Inhibition of two Cu(II) and Mn(II) coordination polymers on the surgical site infections by inhibiting the bacterial biofilm formation

Within this work, two novel Cu(II) and Mn(II)-based coordination polymers (CPs) along with chemical compositions of {[Cu₂(L¹)(1,4-NDC)₂]·3H₂O}_n (1, 1,4-H₂NDC = Naphthalene-1,4-dicarboxylic acid, L¹ ​= ​di(1H-imidazole-1-yl)methane) and [Mn₃(L²)₂(H₂O)₂(1,4-NDC)₂]_n (2, L² ​= ​1,4-di(1H-imidazole-1-yl)benzene) have been completed in success via related metal salts reaction with 1,4-H₂NDC ligand in existence of various N-donor co-ligands. We discovered its application values on the surgical site infections (SSI) along with corresponding mechanism in the interim. We evaluated inflammatory cytokines released into the urine through ELISA detection kit after compound treatment. Then, we discovered the inhibitory effect of compound on the bacterial biofilm formation via real time RT-PCR.     

Photophysical insights on quantum dots-zinc porphyrazine system studied in solution

The present study reports spontaneous interaction of a quantum dots, namely, CdS_xSe_1-x/ZnS (QD) with zinc porphyrazine (1) in toluene. It is observed from steady state fluorescence measurements that photoluminescence of QD suffers quenching by 1. Time resolved fluorescence measurements reveal small change in the lifetime of QD (16.10 ns) following it interaction with 1 (15.77 ns). The magnitude of k_q for QD-1 system, i.e., k_q ​= ​5.25 ​× ​10¹² ​L⋅mol⁻¹⋅sec⁻¹ (evaluated from the stern-volmer plot) establishes that photoexcited QD undergoes decay by 1 according to static quenching mechanism. The results emerging from above study confirm that QD-1 system may be judiciously applied as an energy storage material in near future.     

Synthesis and characterization of penta-coordinated copper(II) complexes with hydrazido based ligand and imidazole as auxiliary ligand

The reaction of (Z)-2-(phenyl(2-(pyridin-2-yl)hydrazono)methyl)pyridine (L) and copper(II) salt in methanol yields a series of five pentacoordinated mononuclear complexes. The molecular formulations of these complexes are as [Cu(L)(ImH)₂](ClO₄)₂ (1), [Cu(L)(2-MeImH)₂](ClO₄)₂ (2), [Cu(L)(2-EthImH)₂](ClO₄)₂ (3), [Cu(L)(BenzImH)₂](ClO₄)₂ (4) and [Cu(L)(2-MeBenzImH)₂](ClO₄)₂ (5) (where ImH ​= ​Imidazole, 2-MeImH ​= ​2-Methylimidazole, 2-EthImH ​= ​2-Ethylimidazole, BenzImH ​= ​Benzimidazole, 2-MeBenzImH ​= ​2-Methylbenzimidazole). The room temperature magnetic moment values are in the range 1.79–1.81 B ​M. The conductance measurements suggest that they are electrolytic in nature. The DFT calculations were performed to get information about the structures of the complexes. The copper(II) centre in all complexes is a Penta-coordinated. The proligand has NNN donor sites viz., two pyridine N and one azomethine N atoms, whereas co-ligand coordinates through pyridine N atom forming two five-membered chelate rings. The τ₅ values of these complexes are in the range 0.177–0.495. Both pro and co-ligands are neutral. X-band Epr spectral measurements have been carried out to authenticate the paramagnetic behaviours of all complexes. The stability of the copper(II) centre was examined using cyclic and differential pulse Voltammetry. The IC₅₀ and SOD activity values for all complexes reveal that they are good SOD active complexes. The IC₅₀ value of present complexes remains in the range 26–43 ​μM.     

Theoretical and experimental study of IR spectra of large phenol-acetylene clusters,Ph(Ac)n for 8 ≤ n ≤ 12

