Showing papers in "Transition Metal Chemistry in 2011"

A Schiff base ligand N-(2-hydroxylacetophenone)-3-oxapentane-1,5-diamine and its nickel(II) complex: synthesis, crystal structure, antioxidation, and DNA-binding properties

Abstract: A new Schiff base ligand N-(2-hydroxylacetophenone)-3-oxapentane-1,5-diamine (HL) and its Ni complex, [Ni2(L)2(NO3)2], have been synthesized and characterized by physicochemical and spectroscopic methods. The X-ray crystal structure of [Ni2(L)2(NO3)2] shows it to be a dinuclear 2:2 complex, in which each Ni(II) atom is in a distorted octahedral geometry. The two Ni(II) atoms are dibridged by two phenoxo ligands, forming a Ni2O2 parallelogram-type moiety. The interactions between free HL and the complex with calf thymus DNA have been investigated, and the binding constant and linear Stern–Volmer quenching constant suggest that the two compounds bind to DNA via the intercalation mode. The binding affinity of the complex was higher than that of HL. Antioxidant assays in vitro showed that the Ni(II) complex possesses significant antioxidant activity.

Binuclear vanadium(V) complexes of bis(aryl)adipohydrazone: synthesis, spectroscopic studies, crystal structure and catalytic activity

Abstract: Three new binuclear vanadium(V) complexes of bis(aryl)adipohydrazones (H4L1 = bis((2-hydroxynaphthalen-1-yl)methylene)adipohydrazide, H4L2 = bis(5-bromo-2-hydroxybenzylidene)adipohydrazide, and H4L3 = bis(2-hydroxy-3-methoxybenzylidene)adipohydrazide) were synthesized by direct reaction of [VO(acac)2] with the hydrazone ligands. The ligands and complexes were characterized by FT–IR, UV–Vis, and NMR spectroscopic methods. The crystal structures of the complexes of L1 and L3 were determined by X-ray analyses. The solid-state structure of the complex of L1 features a 1D hydrogen-bonded chain from N⋯H–O hydrogen bonding. The catalytic activities of these complexes have been tested in the oxidation of various hydrocarbons using H2O2 as the terminal oxidant. Generally, good to excellent conversions have been obtained.

Synthesis, structure, and DNA-binding properties of manganese(II) and zinc(II) complexes with tris(N-methylbenzimidazol-2-ylmethyl)amine ligand

Abstract: Tris(N-methylbenzimidazol-2-ylmethyl)amine (Mentb) and its two complexes, [Mn(Mentb)(DMF)(H2O)](pic)2 1 and [Zn(Mentb)(pic)](pic) 2 (pic = picrate), have been synthesized and characterized by physico-chemical and spectroscopic methods. Single crystal X-ray diffraction revealed that the two complexes have different structures. In complex 1, the coordination sphere around Mn(II) is distorted octahedral, whereas in complex 2 the coordination sphere around Zn(II) is distorted trigonal bipyramidal. The DNA-binding properties of the free ligand and its two complexes have been investigated by electronic absorption, fluorescence, and viscosity measurements. The results suggest that the ligand and its two complexes bind to DNA via an intercalation binding mode, and their binding affinity for DNA follows the order 1 > 2 > ligand.

Characterization and activity of visible light–driven TiO2 photocatalysts co-doped with nitrogen and lanthanum

Abstract: Nitrogen and lanthanum co-doped titania photocatalysts were prepared by a modified sol–gel process with urea and lanthanum nitrate doping precursors and characterized by various techniques including XRD, FTIR, TEM, EDS, and UV–Vis DRS. The average crystallite size was ca. 12–15 nm as calculated from XRD patterns, and anatase was the dominant crystalline type in the as-prepared samples. The UV–Vis DRS of the samples revealed significant absorption within the range of 400–500 nm. The optimum composition of N(0.020)La(0.012)TiO2 exhibited the highest photocatalytic activity for degradation of methyl orange (MO) aqueous solution under simulated sunlight. The percent degradation of MO was ca. 97% for N(0.020)La(0.012)TiO2 under simulated sunlight irradiation for 9 h. The enhanced photocatalytic activity was ascribed to the synergistic effects of the nitrogen and lanthanum co-doping.

