X-ray Structure of Bis（salicylidene）-p-diaminobenzene

IntroductionThe interactions between molecules involvingaromatic ring systems are of interest because oftheir effects on the structures and aggregation ofimportant biomolecules,on template efficiency in avariety of organic reactions,and on the solid statestructures of a variety oforganic molecules[1] .Con-sistent are the analysis results of more than 2 0 0phenylalanine- phenylalanine interactions in thecrystal structures of various proteins,which leadsto the following conclusions.( 1 ) Direct …     

On the way to chiral epoxidations with methyltrioxorhenium(VII) derived catalysts

Methyltrioxorhenium(VII) (MTO) is successfully applied as chiral epoxidation catalysts in the presence of H₂O₂ as oxidizing agent and excess chiral Lewis base ligands derived from pyrazole. Moderate enantiomeric excesses up to ca. 30% can be reached at low reaction temperatures (−30 °C), the conversions however, being quite low (<25%). The reason for this may be the fluctionality of the N-base ligand. Glycolate complexes of MTO, applied under the same conditions reach somewhat higher enantiomeric excesses (up to ca. 40%), however, again associated with low conversions (<30%). In this case the sensitivity of the catalyst to water induced ligand removal as well as to ligand exchange with other diols is the most likely reason. Nevertheless, the enantiomeric excesses reported here are among the best observed for MTO derived catalytic systems reported to date and more active and selective systems seem feasible.     

Palladium(II) Complexes of N-(2-Thienylmethylidene)aniline Derivatives

Coordination reactions of N-(2-thienylmethylidene)aniline derivatives, L, with PdCl₂ or [PdCl₄]^2? in ethanol yield stable complexes of the type trans-(L)₂PdCl₂ with the azomethine nitrogen atoms as σ donors. These are not readily convertible to othor-palladated complexes. An X-ray crystallographic study of the complex (L₂)₂PdCl₂ reveals a centrosymmetric geometry. The structure is in the triclinic space group $ {\rm P}\bar 1 $ with a = 8.633(2) Å, b = 12.759(3) Å, c = 8.398(2) Å, α = 96.65(5)°, β = 111.47(5)*, γ= 101.28(6)°, and Z = 1. The final R factor is 0.043 (Rw = 0.044) for 2396 observed reflections. There is no real bonding between a thiophene sulfur atom and a central palladium ion. However, a long distance interaction between S and Pd does exist.     

Mononuclear and dinuclear chiral vanadium(V) complexes with tridentate Schiff bases derived from R(−)-1,2-diaminopropane: Synthesis,structure, characterization and catalytic properties

A series of vanadium(V) complexes with unsymmetrical tridentate Schiff base ligands, obtained by the single condensation of R(−)-1,2-diaminopropane with salicylaldehyde and its derivatives, 2-hydroxy-1-naphthaldehyde, 2-hydroxyacetophenone, 1-hydroxy-2-acetonaphthone and 2-hydroxybenzophenone, were prepared. The complexes were characterized by elemental analysis and by their IR, CD, UV–Vis, 1D (¹H, ⁵¹V) and 2D (COSY, NOESY, gHSQC) NMR spectra. Crystal structures of the mononuclear complex {R(−)-2-amino-1-N-[(2′-oxido-κO-4′,6′-dimethoxyphenyl)methylene]aminopropane-κ²N}dioxidovanadium(V), VO₂(C₁₂H₁₇N₂O₃), 4, and of the dinuclear complex, di-μ-oxido-bis({R(−)-2-[1-(2-aminopropylimino)ethyl]-4-methylphenolato-κ³N,N′,O}oxidovanadium(V)), V₂O₄(C₁₁H₁₅N₂O)₂, 5, have been obtained by X-ray diffraction studies. The structure of 4 was revealed to be a distorted trigonal–bipyramidal coordination geometry, rarely encountered in VO₂(tridentate Schiff base) complexes. Complexes 2 and 3 have the ability to catalyze the oxidation of prochiral sulfide substrates PhSR (R = Me, Bz) utilizing hydrogen peroxide or cumene hydroperoxide (CHPO) as the oxidant.     

Thermal behavior of vanadyl complexes with Schiff bases derived from trans-N,N′-bis(salicylidene)-1,2-cyclohexadiamine (t-Salcn)

Several Schiff bases coordinated to vanadyl, VO(Schiff base), were synthesized, characterized and studied by thermogravimetry in order to evaluate their thermal stability and thermal decomposition pathways. The number of steps and, in particular, the starting temperature of decomposition of these complexes depend on the equatorial ligand. The intermediates of the thermal decomposition processes were characterized by their IR spectra.     