This work reports a combined theoretical and experimental study on large phenol-acetylene clusters, Ph(Ac)_n, 8 ​≤ ​n ​≤ ​12, extending our earlier work on the smaller clusters [Singh, G.; Nandi, A.; Gadre, S. R.; Chiba, T.; Fujii, A. J. Chem. Phys. 2017, 146, 154303]. Several trial cluster geometries are generated using the molecular electrostatic potential (MESP) for placing additional acetylene moieties, followed by geometry optimization at B97D/aug-cc-pVDZ level theory. The infrared spectra of energetically low-lying (within 0.5 ​mH window) isomers of the clusters are calculated and averaged. The O–H stretching band shows two peaks due to the presence of energetically close isomers differing in the arrangement of acetylenes around the O–H group. The acetylenic C–H stretching band appears around 3260 ​cm⁻¹. The C–H band shows a red shift of about 3 ​cm⁻¹ on going from n ​= ​8 to 12. Moderately size-selected IR spectra of Ph(Ac)_n (n ​= ​~10 and ~13) prepared by a supersonic jet expansion are measured for the acetylenic C–H region by infrared-ultraviolet double resonance spectroscopy combined with time-of-flight mass spectrometry. The observed spectral features are in agreement with the trends of the frequency shift and asymmetric line shape of the C–H stretch band predicted by the theoretical calculations.     

Dinuclear nickel(II) complexes with Schiff base ligands: syntheses, structures and bio-relevant catalytic activities

Three Ni(II) complexes of cresol-based Schiff-base ligands, namely [Ni₂(L¹)(NCS)₃(H₂O)₂], (1) [Ni₂(L²)(CH₃COO)(NCS)₂(H₂O)] (2) and [Ni₂(L³)(NCS)₃] (3), (where L¹ = 2,6-bis(N-ethylpyrrolidineiminomethyl)-4-methylphenolato, L² = 2,6-bis(N-ethylpiperidineiminomethyl)-4-methylphenolato and L³ = 2,6-bis{N-ethyl-N-(3-hydroxypropyl iminomethyl)}-4-methylphenolato), have been synthesized and structurally characterized by X-ray single-crystal diffraction in addition to routine physicochemical techniques. Density functional theory calculations have been performed to understand the nature of the electronic spectra of the complexes. Complexes 1?C3 when reacted with 4-nitrophenyl phosphate in 50:50 acetonitrile?Cwater medium promote the cleavage of the O?CP bond to form p-nitrophenol and smoothly convert 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylquinone (3,5-DTBQ) either in MeOH or in MeCN medium. Phosphatase- and catecholase-like activities were monitored by UV?Cvis spectrophotometry and the Michaelis?CMenten equation was applied to rationalize all the kinetic parameters. Upon treatment with urea, complexes 1 and 2 give rise to [Ni₂(L¹)(NCS)₂(NCO)(H₂O)₂] (1??) and [Ni₂(L²)(CH₃COO)(NCO)(NCS)(H₂O)] (2??) derivatives, respectively, whereas 3 remains unaltered under same reaction conditions.     

Extraction of acephate pesticide in environmental and agricultural samples by spectrophotometric method

In the present study, we have synthesis the azo dye for the reaction of p-amino antipyrine with HCl in NaNO₂ solution a 1:1 ​M ratio that was kept -5°C for 1–2 ​h, as result the absorption spectra observed at λ_max ​= ​460 ​nm. Beer’s law is obeyed over the awareness variety of 1 ​μg–100 ​μg ​mL^-1. The standard deviation and relative well-known deviation are 0.007 and 1.38%. The molar absorptivity and Sandell's sensitivity had been located to be 0.98 ​× ​10⁵ ​L ​mol^-1 ​cm^-1 and 0.99 ​× ​10^-3 ​μg ​cm^-2, respectively. Spectroscopy method used for the detection of Acephate pesticides on vegetable, fruit, soil, and water samples. FTIR method was used to consider and achieve structural information about the presented intermolecular interactions for vegetable samples. The eco-friendliness of the developed methods was assessed using the spectroscopy analytical tool on vegetables, fruit, soil, and water samples.     

A Cu(II) coordination framework constructed by the inorganic layer and a bent dipyridyl ligand: Synthesis,structure and magnetic properties

A new Cu(II) coordination framework {[Cu(4-abpt)(μ₃-SO₄^2-)(H₂O)]·3H₂O}_∞ (1) based on the Cu–SO₄^2- inorganic layer and the bent dipyridyl ligand was obtained under solvothermal conditions (4-abpt ​= ​4-amino-3,5-bis(4-pyridyl)-1,2,4-triazole). The compound displays a three-dimensional (3D) “pillar-layer” framework, which can be simplified into a 3,5-connected gra topology. Furthermore, the magnetic properties of 1 have been investigated. As a result, compound 1 displays a weak antiferromagnetic interaction among the Cu(II) centers.     