Synthesis of Ni/SiO2 nanoparticles for catalytic benzene hydrogenation

Abstract: Nickel nanoparticles supported on silica were prepared by hydrazine reduction in aqueous medium. The obtained solids were characterized by X-ray diffraction (XRD), Transmission Electronic Microscopy (TEM), Electron Diffraction (ED), hydrogen chemisorption, and Temperature Programmed Desorption of hydrogen (H2-TPD). The catalytic properties were evaluated for benzene hydrogenation in the temperature range 75–230 °C. XRD patterns reveal presence of the metallic nickel particles with fcc structure. Metal dispersion and hydrogen storage increase with decreasing metal particle size. The H2-TPD profiles exhibit two domains, one due to desorption of hydrogen from Ni metal and another due to spillover from metal to the support. The catalytic activity strongly depends on the metal loading. It increases with decreasing metal loading. This is attributed to metal surface area, which also increases with decreasing metal loading. Kinetic studies of benzene hydrogenation on the Ni catalysts showed that the benzene partial order is around −2. This significant negative value is ascribed to a strong adsorption of benzene on the catalyst surface.

A kinetic investigation into the rate of chloride substitution from chloro terpyridine platinum(II) and analogous complexes by a series of azole nucleophiles

Abstract: The substitution kinetics of the complexes [Pt(terpy)Cl]Cl·2H2O (PtL1), [Pt(tBu3terpy)Cl]ClO4 (PtL2), [Pt{4′-(2′′′-CH3-Ph)terpy}Cl]BF4 (PtL3), [Pt{4′-(2′′′-CF3-Ph)terpy}Cl]CF3SO3 (PtL4), [Pt{4′-(2′′′-CF3-Ph)-6-Ph-bipy}Cl] (PtL5) and [Pt{4′-(2′′′-CH3-Ph)-6-2′′-pyrazinyl-2,2′-bipy}Cl]CF3SO3 (PtL6) with the nucleophiles imidazole (Im), 1-methylimidazole (MIm), 1,2-dimethylimidazole (DIm), pyrazole (Pyz) and 1,2,4-triazole (Trz) were investigated in a methanolic solution of constant ionic strength. Substitution of the chloride ligand from the metal complexes by the nucleophiles was investigated as a function of nucleophile concentration and temperature under pseudo first-order conditions using UV/Visible and stopped-flow spectrophotometric techniques. The reactions follow the rate law $$ k_{\text{obs}} = k_{2} \left[ {\text{Nu}} \right] + k_{ - 2} $$ . The results indicate that changing the nature or distance of influence of the substituents on the terpy moiety affects the π-back-donation ability of the chelate. This in turn controls the electrophilicity of the metal centre and hence its reactivity. Electron-donating groups decrease the reactivity of the metal centre, while electron-withdrawing groups increase the reactivity. Placing a strong σ-donor cis to the leaving group greatly decreases the reactivity of the complex, while the addition of a good π-acceptor group significantly enhances the reactivity. The results indicate that the metal is activated differently by changing the surrounding atoms even though they are part of a conjugated system. It is also evident that substituents in the cis position activate the metal centre differently to those in the trans position. The kinetic results are supported by DFT calculations, which show that the metal centre is less electrophilic when a strong σ-donor is cis to the leaving group and more electrophilic when a good π-acceptor group is part of the ring moiety. The temperature dependence studies support an associative mode of activation. An X-ray crystal structure of Pyz bound to PtL3 was obtained and confirmed the results of the DFT calculations as to the preferred N-atom as a binding site.