Synthesis,crystal structure,and antibacterial activity of mononuclear nickel(II) and cobalt(III) Schiff-base complexes

Four new mononuclear complexes, [Ni(L¹)(NCS)₂] (1), [Ni(L²)(NCS)₂] (2), [Co(L¹)(N₃)₂]ClO₄ (3), and [Co(L²)(N₃)₂]ClO₄ (4), where L¹ and L² are N,N′-bis[(pyridin-2-yl)methylidene]butane-1,4-diamine and N,N′-bis[(pyridin-2-yl)benzylidene]butane-1,4-diamine, respectively, have been prepared. The syntheses have been achieved by reaction of the respective metal perchlorate with the tetradentate Schiff bases, L¹ and L², in presence of thiocyanate (for 1 and 2) or azide (for 3 and 4). The complexes have been characterized by microanalytical, spectroscopic, single crystal X-ray diffraction and other physicochemical studies. Structural studies reveal that 1–4 are distorted octahedral geometries. The antibacterial activity of all the complexes and their constituent Schiff bases have been tested against Gram-positive and Gram-negative bacteria.     

Copper(II) azide complexes with mono-anionic tridentate Schiff-base ligands: monomer versus dimer

Three new copper(II) complexes [CuL¹N₃]₂ (1), [CuL²N₃] (2) and [CuL³N₃] (3) with three very similar tridentate Schiff base ligands [HL¹?=?6-diethylamino-3-methyl-1-phenyl-4-azahex-3-en-1-one, HL²?=?6-amino-3-methyl-1-phenyl-4-azahex-3-en-1-one and HL³?=?6-amino-3-methyl-1-phenyl-4-azasept-3-en-1-one] have been synthesized and structurally characterized by X-ray crystallography. In complex 1 half of the molecules are basal-apical, end-on azido bridged dimers and the remaining half are square-planar monomers whereas all the molecules in complexes 2 and 3 are monomers with square-planar geometry around Cu(II). A competition between the coordinate bond and H-bond seems to be responsible for the difference in structure of the complexes.     

(N‐Salicylidene)aniline Derived Schiff Base Complexes of Methyltrioxorhenium(VII): Ligand Influence and Catalytic Performance

It′s a fine line : Methyltrioxorhenium(VII) (MTO) readily forms 1:1 adducts with several N‐(salicylidene)aniline derived Schiff bases. Steric and electronic effects of the ligands play a major role when it comes to stability and catalytic activity. Good donors on the Schiff base ligands, in general, lead to shorter Re? O(Schiff base) bridges and lower catalytic activity, while it is the opposite for acceptor ligands on the Schiff bases.

     

Copper(II) complexes with singly condensed tridentate Schiff-base ligands incorporating 1-benzoylacetone

Two copper(II) complexes [CuL¹Cl]_n (1) and [CuL²Cl] (2) with singly condensed tridentate Schiff-base ligands [HL¹ = 6-amino-3-methyl-1-phenyl-4-azahex-3-en-1-one and HL² = 6-diethylamino-3-methyl-1-phenyl-4-azahex-3-en-1-one] have been synthesized and structurally characterized by X-ray crystallography. Complex 1 is a single-chloro-bridged one-dimensional polymer, whereas 2 is a monomeric square-planar complex. The H-bonding interactions of the amine hydrogen and the non-bonding interactions of phenyl groups in the Schiff base play important roles for the structural variations.     

Synthesis,characterization, and insulin-enhancing studies of unsymmetrical tetradentate Schiff-base complexes of oxovanadium(IV)

A series of unsymmetrical tetradentate Schiff bases were synthesized by interaction of 2-hydroxy-1-naphthaldehyde, phenylenediamine and salicylaldehyde, or substituted salicylaldehyde in an ethanolic medium. The oxovanadium(IV) complexes and the ligands were synthesized and characterized by elemental analyses, ¹H NMR, infrared, electron paramagnetic resonance, electronic spectra, cyclic voltammetry, and room temperature magnetic susceptibility measurements. The elemental analyses for both the ligands and the metal complexes confirmed purity of the compounds as formulated. Electron paramagnetic resonance spectra of the complexes were measured as powder and in toluene/dichloromethane (9 : 1, v/v) solution at room and liquid N₂ temperatures. The g values, g _o = 1.971, g _⊥ = 1.978, and g = 1.950, are the same for all the complexes examined. The vanadium nuclear hyperfine splitting, A _o = 101–99, A _⊥ = 65–64, A _∥ = 179–177, vary slightly with substituents on the salicylaldehyde. Infrared spectra reveal strong V=O stretching bands in the range 970–988 cm^?1, typical of monomeric five-coordinate complexes. The room temperature magnetic moments of 1.6–1.8 BM for the complexes confirmed that the complexes are V(IV) complexes, with d¹ configuration. Only one quasi-reversible wave is observed for each compound and they all showed redox couples with peak-to-peak separation values (ΔE _p) ranging from 78 to 83 mV, indicating a single step one electron transfer process. Insulin-mimetic tests on C2C12 muscle cells using Biovision glucose assay showed that all the complexes significantly stimulated cell glucose utilization with negligible cytotoxicity at 0.05 µg µL^?1.     