Synthesis, structural, spectroscopic and reactivity properties of a new N-2,3,4-trifluorophenyl-3,5-di-tert-butylsalicylaldimine ligand and its Cu(II) and Pd(II) complexes

A new N-2,3,4-trifluorophenyl-3,5-di-tert-butylsalicylaldimine (1) complexes with Cu(II) (2) and Pd(II) (3) have been synthesized and characterized by X-ray crystallography, UV-Vis, IR, ¹H NMR and EPR spectroscopic techniques. The X-ray crystal structure of complex 2 reveals tetrahedrally distorted square-planar coordination geometry around Cu(II). The UV/Vis and EPR results indicate that the solid state geometry of 2 remains unchanged in solutions. Chemical oxidation of 3 with Ce(IV) in CHCl₃ generates relatively stable Pd(II)-phenoxyl radical complex (g = 2.0073). The results related with the chemical oxidation of 2 and 3 as well as the catalytic activity of 3 in the hydrogenation of PhNO₂ are presented.     

Ruthenium(II/III) bipyridine complexes incorporating thiol-based imine functions: Synthesis,spectroscopic and redox properties

A group of five new ruthenium(II) bipyridine heterochelates of the type [Ru^II(bpy)₂L]⁺ 1a–1e have been synthesized (bpy=2,2′-bipyridine; L=anionic form of the thiol-based imine ligands, HS–C₆H₄NC(H)C₆H₄(R) (R=OMe, Me, H, Cl, NO₂). The complexes 1a−1e are 1:1 conducting and diamagnetic. The complexes 1a−1e exhibit strong MLCT transitions in the visible region and intra-ligand transitions in the UV region. In acetonitrile solvent complexes show a reversible ruthenium(III)–ruthenium(II) couple in the range 0.2–0.4 V and irreversible ruthenium(III)→ruthenium(IV) oxidation in the range 1.15–1.73 V vs. SCE. Two successive bipyridine reductions are observed in the ranges −1.43 to −1.57 and −1.67 to −1.78 V vs. SCE. The complexes are susceptible to undergo stereoretentive oxidations to the trivalent ruthenium(III) congeners. The isolated one-electron paramagnetic ruthenium(III) complex, 1c⁺ exhibits weak rhombic EPR spectrum at 77 K (g₁=2.106, g₂=2.093, g₃=1.966) in 1:1 chloroform–toluene. The EPR spectrum of 1c⁺ has been analyzed to furnish values of distortion parameters (Δ=8988 cm⁻¹; V=0.8833 cm⁻¹) and energy of the expected ligand field transitions (ν₁=1028 nm and ν₂=1186 nm) within the t₂ shell. One of the ligand field transitions has been experimentally observed at 1265 nm.     

A comparative catalytic study using different metal ions by incorporating functionalized metallosalen into the lacunary position of Keggin polyoxometalate

A series of new hybrids, POM (M-Salen@POM) were synthesized by successfully inserting metallosalen compounds (where M ​= ​Co, Cu, Fe and Ru) into the lacunary position of Keggin type polyoxometalate, K₈SiW₁₁O₃₉ (POM). The hybrids were characterized by FT-IR, powder XRD, diffuse reflectance UV–Vis, energy dispersive X-Ray and inductively coupled plasma atomic emission spectroscopy (ICP) techniques. The hybrids with different metal centers were comparatively studied for their catalytic activity in the oxidation of cycloalkanes, cycloalcohols and alkyl aromatic using a green oxidant, hydrogen peroxide. The products obtained during catalysis were estimated by gas chromatography(GC) and mass spectroscopy(MS). Catalytically synthesized products are of high industrial importance.     

Tridentate Schiff base and 4,4′-bipyridine coordinated di/polynuclear Cu (II) complexes: Synthesis,crystal structure,DNA/protein binding and catecholase activity