Synthesis, characterization and antimicrobial activity of 3,5-di-tert-butylsalicylaldehyde-S-methylthiosemicarbazones and their Ni(II) complexes

Abstract: Ni(II) complexes were prepared by the reactions of 3,5-di-tert-butylsalicylaldehyde-S-methylisothiosemicarbazone (L) with salicylaldehyde or 2-hydroxy-1-naphthaldehyde in the presence of NiCl2·6H2O. The complexes and starting material L were characterized by physic-chemical analysis and spectroscopic techniques such as 1HNMR, 13CNMR, IR and UV–VIS. Antimicrobial activity studies of L and the two complexes standards strains of bacteria (Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), Bacillus cereus, Enterococcus faecalis, Streptococcus pneumoniae, Listeria monocytogenes, Escherichia coli, Salmonella typhi and Candida albicans) and 22 clinically isolated microorganisms, including multidrug resistant pathogenic microorganisms, were carried out. The free thiosemicarbazone L showed a significant inhibition of the growth all of Gram-positive bacteria tested.

Synthesis, structure, DNA-binding properties, and antioxidant activity of copper(II) and cobalt(II) complexes with bis( N -allylbenzimidazol-2-ylmethyl)benzylamine

Abstract: Bis(N-allylbenzimidazol-2-ylmethyl)benzylamine (babb) and two of its complexes, [Cu(babb)(pic)2]·H2O (1) and [Co(babb)2](pic)2 (2) (pic = picrate), have been synthesized and characterized by physico-chemical and spectroscopic methods. Single crystal X-ray diffraction revealed that the two complexes have similar distorted octahedral structures, but the degree of distortion and the coordinated atoms are different. The DNA-binding properties of the free ligand and its two complexes have been investigated by electronic absorption, fluorescence, and viscosity measurements. The results suggest that all three compounds bind to DNA via an intercalative binding mode, and their binding affinity for DNA follows the order 2 > 1 > ligand. Additionally, both complexes exhibited potential antioxidant properties in in vitro studies, and complex 1 was the more effective.

One-step synthesis of a Keggin-type manganese(II)-substituted phosphotungstate: structural and spectroscopic characterization and non-solvent liquid phase oxidation of styrene

Abstract: The Keggin-type Cs salt of a mono Mn(II)-substituted phosphotungstate (Cs5[PMnW11O39]) was synthesized from H3PW12O40, MnCl2 and CsCl. The complex was characterized in solution as well as in the solid state by spectroscopic, magnetic and electrochemical techniques. The complex crystallized in tetragonal phase. X-ray structural analysis shows two types of disorder in which the Mn and W atoms are distributed over the 12 positions, and the Mn atom could not be distinguished from the 11 W atoms distributed equally over the 12 addenda atoms in the Keggin structure. The catalytic activity of the complex was evaluated for non-aqueous oxidation of styrene using molecular oxygen. The complex gave >99.0% selectivity towards benzaldehyde and could be reused.

Spectroscopic, structure and DFT studies of palladium(II) complexes with pyridine-type ligands

Abstract: Five palladium(II) complexes with pyridine derivative ligands have been synthesized. The molecular structures of the complexes were determined by X-ray crystallography, and their spectroscopic properties were studied. Based on the crystal structures, computational investigations were carried out in order to determine the electronic structures of the complexes. The electronic spectra were calculated with the use of time-dependent DFT methods, and the electronic spectra of the transitions were correlated with the molecular orbitals of the complexes. The emission properties of the complexes have been examined.

Iron(III)–salen–H2O2 as a peroxidase model: electron transfer reactions with anilines

Abstract: Iron(III)–salen complexes catalyze the H2O2 oxidation of various ring-substituted anilines in MeCN have been studied, and [O=FeIV(salen)]+· is proposed as the active species. Study of the kinetics of the reaction by spectrophotometry shows the emergence of a new peak at 445 nm in the spectrum which corresponds to azobenzene. Further oxidation of azobenzene by H2O2 leads to the formation of azoxybenzene. ESI–MS studies also support the formation of these products. The rate constants for the oxidation of meta- and para-substituted anilines were determined from the rate of decay of oxidant as well as the rate of formation of azobenzene, and the reaction follows Michaelis–Menten kinetics. The rate data show a linear relationship with the Hammett σ constants and yield a ρ value of −1.1 to −2.4 for substituent variation in the anilines. A reaction mechanism involving electron transfer from aniline to [O=Fe(salen)]+· is proposed. The presence of axial ligands modulates the activity of the complex.