Cobalt(II) and nickel(II) chelates of some 5-pyrazolone-based,Schiff-base ligands

The cobalt(II) and nickel(II) chelates of Schiff bases, derived by condensing 4-butyryl-3-methyl-1-phenyl-2-pyrazolin-5-one (BMPP) with o-, m-, p-phenylenediamine, benzidine, and ethylenediamine have been synthesized and characterized by elemental analyses, thermogravimetric analyses (TGA), conductance data, magnetic measurements, IR, ¹H NMR, ¹³C NMR, mass, and electronic spectroscopies. Each of the Schiff bases was an ONNO donor to metal forming chelates formulated as [M(L)(H₂O)₂] _n with M = Ni(II) and Co(II) and L is the di-anion of the Schiff base. The monomeric (n = 1) and dimeric (n = 2) species of these metal chelates, based on available evidence, are suggested.     

Synthesis,characterisation and X-ray structure of an azido adduct of a tridentate (NNO) Schiff base nickel(II) complex

The tridentate Schiff base 1-(N-salicylideneimino)-2-(N,N-diethyl-aminoethane (HL), derived from the condensation of salicylaldehyde with N,N-diethylethylenediamine, reacted with nickel(II) nitrate and azide to give a mononuclear complex of formula [Ni(L)(N₃)], where HL?=?Et₂N(CH₂)₂NCHC₆H₄(OH). The complex was characterized by spectroscopic and X-ray crystallographic methods. Coordination around nickel(II) is square planar. The molecular and supramolecular structure of the complex is discussed.     

Crystal structure and luminescence of antimony(III) bromide with aniline

The atomic structure of antimony(III) bromide crystals with anilinium was determined by X-ray diffraction analysis of (C₆H₅NH₃)₂SbBr₅ (a = 19.704(3) Å, b = 7.914(1) Å, c = 25.556(4) Å; space group Pbca, Z = 8, ρ_calc = 2.365 g/cm³). The crystal structure consists of infinite chains of [SbBr₅]^2? complex anions formed by sharing six vertices and the anilinium (C₆H₅NH₃)⁺ cations, through which the chains are linked in layers by N-H...Br hydrogen bonds. The geometrical aspects that determine the luminescent spectral properties of the complex are discussed.     

Synthesis,characterization, antibacterial,and thermal studies of unsymmetrical Schiff-base complexes of cobalt(II)

Cobalt(II) complexes of a new series of unsymmetrical Schiff bases have been synthesized and characterized by their elemental analyses, melting points, magnetic susceptibility, thermogravimetric analysis, differential scanning calorimetry, infrared (IR), and electronic spectral measurements. The purity of the ligands and the metal complexes are confirmed by microanalysis, while the unsymmetrical nature of the ligands was further corroborated by ¹H-NMR. Comparison of the IR spectra of the Schiff bases and their metal complexes confirm that the Schiff bases are tetradentate and coordinated via N₂O₂ chromophore. The magnetic moments and electronic spectral data support square-planar geometry for the cobalt(II) complexes. The complexes were thermally stable to 372.3°C and their thermal decomposition was generally via the partial loss of the organic moiety. The Schiff bases and their complexes were screened for in vitro antibacterial activities against 10 human pathogenic bacteria and their minimum inhibitory concentrations were determined. Both the free ligands and cobalt(II) complexes exhibit antibacterial activities against some strains of the microorganisms, which in a number of cases were comparable with, or higher than, that of chloramphenicol.     