4,4′-bipyridine bridged two Cu (II) complexes, [Cu₂L¹₂(4,4′-bipy)(H₂O)₂](ClO₄)₂ ( 1 ) and [Cu₂L²₂(4,4′-bipy)]_n·(2H₂O)_n ( 2 ) (where, HL¹ = 2-[(3-methylamino-propylimino)-methyl]-phenol, H₂L² = 3-[(2-hydroxy-3-methoxy-benzylidene)-amino]-propionic acid, and 4,4′-bipy = 4,4′-bipyridine) have been synthesized and characterized by single crystal structure determination, mass spectrometry, FT-IR, electronic absorption, and emission spectroscopy. Complex 1 is dinuclear cationic compound and counter balanced by perchlorate anion, whereas complex 2 possesses 1D poly-nuclear structure. Both the complexes crystallize in monoclinic system with P2₁/c space group and the copper centers possess square pyramidal geometry. H-bonding, C-H···π, π···π interactions results the formation of two dimentional supramolecular structure for both the complexes. Interactions of complexes with bovine serum albumins (BSA) and human serum albumins (HSA) have been studied by using electronic absorption and emission spectroscopic technique. The calculated values of binding constants (K_b) are (9.22 ± 0.26) × 10⁵ L mol⁻¹ ( 1 -BSA), (7.19 ± 0.16) × 10⁵ L mol⁻¹ ( 1 -HSA), (5.05 ± 0.20) × 10⁵ L mol⁻¹ ( 2 -BSA) and (3.56 ± 0.25) × 10⁵ L mol⁻¹ ( 2 -HSA). The mechanism of serum albumins-complex interactions have been investigated by fluorescence lifetime measurement. Fluorescence spectroscopic studies indicate that both the complexes interact with calf thymas-DNA. Catecholase activity of the complexes has been studied in methanol using 3,5-di-tert-butylcatechol (3,5-DTBC) as substrate and the result show that both the complexes are active for catalytic oxidation of 3,5-DTBC to 3,5-di-tert-butylquinone (3,5-DTBQ) in presence of molecular oxygen. Calculated values of turnover numbers are 71.81 ± 1.04 h⁻¹ and 69.45 ± 0.74 h⁻¹ for 1 and 2 , respectively.     

Optimization of solar photocatalytic biodegradability of seawater using statistical modelling

The performance of zinc oxide (ZnO) as a photocatalyst was evaluated for the treatment of pollutants present in seawater. Batch experimental studies were carried out by varying the dosage of photocatalyst (1–4 ​g/L). The effect of reaction time, pH and the dosage of photocatalyst was evaluated with the percentage removal efficiencies of chemical oxygen demand (COD), biological oxygen demand (BOD), total organic carbon (TOC) and the biodegradability (BOD/COD) of the seawater. Response surface methodology-central composite design (RSM-CCD) and artificial neural network-Levenberg Marquardt (ANN-LM) statistical models were employed to optimize the photocatalytic biodegradability (BOD/COD). A quadratic polynomial statistical model was obtained to predict the percentage removal efficiencies of COD, TOC, BOD and biodegradability. For the experimental runs, the maximum percentage removal efficiencies for COD, TOC, BOD was found to be 62.3, 40.1, and 18.8%, respectively. Whereas, the maximum biodegradability was 0.036. As per RSM-CCD and ANN-LM statistical model method the maximum percentage removal efficiencies were found to be COD ​= ​58.14, 60.39%, TOC ​= ​33.74, 40.09%, BOD ​= ​18.47, 18.7% and Biodegradability ​= ​0.0315, 0.0360, respectively. The predicted values from statistical models were well correlated with experimental values. ANN modelling predicted better values for the responses with an average of R² ​= ​0.99697 than RSM modelling with average R² ​= ​0.8948.     

Synthesis and catalytic activity of binuclear cobalt(II) and nickel(II) complexes

Summary Binuclear Ni^II and Co^II complexes derived from 2,6-diformyl-4-methylphenol and various aromatic monoamines have been prepared and investigated. The Ni^II complexes have Ni₂LCl₃ composition while the Co^II complexes have Co₂L₂Cl₂ composition, where L represents the organic ligand. The complexes are active catalysts in the oxidation of 3,5-di-t-butylcatechol (3,5-DTBC) by dioxygen, but less so than their Cu analogues. This result is attributed to the absence of antiferromagnetic coupling between the metal centres.     

Copper(II)‐Mediated Transformation of a Tridentate Non‐Innocent Ligand into a Tetradentate Salen‐Type Innocent Ligand