DNA-binding, antioxidant activity and solid-state fluorescence studies of copper(II), zinc(II) and nickel(II) complexes with a Schiff base derived from 2-oxo-quinoline-3-carbaldehyde

Abstract: A Schiff base derived from 2-oxo-quinoline-3-carbaldehyde-4-aminophenazone and its Cu(II), Zn(II) and Ni(II) complexes were synthesized. The molecular structures of the Zn(II) and Ni(II) complexes were determined by X-ray crystal diffraction. The DNA-binding modes of the compounds were investigated by spectroscopic methods, viscosity measurements and ethidium bromide-DNA displacement experiments. The experimental evidence indicated the compounds interact with calf thymus DNA through intercalation. Additionally, the compounds exhibited potential antioxidant properties in in vitro studies, and the Cu(II) complex was the most effective. The solid-state fluorescence properties of the Zn(II) complex were studied.

Coordination chemistry of [methyl-3-(4-benzyloxyphenyl)methylene]dithiocarbazate with divalent metal ions: crystal structures of the N,S Schiff base and of its bis-chelated nickel(II) complex

Abstract: The condensation of 4-benzyloxybenzaldehyde with S-methyldithiocarbazate (SMDTC) yielded the Schiff base methyl-3-[(4-benzyloxyphenyl)methylene] dithiocarbazate (HL) that, upon reaction with different metal ions, afforded bis-chelated complexes, ML2 [where M=Ni(II), Cu(II), Zn(II), Cd(II) or Pd(II)]. The ligand and all the metal complexes were characterized by physico-chemical and spectroscopic methods. The Schiff base and its bis-chelated Ni(II) complex were characterized also by single crystal X-ray analyses. The crystallographic results show that the Schiff base exists in thione tautomeric form with the dithiocarbazate fragment adopting an EE configuration with respect to the C=N bond of the group. In the NiL2 complex, the metal is chelated by two mononegatively charged Schiff bases coordinating via the β-nitrogen and thiolate sulfur anion, generated in situ during the complexation process, and adopts a distorted square planar geometry.

Synthesis, crystal structure, and DNA cleavage activity of a dinuclear nickel(II) complex with a macrocyclic ligand

Abstract: A new Ni(II) complex, namely [Ni2(OAc)L]·ClO4·H2O, was synthesized by [2 + 2] cyclo-condensation between 2,6-diformyl-4-methylphenol and N,N-bis(3-aminopropyl)-4-methoxybenzylamine (amba) in the presence of nickel(II) and characterized by spectroscopy, elemental analysis, and X-ray single crystal diffraction. The interactions of the complex with DNA have been measured by spectroscopy and viscosity measurements. Absorption spectroscopic investigation reveals intercalative binding of the Ni(II) complex with DNA, with a binding constant of 2.6 × 104 M−1. Fluorescence spectroscopy shows that the Ni(II) complex can displace ethidium bromide and bind to DNA, with a quenching constant of 7.57 × 103 M−1. The appearance of increased CD bands near 245 and 275 nm gives evidence for effective complex DNA binding. The agarose gel electrophoresis studies show that the complex displays effective DNA cleavage activity in the absence of any external agents.

