [Cu(L²)₂] (2) (HL¹ = (E)-3-bromo-5-chloro-2-hydroxy benzaldehyde O-methyl oxime; HL² = (E)-3-bromo-5-chloro-2-hydroxy benzaldehyde O-ethyl oxime), have been synthesized and characterized by physicochemical and spectroscopic methods. X-ray crystallographic analyses show that complexes 1 and 2 have similar structures, consisting of one Cu(II) atom and two L⁻ units. In both complexes, the Cu(II) atom, lying on an inversion center, is four-coordinated in a trans-CuN₂O₂ square-planar geometry by two phenolate O and two oxime N atoms from two symmetry-related N,O-bidentate oxime ligands. Moreover, both complexes form an infinite three-dimensional supramolecular structure involving intermolecular C–H···Br hydrogen bonds and π···π stacking interactions between the metal chelate rings and aromatic rings. Substituent effects in the two complexes are discussed.     

Thermogravimetric evaluation of decomposition kinetics of metal surfactant complexes

Thermal behavior of various synthesized transition metal surfactant complexes of the type [M(CH₃COO)₄]²⁻[C₁₂H₂₅NH₃ ⁺]₂ where M: Cu(II), Ni(II), Co(II) has been investigated using Thermogravimetric Analysis (TGA). It was found that pyrolytic decomposition occurs with melting in metal complexes, and that metal oxides remain as final products. The activation energy order obtained, E _Cu > E _Ni > E _Co, could be explained on the basis of size of transition metal ion and metal ligand bond strength. In the course of our investigation on the decomposition of complexes, we carried out a comparative study of different measurement and calculation procedures for the thermal decomposition. A critical examination was made of the kinetic parameters of non-isothermal thermoanalytic rate measurement by means of several methods such as Coats–Redfern (CR), Horowitz–Metzger (HM), van Krevelen (vK), Madhusudanan–Krishnan–Ninan (MKN), and Wanjun–Yuwen–Hen–Cunxin (WYHC). The most appropriate method among these was determined for each decomposition step according to the least-squares linear regression. It was found that the results obtained using CR method differ considerably from HM method, as the former method involves a lot of approximations and is not much reliable. The application of thermoanalytic techniques to the investigation of rate processes has also been discussed.     

Synthesis and properties of the Cu(II) complexes with chiral bis{( E )-[(1 S ,4 R )-Δ7,8-1-amino-2- para -menthalidene]aminohydroxy}methane (L — a derivative of natural terpenoid ( R )-(+)-limonene). Crystal structure of the [Cu(L)(μ-Cl)CuCl3] · iso -PrOH solvate

The Cu₂LCl₄ complex (I) with chiral bis{(E)-[(1S,4R)-Δ^7,8-1-amino-2-para-menthalidene]aminohydroxy} methane (L — a derivative of natural monoterpenoid (R)-(+)-limonene) is synthesized. The crystal structure of the solvate of complex I[Cu(L)(μ-Cl)CuCl₃] · iso-PrOH (II) is determined by X-ray diffraction analysis. Structure II is based on molecules of the [Cu(L)(μ-Cl)CuCl₃] binuclear complexes in which L is the tetradentate cycleforming ligand. One Cl atom manifests the bridging function. The CuN₄ Cl coordination unit is a square pyramid, and CuCl₄ is a distorted tetrahedron. The iso-PrOH molecules are localized in cavities between the layers of structure II. The μ_eff value for complex I is 2.56 μB and indicates the absence of an appreciable interaction between the Cu²⁺ ions in the Cu(II)-Cl-Cu(II) exchange cluster. The compound CuLCl₂· H₂O (III) is synthesized. The μ_eff value for compound III is 1.6 μB. Complexes I and III are studied by EPR and IR spectroscopy. Original Russian Text ? T.E. Kokina, L.A. Glinskaya, R.F. Klevtsova, E.G. Boguslavskii, L.A. Sheludyakova, S.N. Bisyaev, A.V. Tkachev, S.V. Larionov, 2009, published in Koordinatsionnaya Khimiya, 2009, Vol. 35, No. 3, pp. 202–211.     