A non‐innocent ligand, H₄L, was synthesized by introducing a ? CH₂NH₂ group at the ortho carbon atom to the aniline moiety of 2‐anilino‐4,6‐di‐tert‐butylphenol. The new ligand was characterized by IR and NMR spectroscopy and mass spectrometry techniques. Upon treatment with CuCl₂ ? 2 H₂O, this non‐innocent ligand provided a mononuclear four‐coordinate salen‐type Cu^II complex by complete modification of the ligand backbone. The complex was characterized by IR spectroscopy, mass spectrometry, X‐ray single‐crystal diffraction, electron paramagnetic resonance (EPR) spectroscopy, and UV/Vis/near‐IR spectroscopy techniques. X‐ray crystallographic analysis showed an asymmetric environment around the Cu^II center with a small (≈12°) twist between the two biting planes. Analysis of the X‐band EPR spectrum also supported the asymmetric environment and also indicated the presence of an unpaired electron on the d orbital. The UV/Vis/near‐IR spectrum showed strong absorption bands for metal‐to‐ligand charge transfer and ligand‐to‐metal charge transfer along with a Cu^II‐centered d–d transition. Mechanistic investigation of the formation of complex 1 indicated that modification of the ligand backbone proceeded through ligand‐centered amine to imine oxidation as well as through C? N bond‐breaking processes. During these processes, 3,5‐di‐tert‐butyl‐1,2‐benzoquinone and 2‐aminobenzylidene were produced. Ammonia, generated in situ through hydrolysis of the imine to the aldehyde, reacted with 3,5‐di‐tert‐butyl‐1,2‐benzoquinone to form the corresponding 3,5‐di‐tert‐butyl‐1,2‐iminobenzoquinone moiety, which upon two‐electron reduction in the reaction medium formed 3,5‐di‐tert‐butyl‐1,2‐aminophenol. This aminophenol underwent condensation with the H₂L5 ligand that was formed by self‐condensation of two molecules of 2‐aminobenzaldehyde and provided the modified ligand backbone.     

Synthesis of uranium complexes incorporating extended azo-imine ligands: Molecular and electronic structure

The new azo-imine ligands 2,4-di-tert-butyl-6-((2-((2-hydroxyphenyl)diazenyl) phenylimino)methyl)phenol, H₂L¹, 1a, and 2,4-di-tert-butyl-6-((2-((2-hydroxyphenyl) diazenyl)p-chlorophenylimino)phenol, H₂L², 1b, were prepared. Reaction of H₂L¹;1a, and H₂L²;1b, with uranyl nitrate hexahydrate afforded the mononuclear complexes of compositions [U(O)₂(L¹)(H₂O)]; 2a, and [U(O)₂(L²)(H₂O)]; 2b, complexes respectively. The newly synthesised ligands (1a and 1b) and the complexes (2a and 2b) were characterised unequivocally. The x-ray structure of 2a was determined. The tetradentate dianionic ligand (L¹)^2- coordinated the uranium ion equatorially with a water molecule in the same plane. Two axially coordinated oxo ligands completed the overall pentagonal bipyramid geometry around U(VI) ion. Structural pattern, electron transfer properties (oxidation near 1.32 ​V vs Ag/AgCl) and electronic transitions of [U(O)₂(L¹)(H₂O)]; 2a, and [U(O)₂(L²)(H₂O)]; 2b have been rationalized by DFT calculations.     

A new molecular building blocks: Synthesis,crystal structure,magnetic and spectroscopic properties of Cu(II) and Ni(II) macrocyclic complexes

New higly unsaturated macrocyclic building blocks [CuLSCN]·ClO₄ (1) (L = N-dl-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) and [NiL(SCN)₂] (2) (L = N-dl-5,12-dimethyl-7,14-diisopropyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) were synthesized and the crystal structures of both compounds were determined. Both complexes crystallizes in monoclinic, space group P2₁/n (1) and P2₁/c (2). Their magnetic properties were studied over the temperature range 1.8–300 K using a Quantum Design SQUID magnetometer (MPMSXL-5-type). The results indicate that both compounds behave as weakly interacting paramagnetic centers in the crystal lattice. The effects of hydrogen bond mediating the magnetic exchange interactions on the spin density have been evidenced by DFT calculations. The NIR–Vis–UV diffuse-reflectance electronic spectra confirm the square pyramidal and octahedral geometry around Cu²⁺ and Ni²⁺ metal ions.     

Synthesis and investigations of mixed-ligand lanthanide complexes with N,N′-dipyrrolidine-N′′-trichloracetylphosphortriamide,dimethyl-N-trichloracetylamidophosphate, 1,10-phenanthroline and 2,2′-bipyrimidine