Detection of single nucleotide polymorphisms by the specific interaction between transition metal ions and mismatched base pairs in duplex DNA

Abstract: Single nucleotide polymorphisms (SNPs) are base differences in the human genome. These differences are favorable markers for genetic factors including those associated with risks of complex diseases and individual responses to drugs. When two duplex DNAs with different types of SNPs are mixed and reannealed, the two novel heteroduplexes containing mismatched base pairs are formed in addition to the two initial perfectly matched homoduplexes. Heteroduplex analysis recognizing the newly formed mismatched base pairs is useful for SNP detection. Various strategies to detect the mismatched base pairs were devised due to the potential applications of SNPs. However, they were not always convenient and accurate. Here, we propose a novel strategy to detect the mismatched base pairs by the specific interaction between the Hg2+ ion and a T:T mismatched base pair and that between the Ag+ ion and a C:C mismatched base pair. UV melting indicated that the melting temperature of only the heteroduplexes with the T:T and C:C mismatched base pair specifically increased on adding the Hg2+ and Ag+ ion, respectively. Fluorescence resonance energy transfer analyses indicated that the intensity of fluorophore emission of only the fluorophore and quencher-labeled heteroduplexes with the T:T and C:C mismatched base pair specifically decreased on adding the Hg2+ and Ag+ ion, respectively. We propose that the addition of the metal ion could be a convenient and accurate strategy to detect the mismatched base pair in the heteroduplex. This novel strategy might make the heteroduplex analysis easy and eventually lead to better SNP detection.

Catalytic dehydrogenation of cyclohexene over MoO3/γ-Al2O3 catalysts

Abstract: A series of MoO3/γ-Al2O3 catalysts with different Mo surface densities (Mo atoms/nm2) has been prepared by incipient wetness impregnation method. Structural characteristics of the prepared catalysts were investigated by atomic absorption spectroscopy, X-ray diffraction, Fourier Transform Infrared spectroscopy, N2 adsorption at −196 °C, and temperature-programmed reduction (TPR). The catalytic activities of the prepared catalysts were tested by cyclohexene conversion between 200 and 400 °C. XRD results indicated that molybdenum oxide species were dispersed as a monolayer on the support up to 4.04 Mo atoms/nm2, and the formation of crystalline MoO3 was observed above this loading. FTIR and TPR results showed that molybdenum oxide species were present predominantly in tetrahedral form at lower loading, and polymeric octahedral forms were dominant at higher loading. Cyclohexene conversion reaction proceeded mainly through the simple dehydrogenation pathway in the studied temperature range 200–400 °C and was found to be highly dependent on MoO3 dispersion.

Assembly of four copper(II)–2,2′-biimidazole complex-supported Strandberg-type phosphomolybdates

Abstract: Four Strandberg-type phosphomolybdate-based Cu(II) complexes of 2,2′-biimidazole (C6H6N4, H2biim) and H2O molecules, namely [Cu(H2biim)2(H2O)][Cu(H2biim)2(HPO4)2(Mo5O15)]·2H2O (1), [{Cu(H2biim)(H2O)}2{μ-Cu(H2biim)(H2O)}(P2Mo5O23)]2·20H2O (2), [Cu(H2biim)2][{Cu(H2biim)(H2O)2}{Cu(H2biim)2}(HPO4)(PO4)(Mo5 O15)]2·20H2O (3), and [Cu(H2biim)2(H2O)][Cu(H2biim)2(HPO4)2(Mo5O15)]·6H2O (4) have been synthesized and characterized by physico-chemical and spectroscopic methods. Single-crystal X-ray diffraction analysis reveals that compound 1 consists of a mono-supporting heteropolyoxoanion [Cu(H2biim)2(H2P2Mo5O23)]2−and an isolated [Cu(H2biim)2(H2O)]2+ cation. Compound 2 is composed of two tetra-supporting heteropolyoxoanions linked via two Cu(II) complex fragments. In compound 3, there exist two symmetrical bi-supported polyoxoanion clusters and an isolated [Cu(H2biim)2]2+ fragment lying in the center of the clusters. Compound 4 is also constructed from a [Cu(H2biim)2(H2P2Mo5O23)]2− polyoxoanion and a [Cu(H2biim)2(H2O)]2+ cation, but it has a different space group and packing interactions compared with compound 1.