Synthesis and structures of copper(I) and cobalt(III) dimers with the dicyano-acetic acid methyl ester anion derived from TCNE

In the presence of CoCl₂ · 6H₂O or CuCl, the reaction of tetracyanoethylene and CH₃OH provides a dicyano-acetic acid methyl ester anion (L1), which has been obtained as a bridged ligand in two compounds [(PPh₃)₂(NC)₂Co^III(μ₂-L1₂)Co^III(CN)₂(PPh₃)₂] · (PPh₃)(CH₃OH) 1 and [(PPh₃)₂Cu^I(μ₂-L1₂)Cu^I(PPh₃)₂] 2. The coordination geometry of the Co atom in 1 is distorted octahedral, and the Co atoms are μ₂-bridged by two pairs of L. For compound 2, Cu is coordinated with two P atoms from PPh₃ and two N atoms of L1, and two Cu atoms are linked by μ₂-bridged L1. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Syntheses,molecular structures and magnetic properties of two hybrid organic–inorganic salts of bis(maleonitriledithiolato)copper(II) and substituted benzyl-4-dimethylaminopyridinium cations

Two new hybrid organic–inorganic salts, [BzDMAP]₂[Cu(mnt)₂](1) and [NO₂BzDMAP]₂[Cu(mnt)₂] (2) ([BzDMAP]⁺ = 1-benzyl-4′-dimethylaminopyridinium, [NO₂BzDMAP]⁺ = 1-(4′-nitrobenzyl)-4′-dimethylaminopyridinium, and mnt²⁻ = maleonitriledithiolate) have been characterized structurally and magnetically. The [BzDMAP]⁺ or [NO₂BzDMAP]⁺ cations (C) and the [Cu(mnt)₂]²⁻ anions (A) in 1 and 2 stack into a 1D alternating CC-A-CC-A-CC column. The Cu···N, π···π, C–H···N, C–H···O, and C–H···S weak interactions play important roles in the molecular stacking and generate a 2D or 3D structure of 1 and 2. The magnetic susceptibilities of these salts measured in the temperature range 2.0–300 K show weak antiferromagnetic coupling features with θ = −2.370 K for 1 and −0.222 K for 2.     

Recent studies on chemistry of novel μ-CO-containing butterfly Fe/E (E=S,Se,Te) cluster salts

This article describes recent developments in chemical study on a series of butterfly-shaped μ-CO-containing Fe/E (E = S, Se, Te) cluster salts. These salts include eleven novel cluster anions, which are the single butterfly one μ-CO-containing [(μ-RE)(μ-CO)Fe2(CO)6]- (A), the double butterfly two μ-CO-containing {[(μ-CO)Fe2(CO)6]2(μ-EZE-μ)}2- (B, E = S; C, E = Se), the triple butterfly three μ-CO- containing {[(μ-CO)Fe2(CO)6]3[(μ-SCH2CH2)3N]}3- (D), {[(μ-CO)Fe2(CO)6]3[1,3,5-(μ-SCH2)3C6H3]}3- (E), {[(μ- CO)...     

Syntheses and Crystal Structures of Polynuclear Cu(I) Complexes Containing the 1,1′-Bis-(diphenylphosphino)-ferrocene Ligand

Summary.  The reaction between [Cu(NCMe)₄][PF₆] and 1,1′-bis-(diphenylphosphino)-ferrocene (dppf) in several ratios, solvents, and conditions led to the synthesis and structural characterization of the Cu(I) complexes [Cu(dppf)(Odppf)][PF₆] (1), [(dppf)Cu(μ-dppf)Cu(dppf)][PF₆]₂ (2), and [(dppf)Cu(μ-Cl)₂Cu(dppf)] (3). Although 1 and the cation in 2 were known, the first was structurally characterized for the first time, exhibiting a significant asymmetry in the coordination sphere of Cu(I) owing to the presence of oxygen. In 2, the PF₆ ⁻ anion led to an interesting crystal packing with large open channels containing water. Finally, DFT calculations on a model of 3 showed that its HOMO exhibits, besides Fe, a significant Cu and Cl character, which is reflected in its electrochemical properties. Received July 14, 2000. Accepted July 21, 2000     