Spectroscopic,thermal and antimicrobial properties of the copper(II) complex of Schiff base derived from 2‐(salicylidene) aminopyridine

Schiff bases and their complex combinations with metallic ions represent a class of compounds with antimicrobial activity. A ligand was prepared by condensation of the salicylaldehyde with 2‐aminopyridine obtaining 2‐(salicylidene) aminopyridine (SB) with a high capacity for complexing Cu(II) ions. The new compound has been characterized by physical constants (melting point, solubility, stability) and the chemical structure was confirmed by elemental, spectral (IR, UV–visible, ¹H NMR and ¹³C‐NMR) and thermal analyses. The elemental analysis gives a coordination ratio of 1:2 metal:Schiff base. Lethal dose 50 (DL₅₀) values of new Schiff base and their complex with metallic ions were established. The antimicrobial activity of this complex was tested in comparison with the activity of the corresponding Schiff base on strains of Staphylococcus aureus, Bacillus cereus, Bacillus subtilis, Escherichia coli, Candida albicans, and Klebsiella. These were compared with the activity of the reference drugs (chloramphenicol, tetracycline, ofloxacin and nystatin) on the above‐mentioned strains. It has been established that all compounds tested were very active against both Gram‐positive and Gram‐negative bacteria. Copyright © 2012 John Wiley & Sons, Ltd.     

Gelatin/poly(aniline) composite films: Synthesis and characterization

In this work, glyoxal (Glox) - crosslinked gelatin (Gel) films have been loaded with aniline molecules, followed by their in-situ oxidative polymerization to yield Gel/poly(Ani) composite films. The films, so prepared, have been characterized by FTIR, XRD, TGA and AFM analysis. The water absorption of these films has been studied in the physiological fluid of pH 7.4 at 37°C.The dynamic water uptake data has been interpreted by various kinetic models such as power function model and Schott kinetic model. The various diffusion coefficients have also been evaluated.     

非对称N-(亚水杨基)二亚乙基三胺铜(Ⅱ)配合物的合成、结构分析和催化活性评价(英文)

A new copper(Ⅱ) complex of a non‐symmetric Schiff base, [CuII(saldien)(H2O)]+(1), has been synthesized and characterized by elemental analysis and several other spectroscopic methods (Hsaldien = N‐(salicylidene)diethylenetriamine). The crystal structure of 1 has also been determined by X‐ray crystallography. The geometry of the complex cation in 1 was found to be distorted square pyramidal with the mononegative Schiff base coordinating to the copper in a tetradentate mode via the O,N,N’, and N’’‐donor atoms. The remaining coordination site was occupied by the O atom of a H2O molecule in the axial position. The catalytic potential of 1 was tested in the oxidation reactions of cyclooctene and cyclohexene with aqueous 30% H2O2/NaHCO3 in acetonitrile. These reactions proceeded smoothly to give the corresponding epoxides with selectivity levels greater than 99%. This catalytic system also showed high levels of activity and selectivity towards the oxidation of cyclohexane (i.e., cyclohexanol 37% and cyclohexanone 54%) in comparison with most of the other Cu‐based systems reported in the literature.     

Syntheses and crystal structures of two Schiff-base copper(II) complexes with antibacterial activities

Two structurally similar trinuclear complexes, [Cu(Cu(μ-Cl)₂L1)₂] (1) and [Cu(Cu(μ-Cl)₂L2)₂] (2) (HL1 = 4-chloro-2-[(2-morpholin-4-ylethylimino)methyl]phenol, HL2 = 1-[(2-piperidin-1ylethylimino)methyl]naphthalen-2-ol), have been synthesized and structurally characterized. Both complexes are bridged trinuclear compounds. The central Cu in each complex is in an octahedral environment with two phenolate and four bridging chlorides. The symmetry-related terminal Cu in each complex is square pyramidal with one phenolate oxygen, one imine nitrogen and one amine nitrogen of the Schiff-base ligand, one Cl^? in the basal plane, and one bridging Cl^? in the apical position. The complexes and Schiff bases were tested in vitro for their antibacterial activities.     

Ascorbate amperometric determination using conducting copolymers from aniline and N-(3-propane sulfonic acid)aniline

The sequential electrochemical polymerization of aniline and N-(3-propane sulfonic acid)aniline (PSA) is proposed to construct a sensor able to detect ascorbate at physiological conditions. Compared to poly(aniline) modified electrode, a device with improved conducting and electrochemical properties at neutral pH is obtained. The electrochemical copolymerization of the same starting materials is also carried out. For a PSA:aniline ratio of 10:90, a polymer with a similar electrochemical behavior to the one grown in the sequential mode is observed.The detection of ascorbate was tested for both configurations at pH 7.2, the modified electrode is able to determine ascorbate at 0 mV versus Ag/AgCl; an optimized sensor constructed by sequential polymerization can easily detect ascorbate concentrations with a detection limit of 2.2 μM. Uric acid and dopamine does not interfere in the ascorbate determination.