Radiosynthesis and characterization of the 99mTc-fleroxacin complex: a novel Escherichia coli infection imaging agent

Abstract: Radiocomplexation of fleroxacin (FXN) with technetium-99m and its characterization in terms of in vitro stability in saline and serum solutions, in vitro binding with live and heat-killed Escherichia coli, and biodistribution in male Wistar rats (MWR) artificially infected with live and heat-killed E. coli was studied. The 99mTc-FXN complex showed a radiochemical purity (RCP) yield of 98.10 ± 0.24% at 30 min using 125 μg of stannous fluoride, 74 MBq of sodium pertechnetate, and 2 mg of FXN. The complex was found to be more than 90% stable up to 4 h after constitution in normal saline. In serum, the emergence of 16.50% undesirable species was observed within 16 h of incubation at 37 °C. The 99mTc-FXN complex showed saturated in vitro binding with E. coli with a maximum value of 65.00% at 90 min. A fivefold increase in uptake of the complex was noted in the infected when compared with the inflamed and normal muscle of the MWR infected with live E. coli. The stable radiochemical profile in saline and serum, saturated in vitro binding with E. coli and increased uptake in the infected muscle, confirmed the potential of the 99mTc-FXN complex as an E. coli infection imaging agent.

Tuning the bridging modes of Cu-azido complexes with Schiff bases by varying the terminal groups

Abstract: Three azido-bridged copper(II) complexes, [Cu2(L1)2(μ1,1,3-N3)2] n ·2nH2O (1), [Cu4(L2)4(μ1,1-N3)2(μ1,1,3-N3)2] n (2), and [Cu2(L3)2(μ1,1-N3)2] (3), where L1, L2, and L3 are the deprotonated forms of 4-bromo-2-[(2-methylaminoethylimino)methyl]phenol (HL1), 4-bromo-2-[(2-ethylaminoethylimino)methyl]phenol (HL2), and 4-bromo-2-[(2-isopropylaminoethylimino)methyl]phenol (HL3), respectively, have been prepared and structurally characterized by single-crystal X-ray diffraction analysis and IR spectra. The slight differences in the terminal groups of the Schiff bases lead to different bridging modes of the azido groups.

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

Abstract: 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 1–3 when reacted with 4-nitrophenyl phosphate in 50:50 acetonitrile–water medium promote the cleavage of the O–P 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–vis spectrophotometry and the Michaelis–Menten 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.

Metathesis of butene to propene on WO3 supported on MTS-9 titanium-silica: effect of loading on selectivity of product and yield of propene

Abstract: An advanced heterogeneous catalyst for olefin disproportion was prepared by supporting WO3 on titanium-silica sieve (MTS-9). The nature of the surface tungsten oxide species present in these catalysts was determined as a function of tungsten oxide loading by X-ray diffraction (XRD), ultraviolet–visible diffuse reflectance spectra (UV–DRS) and ultraviolet–visible Raman (UV-Raman). The catalyst showed high activity for the metathesis of butene to propene. The active centers are not crystallites of WO3 but rather surface tungsten oxide species. The conversion of butene varies with the degree of catalyst loading.

Complexes of a diacetylmonoxime Schiff base of S-methyldithiocarbazate (H2damsm) with Fe(III), Ru(III)/Ru(II), and V(IV); catalytic activity and X-ray crystal structure of [Fe(Hdamsm)2]NO3·H2O

Abstract: The complexes [M(Hdamsm)2]X·H2O (M = Fe, X = NO3; M = Ru, X = Cl), [Ru(Hdamsm)(PPh3)2X′](X′ = Cl, Br), and [VO(Hdamsm)(acac)] (H2damsm = diacetylmonoxime Schiff base of S-methyldithiocarbazate, Hacac = acetylacetone) have been prepared and characterized by spectroscopic techniques. Their redox properties were investigated by cyclic voltammetry. The X-ray crystal structure of [Fe(Hdamsm)2]NO3.H2O has been determined and shows that the complex has a distorted octahedral geometry in which the Hdamsm behaves as a monoanionic NNS tridentate ligand coordinating via oxime nitrogen, hydrazinic imine nitrogen, and thiolate sulfur. The reactivity of these complexes toward oxidation of alcohols in the presence of t-BuOOH and H2O2 as co-oxidants is reported.