Crystal structure and magnetic properties of a three-dimensional complex constructed from [CuL]2+ and [Fe(CN)6]3− precursors

Self-assembly of the precursor [Cu(L)]²⁺ (L = 3,10-dipropyl-1,3,5,8,10,12-hexaazacyclotetradecane) with hexacyanometalate [Fe(CN)₆]³⁻ produces a 3-D cyano-bridged Cu(II)–Fe(III) bimetallic assembly, [CuL]₂[Fe(CN)₆]ClO₄ · H₂O (1), characterized by single-crystal X-ray diffraction studies, and magnetic measurements. The crystallographic determination reveals that each hexacyanoferromate(III) ion connects four copper(II) ions using four co-planar CN⁻ groups which axially coordinate to the copper ion in a trans fashion forming trans-CuL(N≡C)₂ moieties in (1). Magnetic studies reveal that (1) displays a ferromagnetic interaction between Cu(II) and Fe(III) through the CN linkage.     

A Series of 1-D Lanthanide Coordination Polymers Based on [Ln4(μ3-OH)4] (Ln = Er, Tb, Gd) Cluster Units

Abstract  

A series of 1-D lanthanide coordination polymers [Ln(μ₃-OH)(pybz)(pa)] _n (Ln = Er (1), Tb (2), Gd (3), Hpybz = 4-pyridin-4-yl-benzoic acid, Hpa = 2-picolinic acid) based on [Ln₄(μ₃-OH)₄] cluster units have been hydrothermally synthesized and characterized by single crystal X-ray diffraction, IR, elemental analysis, and thermogravimetric analysis. X-ray crystal structure analyses reveal that 1–3 are isomorphous with tetragonal space group P [`4] \overline{4} 2₁c and comprise tetranuclear Ln–O clusters, in which four Ln³⁺ centers are joined together by four μ₃-bridging hydroxyl groups to form cubane-like [Ln₄(μ₃-OH)₄]⁸⁺ cores that are further linked by four μ₃-pa⁻ ligands to produce 1-D chains along the c-axis.     

Kinetics of the Reactions between [(RS)2Fe(µ-S)2M(µ-S)2Fe(SR)2] n− (M = Mo, R = Ph, n = 2; M = V, R = Et, n = 3) and [Fe(SR)4]2−: Key Steps in the Assembly of Cuboidal Fe—S-based Clusters