Coordination compounds with general formula [Ln(L¹)₃phen], where Ln = Nd, Eu, Er, Yb, HL¹ = N,N′-dipyrrolidine-N′′-trichloracetylphosphortriamide, phen = 1,10-phenanthroline; [Ln(L¹)₃bpm], where Ln = La, Nd, Eu, Gd, Er, Y, bpm = 2,2′-bipyrimidine and [{Ln(L²)₃}₂(μ-bpm)], where Ln = La, Nd, Eu, Gd, Er, Y, HL² = dimethyl-N-trichloracetylamidophosphate have been synthesized and characterized by means of IR and UV–Vis spectroscopy. Crystal structures of [Nd(L¹)₃phen] (1), [Nd(L¹)₃bpm] (2) and [{Nd(L²)₃}₂(μ-bpm)] (3) have been determined. It was found, that in the deprotonated form the phosphoryl ligands (L¹)^? and (L²)^? are coordinated to the neodymium atoms in a bidentate manner via the oxygen atoms of the phosphoryl and the carbonyl groups with formation of six-membered metallocycles. In the case of compounds 1 and 2 the 1,10-phenanthroline (or 2,2′-bipyrimidine) molecules are coordinated to the metals in a bidentate manner via the nitrogen atoms. In contrast 2,2′-bipyrimidine acts in the bidentate-bridge mode forming binuclear complex 3. Variable-temperature magnetic susceptibility measurements of 3 and [{Gd(L²)₃}₂(μ-bpm)] (4) reveal a weak antiferromagnetic interaction between the two magnetic centres, whereas in the case of [{Eu(L²)₃}₂(μ-bpm)] (5) the presence of spin–orbit coupling leads to a deviation from the Curie and Curie–Weiss laws.     

Biomimetic oxidation of catechol employing complexes formed in situ with heterocyclic ligands and different copper(II) salts

In the present work, catecholase activity is presented. The complexes were prepared by condensation of the organic ligand pyrazolyl L ₁ –L ₄ and copper(II) ion in situ. The pyrazolyl compounds L ₁ –L ₄ used in this study are: L ₁ is (3,5-dimethyl-pyrazol-1-ylmethyl)-(4-methyl-pyridin-2-yl)-pyrazol-1-ylmethyl-amine; L ₂ is 1-{4-[(3,5-dimethyl-pyrazol-1-ylmethyl)-pyrazol-1-ylmethyl-amino]-phenyl}-ethanone; L ₃ is 1-{4-[(3,5-dimethyl-pyrazol-1-ylmethyl)-[1,2,4]triazol-1-ylmethyl-amino]-phenyl}-ethanone, and L ₄ is 2-[(3,5-dimethyl-pyrazol-1-ylmethyl)-[1,2,4]triazol-1-ylmethyl-amino]-6-methyl-pyrimidin-4-ol, and copper ions salts Cu(II) are (Cu(CH₃COO)₂, CuCl₂, Cu(NO₃)₂ and CuSO₄). In order to determine factors influencing the catecholase activity of these complexes, the effect of ligand nature, ligand concentration, nature of solvent and nature of counter anion has been studied. The best activity of catechol oxidation is given by the combination formed by one equivalent of ligand L ₂ and one equivalent of Cu(CH₃COO)₂ in methanol solvent which is equal to 9.09 µmol L^?1 min^?1. The Michaelis–Menten model is applied for the best combination, to obtain the kinetic parameters, and we proposed the mechanism for oxidation reaction of catecholase.     

Ferromagnetic exchange coupling in a new bis(μ-chloro)-bridged copper(II) Schiff base complex: Synthesis,structure, magnetic properties and catalytic oxidation of cycloalkanes

A new (μ-chloro)-bridged complex [Cu(HL)Cl]₂ · H₂O (1) with the Schiff base ligand H₂L, [2-((E)-(2-hydroxyethylimino)methyl)-4-bromophenol], has been synthesized and characterized by elemental analysis, IR, UV–Vis and EPR spectroscopic studies. X-ray diffraction studies show that 1 is a binuclear Cu^II complex with a pair of chlorine atoms bridging the copper atoms in a central Cu₂Cl₂ core. Each copper atom in 1 adopts a distorted square-pyramidal geometry with the imine nitrogen atom, alkoxy and phenoxy oxygen atoms from the Schiff base ligand and a bridging chlorine atom constructing the basal plane, while the apical position of the pyramid is occupied by the other bridging chlorine atom. Variable temperature susceptibility measurements show that complex 1 presents the highest ferromagnetic coupling [J = +43.2(5) cm⁻¹] reported till date in any doubly chloro-bridged Cu^II dimer, and a weak interdimer antiferromagnetic coupling [J′ = -0.276(8) cm⁻¹]. The complex also exhibits high catalytic activity towards the oxidation of hydrocarbons using H₂O₂ as terminal oxidant.