An iron(III)-containing ionic liquid: characterization, magnetic property and electrocatalysis

Abstract: The present work reports on the synthesis, characterization and performance of a new iron(III)-containing ionic liquid [(C4H9)2-bim][FeCl4] (Fe-IL, bim = benzimidazolium) as an electrocatalyst for nitrite and bromate reduction. The melting point of Fe-IL is 70 °C. Thermal behavior of the Fe-IL was studied by differential scanning calorimetry and thermalgravimetry. The value of magnetic moment and its temperature dependence were measured. A conductive carbon paste electrode (Fe-IL/CPE) comprised of Fe-IL and carbon powder was fabricated by the direct mixing method. The Fe-IL has double functions—a binder and an electrocatalyst. The electrochemical behavior and electrocatalysis of Fe-IL/CPE have been studied by cyclic voltammetry. The Fe-IL/CPE shows excellent electrocatalytic activities toward nitrite and bromate reduction. The detection limit and the sensitivity are 0.01 μM and 100.58 μA μM−1 for nitrite, and 0.01 μM and 83.11 μA μM−1 for bromate detection, respectively. This work demonstrates that the Fe-IL may become a new kind of functional material in constructing chemicals and biosensors.

Aminophosphine ligands: synthesis, coordination chemistry, and activity of their palladium(II) complexes in Heck and Suzuki cross-coupling reactions

Abstract: The reaction of 4-aminodiphenylamine or 2-aminofluorene with two equivalents of PPh2Cl in the presence of Et3N gives new bis(diphenylphosphino)amines N,N-bis(diphenylphosphino)-4-aminodiphenylamine 1 and N,N-bis(diphenylphosphino)-2-aminofluorene 2 in good yields. Oxidation of 1 or 2 with hydrogen peroxide, elemental sulfur or gray selenium affords the corresponding chalcogen derivatives. The palladium and platinum complexes of these P–N–P donor ligands were prepared by the reaction of the bis(phosphino)amines with MCl2(cod) (M = Pd or Pt, cod = cycloocta-1,5-diene). All the new compounds have been characterized by analytical and spectroscopic methods, including 1H-31P NMR, 1H-13C HETCOR, or 1H-1H COSY correlation experiments. The Pd(II) complexes were investigated as catalysts in the Suzuki and Heck reactions; both showed good catalytic activity affording high yields of the desired products.

Catalytic activity of a zirconium(IV) Schiff base complex in facile and highly efficient synthesis of indole derivatives

Abstract: Eight Schiff base compounds were prepared by condensation of 1-amino-2-propanol with different benzaldehydes in water. One of the Schiff bases, (z)-N-bezylidene-2-hydroxypropane-1-amine (HL1), was used as a bidentate ligand for preparation of a zirconium complex (Zr(L1)2Cl2). The complex has been used as a catalyst for efficient synthesis of wide variety of indole derivatives in EtOH under mild conditions. The turnover number and reusability of the catalyst indicate that it has high efficiency and is fairly stable under the reaction conditions.

Synthesis, structure, CMC values, thermodynamics of micellization, steady-state photolysis and biological activities of hexadecylamine cobalt(III) dimethyl glyoximato complexes

Abstract: Metallosurfactant complexes of the type trans- [Co(DH)2(HA)X], where DH = Dimethyl glyoxime, HA = Hexadecyl amine and X = Cl−, Br−, I−, N3 −, NO2 − or SCN−, were synthesized and characterized by physico-chemical and spectroscopic methods. In addition, the single crystal X-ray structure of the ionic complex trans-[Co(DH)2(HA)2][Co(DH)2(I)2)] is presented. The critical micelle concentration values of the complexes in ethanol were obtained by measuring the absorption at 290 nm. Specific conductivity data (at 303–313 K) served for the evaluation of the thermodynamics of micellization $$ \left( {\Updelta G^{0}_{{{\text{m}}}}, \Updelta H^{0}_{{{\text{m}}}}, \Updelta S^{0}_{\text{m}} } \right) $$ . Steady-state photolysis, cyclic voltammetry and biological activities of the complexes were studied. The compounds were tested for antimicrobial activity.