The reaction of [S₂Mo(μ-S)₂Fe(SPh)₂]²⁻ with [Fe(SPh)₄]²⁻ produces the dicuboidal cluster [{MoFe₃S₄(SPh)₃}₂(μ-(SPh)₃]³⁻ in a three stage process studied by ¹H-n.m.r. spectroscopy and stopped-flow spectrophotometry. The initial stage involves the formation of the linear trinuclear [(PhS)₂Fe(μ-S)₂Mo(μ-S)₂Fe(SPh)₂]²⁻ and the kinetics indicate an equilibrium reaction (k₁^Mo = 2.5±0.3x 10² dm³ mol⁻¹ s⁻¹, k₋₁^Mo = 0.8±0.1 s⁻¹). The second stage involves the reduction of [(PhS)₂Fe(μ-S)₂Mo(μ-S)₂Fe(SPh)₂]²⁻ by [Fe(SPh)₄]²⁻ to form [(PhS)₂Fe(μ-S)₂Mo(μ-S)₂Fe(SPh)₂]³⁻ which subsequently rearranges to form the voided cuboidal [MoFe₂S₄(SPh)₃]²⁻. The kinetics of the second stage exhibits a simple first order dependence on the concentrations of both [(PhS)₂Fe(μ-S)₂Mo(μ-S)₂Fe(SPh)₂]³⁻ and [Fe(SPh)₄]²⁻ (k₂^Mo = 25 ± 2 dm³ mol⁻¹ s⁻¹). The Kinetics of the third stage have not been studied but must involve incorporation of the final Fe and formation of the dicuboidal [{MoFe₃S₄(SPh)₃}₂(μ-SPh)₃]³⁻. The kinetics of the reaction between [(EtS)₂Fe(μ-S)₂V(μ-S)₂Fe(SEt)₂]³⁻ and [Fe(SEt)₄]²⁻ to form [{VFe₃S₄(SEt)₃}₂(μ-SEt)₃]³⁻ have also been studied. An important difference between this reaction and the formation of the analogous [{MoFe₃S₄(SPh)₃}₂(μ-SPh)₃]³⁻ is that the formation of [{MoFe₃S₄(SPh)₃}₂(μ-SPh)₃]³⁻ from [(PhS)₂Fe(μ-S)₂Mo(μ-S)₂Fe(SPh)₂]²⁻ involves a change in the redox state of the cluster, whilst the formation of [{VFe₃S₄(SEt)₃}₂(μ-SEt)₃]³⁻ from [(EtS)₂Fe(μ-S)₂V(μ-S)₂Fe(SEt)₂]³⁻ requires no change in redox state. The reaction between [(EtS)₂Fe(μ-S)₂V(μ-S)₂Fe(SEt)₂]³⁻ and [Fe(SEt)₄]²⁻ involves two stages. The kinetics of the faster phase is associated with a rate law analogous to that observed for the reaction between [(PhS)₂Fe(μ-S)₂Mo(μ-S)₂ Fe(SPh)₂]²⁻ with [Fe(SPh)₄]²⁻: a first order dependence on the concentrations of [(EtS)₂Fe(μ-S)₂V(μ-S)₂Fe(SEt)₂]³⁻ and [Fe(SEt)₄]²⁻ (k₂^V = 1.1±0.1 x 10³ dm³ mol⁻¹ s⁻¹. This observation indicates that whilst there is no change in redox state between [(EtS)₂Fe(μ-S)₂V(μ-S)₂Fe(SEt)₂]³⁻ and [{VFe₃S₄(SEt)₃}₂(μ-SEt)₃]³⁻, reduction is necessary to catalyse the conversion of the linear [(EtS)₂Fe(μ-S)₂V(μ-S)₂Fe(SEt)₂]³⁻ into the voided cuboidal [VFe₂S₄(SEt)₃]³⁻. The results of the studies reported in this paper together with those on other putative reactions involved in the assembly of cuboidal clusters, have been combined to present a scheme of the mechanism of cuboidal cluster assembly. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

Synthesis,crystal structures,and antibacterial activities of two copper(II) complexes derived from 1-[(2-morpholin-4-ylethylimino)methyl]-naphthalen-2-ol

A trinuclear complex, [Cu(Cu(μ-Br)₂L)₂], and a dinuclear complex, [Cu₂(μ-Cl)₂L₂], have been synthesized with the tridentate Schiff base 1-[(2-morpholin-4-ylethylimino)methyl]-naphthalen-2-ol (HL), derived from 2-hydroxy-1-naphthyaldehyde and 4-(2-aminoethyl)morpholine. Both complexes have been characterized by physicochemical and spectroscopic methods. [Cu(Cu(μ-Br)₂L)₂] is a centrosymmetric bromide and phenolate oxygen-bridged trinuclear compound, while complex [Cu₂(μ-Cl)₂L₂] is a centrosymmetric-chloride-bridged dinuclear compound. The central Cu(II) atom in [Cu(Cu(μ-Br)₂L)₂] is six-coordinated in an octahedral coordination, while other Cu(II) atoms in both complexes are five-coordinated in square-pyramidal coordinations. Both complexes and HL were tested in vitro for their antibacterial activities.     

Structure of complex salts [Co(NH3)6][Rh(NO2)6] and [Co(NH3)6][(NO2)3Rh(μ-NO2)1+x(μ-OH)2?xRh(NO2)3]·(2-x)(H2O), x = 0.17

The structures of two salts [Co(NH₃)₆][Rh(NO₂)₆] (I) and [Co(NH₃)₆][(NO₂)₃Rh(μ-NO₂)_1+x (μ-OH)_2−x Rh(NO₂)₃]·(2−x)(H₂O), x = 0.17 (II) are solved. Single crystals of the salts are obtained by the counter diffusion method through the gel of aqueous solutions of [Co(NH₃)₆]Cl₃ and Na₃[Rh(NO₂)₆]. The structure of [Co(NH₃)₆][Rh(NO₂)₆] is consistent with the diffraction data for a polycrystalline sample of poorly soluble fine salt formed in the exchange reaction between aqueous solutions of [Co(NH₃)₆]Cl₃ and Na₃[Rh(NO₂)₆]. The structure of [Co(NH₃)₆][(NO₂)₃Rh(μ-NO₂)_1+x (μ-OH)_2−x Rh(NO₂)₃]·(2−x)(H₂O), x = 0.17 exhibits the stabilizing effect of a large cation in the formation of novel, unknown previously coordination ions: [(NO₂)₃Rh(μ-NO₂)(μ-OH)₂Rh(NO₂)₃]³⁻ and [(NO₂)₃Rh(μ-NO₂)₂(μ-OH)Rh(NO₂)₃]³⁻.     

Electrospray Ionization Based Methods for the Generation of Polynuclear Oxo- and Hydroxo Group 6 Anions in the Gas-Phase

Electrospray ionization (ESI) of the Lindqvist (n-Bu₄N)₂[M₆O₁₉] (M = Mo, W) polyoxometalates provides a straightforward entry for the generation of an assortment of oxo- and hydroxo anions in the gas-phase. In particular, the series of oxo dianions of general formula [(MO₃) _n O]²⁻ (n = 2–6; M = Mo, W), monoanions, namely [(MO₃) _n O]⁻ (n = 1, 2) and [(MO₃) _n ]⁻ (n = 1, 2), and the hydroxo [(MO₃) _n (OH)]⁻ (n = 1–6) species can be readily generated in the gas-phase upon varying the solvent composition as well as the ionisation conditions (typically the U_c cone voltage). Complementary tandem mass experiments (collision induced dissociation and ion–molecule reactions) are also used aimed to investigate the consecutive dissociation of these species and their intrinsic gas-phase reactivity towards methanol. Special emphasis is paid to some of the key factors of these group 6 anions related to the gas-phase activation of methanol, such as molecular composition, open vs closed shell electronic nature and cluster size.     

Synthesis and characterization of stable thiazolylazo anion radical complexes of ruthenium(II)

Two stable thiazolylazo anion radical complexes of ruthenium(II), [Ru(L1^•−)(Cl)(CO)(PPh₃)₂] (1) and [Ru(L2^•−)(Cl)(CO)(PPh₃)₂] (2) (where L1 = 2′-Thiazolylazo-2-imidazole and L2 = 4-(2′-Thiazolylazo)-1-n-hexadecyloxy-naphthalene), have been synthesized and characterized by spectroscopic and electrochemical techniques. The radical nature of the complexes has been confirmed from their room temperature magnetic moments and X-band ESR spectra. The radical complexes display a moderately intense (ε ~ 10⁴ M⁻¹ cm⁻¹) and relatively broad band in 430–460 nm region. In the microcrystalline state, complexes (1) and (2) display strong ESR signals at g = 1.951 and g = 1.988, respectively. In CH₂Cl₂ solution, complexes (1) and (2) show a quasireversible one-electron response near −0.64 and −0.59 V, respectively, versus Ag/AgCl due to the radical redox couple [Ru^II(L)(Cl)(CO)(PPh₃)₂]/[Ru^II (L^•−)(Cl)(CO)(PPh₃)₂].     