5-Nitro-1,10-phenanthroline bis(N,N-dimethylformamide-Κ′O)-bis(perchlorato) copper(II): synthesis, structural characterization, and DNA-binding study

Abstract: The hexa-coordinated copper(II) complex [Cu(L)(DMF)2(ClO4)2], where L = 5-nitro-1,10-phenanthroline, was synthesized and characterized. The X-ray crystal structure shows that the copper is coordinated by the two N-atoms of the 1,10-phenanthroline ligand plus four O-atoms, two from DMF ligands and two from the perchlorate anions. Thermal analysis showed that the complex was stable up to 285 °C. The interaction of the complex with calf thymus DNA was investigated using absorption and emission spectroscopic studies, and the binding constant (K b) and linear Stern–Volmer quenching constant (K sv) have been determined. Electrochemical characterization of the complex in acetonitrile showed a quasi-reversible one-electron exchange voltammogram for the Cu2+/Cu+ redox couple at ca. E 1/2 = −1.00 V (versus SCE) with ΔE = 200 mV and i pc/i pa ≈ 1.

Fabrication of highly active Sn/W mixed transition-metal oxides as solid acid catalysts

Abstract: Catalytically active Sn/W mixed transition-metal oxides were prepared by calcination of the corresponding Sn/W hydroxide precursors at different temperatures. The obtained mixed oxides were characterized by physicochemical and spectroscopic methods. With variation of the molar ratios of Sn/W, the prepared Sn/W mixed oxide catalysts had different reaction activities. Thus, the Sn/W-2-800 oxide acted as an effective heterogeneous catalyst for the Baeyer–Villiger oxidation of ketones and the Friedel–Crafts reaction. Many ketones, as well as benzyl alcohol and acetic anhydride, were transformed into the corresponding products with high conversion and selectivity. The catalysts can be easily separated from the reaction mixtures and can be reused for at least five cycles without significant loss of activity.

A ternary copper(II) complex for supramolecular assembly with double helices: synthesis, crystal structure, DNA-binding and DNA-cleavage properties

Abstract: A ternary Cu(II) complex, [Cu(naph-ser)(bipy)]·0.125CH2Cl2 (naph-ser = a Schiff base derived from 2-hydroxy-1-naphthaldehyde and l-serine, bipy = 2, 2′-bipyridine), has been synthesized and structurally characterized. In the crystal structure, a supramolecular assembly with left-handed double helices is formed by O–H···O hydrogen bonding interactions. The DNA-binding properties and DNA-cleavage activity of the Cu(II) complex have been investigated by spectroscopic methods and agarose gel electrophoresis. The results indicate that the Cu(II) complex can bind to CT-DNA via an intercalative mode and shows efficient cleavage activity in the absence and presence of reducer.

Synthesis, characterization, and electrochemical properties of diiron azadithiolate complexes related to the active site of [FeFe]-hydrogenases

Abstract: Treatment of [(μ-SCH2)2NPh]Fe2(CO)6 (A) with PPh3 or PPh2H in the presence of the decarbonylating agent Me3NO·2H2O afforded complexes [(μ-SCH2)2NPh]Fe2(CO)5(PPh3) (1) and [(μ-SCH2)2NPh]Fe2(CO)5(PPh2H) (2) in 87% and 74% yields, respectively. Complexes 1 and 2 were characterized by elemental analysis and various spectroscopic techniques. The molecular structures of 1 and 2 were further determined by X-ray crystallography. In both cases, the monophosphine ligand resides in an axial position of the square-pyramidal Fe atom and trans to the benzene ring of the azadithiolate ligand, in order to minimize steric repulsion. On the basis of electrochemical studies, all these complexes were found to catalyze proton reduction to H2 in the presence of acetic acid.