Thiolate-bridged Trinuclear Heterobimetallic Complexes [Cd(μ-SPh-4-Me)4{M(PPh3)2}2] (M?=?Cu, Ag) and [Sn(μ-SPh)6(AgPPh3)2]

Abstract  

Reaction of the [Me₄N]₂[Cd(SPh-4-Me)₄] with two equivalents of [M(PPh₃)₂NO₃] afforded the neutral linear trinuclear complexes [Cd(μ-SPh-4-Me)₄{M(PPh₃)₂}₂] (M = Cu 1, Ag 2) in which two [M(PPh₃)₂]⁺ fragments chelate with the opposite edges of a tetrahedral [Cd(SPh-4-Me)₄]²⁻ moiety via the sulfur atoms of the Me-4-PhS⁻ species. Treatment of [Sn(SPh)₄] with two equivalents of [Ag(PPh₃)₂NO₃] gave the neutral linear trinuclear complex [Sn(μ-SPh)₆(AgPPh₃)₂] (3) that is composed of a central distorted SnS₆ octahedron sharing two opposite planes with two slightly distorted AgS₃P tetrahedrons. Complexes 2 and 3 are air and optically stable. Their nonlinear optical absorption and refraction were investigated under the same conditions. The nonlinear optical absorption and refraction of complex 2 were determined to be α ₂ = 3.11 × 10⁻¹¹ m/W and n ₂ = 4.15 × 10⁻¹² esu, respectively. The nonlinear optical absorption and refraction of complex 3 were determined to be α ₂ = 8.36 × 10⁻¹¹ m/W and n ₂ = 1.47 × 10⁻¹¹ esu, respectively.     

A new cobalt complex of 1-decyl-1<Emphasis Type="Italic">H</Emphasis>-benzo[<Emphasis Type="Italic">d</Emphasis>]imidazole: synthesis,characterization and electrocatalysis

The present work reports on the synthesis, characterization and performance of a new cobalt(II) complex, [Co(C₁₀H₂₁-bim)₂(SCN)₂] (bim = benzimidazole) as electrocatalyst for trichloroacetic acid and bromate reduction. Its structure was characterized by X-ray crystallography, IR spectroscopy and elemental analysis. The cobalt atom adopts a distorted tetrahedral geometry by coordinating to four nitrogen atoms from two thiocyanates and two 1-decyl-1H-benzo[d]imidazole ligands. The electrochemical behavior and electrocatalysis of the title complex bulk-modified carbon paste electrode (Co-CPE) have been studied by cyclic voltammetry. The Co-CPE shows good electrocatalytic activities toward the reduction of trichloroacetic acid and bromate. The detection limit and the sensitivity are 0.02 μM, 34.63 μA μM⁻¹ for trichloroacetic acid detection, and 0.03 μM, 78.92 μA μM⁻¹ for bromate detection, respectively. This modified electrode shows good reproducibility, high stability, low detection limit, technical simplicity and possibility of rapid preparation, which is important for practical application.     

Kinetics of oxidation of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-ethylenebis(isonitrosoacetylacetoneimine)copper(II) by peroxydisulfate in aqueous acidic solutions

Peroxydisulfate (PDS) oxidizes N,N′-ethylenebis(isonitrosoacetyleacetoneimine)copper(II) complex, Cu^IIL, to the corresponding copper(III) complex, [Cu^IIIL]⁺. The kinetic runs were performed in the presence of EDTA to scavenge any trace metal impurities. The kinetics of the reaction at constant pH, ionic strength, and temperature obeys the rate law d[Cu^IIIL]/dt = 2k ₂[Cu^IIL][S₂O₈ ²⁻] with k ₂ having a value of (8.85 ± 0.32) × 10⁻² M⁻¹ s⁻¹ at μ = 0.30 M and T = 25.0 °C. The rate constant k ₂ is not affected by variation of pH over the range 3.60–5.20. The second order rate constant is also unaffected by changing ionic strength. The values of k _obs were determined over the temperature 25.0–40.0 °C range. The enthalpy of activation, ∆H*, and entropy of activation, ∆S*, have been calculated as 34.9 ± 0.5 kJ mol⁻¹ and −173.3 ± 11.4 J K⁻¹ mol⁻¹, respectively. The kinetics of this reaction, as far as we know, is the first evidence that copper(III) is the likely reactive species in copper catalyzed PDS oxidation reactions.