Palladium(II) complexes of Schiff bases derived from 5-amino-2,4-(1H, 3H)pyrimidinedione (5-aminouracil) and 1,2-dihydro-1,5-dimethyl-2-phenyl-4-amino-3H-pyrazol-3-one

Summary New palladium(II) complexes of Schiff bases, obtained from 5-aminouracil, (AUH), and acetylacetone (AUAcAcH₂), benzaldehyde (AUBALH), furan-2-aldehyde (AUFALH), 2-hydroxynaphthaldehyde (AUNALH₂), pyridine-2-aldehyde (AUPyALH) or salicylaldehyde (AUSALH₂) and from 1,2-dihydro-1,5-dimethyl-2-phenyl-4-amino-3H-pyrazol-3-one (AAPy) and acetylacetone (AAPyAcAcH), 2-hydroxyacetophenone (AAPyAPH), furan-2-aldehyde (AAPyFAL), pytidine-2-aldehyde (AAPyPyAL), or salicylaldehyde (AAPySALH), have been prepared. The complexes, with formulae PdL₂Cl₂ (L=AUBALH, AUFALH or AUSALH₂); PdLCl₂ (L=AUAcAcH₂, AUNALH₂, AUPyALH, AAPyFAL or AAPyPyAL) and PdLCl (L=AAPyAcAc or AAPySAL) were characterized by elemental analysis, i.r. and electronic spectral studies, thermogravimetric analyses and magnetic and conductance measurements. The x-ray powder diffraction pattern of one of the complexes was also examined. The complexes were screened for their possible antitumour activityin vitro.     

Enhanced metal extractive behavior using dual mechanism bifunctional polymer: an effective metal chelatogen

A new class of chelating polymers using Amberlite XAD-16 (AXAD-16) modified with (N-(3,4-dihydroxy)benzyl)-4-amino,3-hydroxynapthalene-1-sulphonic acid has been developed based on dual mechanism bifunctional polymers, for the extraction of transition and post-transition metal ions. The optimum pH conditions for the quantitative sorption of metal ions were studied. The developed method showed superior extraction qualities with high metal loading capacities of 71, 85, 182, 130 and 46 mg g⁻¹ for Ni(II), Cd(II), Pb(II), Cu(II) and Co(II), respectively. The rate of metal ion uptake i.e. kinetics studies performed under optimum levels showed a time duration of <5 min except for Co(II) which required 20 min, for complete metal ion saturation. Desorption of metal ions were effective with 15 ml of 2 M HCl/HNO₃ prior to detection using flame atomic absorption spectrophotometer. The chelating polymer was highly ion-selective in nature even in the presence of large concentrations of alkali and alkaline earth metal ions, with a high preconcentrating ability for the metal ions of interest. The developed chelating matrix was tested on its utility with synthetic and real samples like river/sea/tap/well water samples and also with multivitamin/mineral tablets, showed R.S.D. values of <2.5% reflecting on the accuracy and reproducibility of data using the newly developed resin matrix.     

Preparation,spectral characterization,electrochemistry, EXAFS,antibacterial and catalytic activity of new ruthenium (III) complexes containing ONS donor ligands with triphenylphosphine/arsine

New hexa‐coordinated ruthenium (III) complexes of the type [RuX(EPh₃)₂(L)] (X = Cl or Br; L = dibasic tridentate Schiff base ligand; E = P or As) have been synthesized by the reactions of [RuCl₃(PPh₃)₃], [RuCl₃(AsPh₃)₃] or [RuBr₃(AsPh₃)₃] with the appropriate Schiff base ligands derived by the condensation of salicylaldehyde and 2‐hydroxy‐1‐naphthaldehyde with N(4) substituted thiosemicarbazones. All the new complexes were characterized using various physico‐chemical methods such as elemental analyses, infrared, electron paramagnetic resonance (EPR) spectroscopy, magnetic moment and cyclic voltammetry. Based on the extended X‐ray absorption fine structure (EXAFS) analysis, an octahedral structure has been confirmed for the complexes. The new complexes have been subjected to the catalytic activity and antibacterial studies. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis,spectral characterization,electrochemistry and catalytic activities of Cu(II) complexes of bifunctional tridentate Schiff bases containing O?N?O donors

Paramagnetic copper(II) complexes of the type [Cu(PPh₃)(L)] (where L = bifunctional tridentate Schiff bases) were synthesized from the reaction of anthranillic acid with salicylaldehyde (H₂L¹), 2‐hydroxy‐1‐naphthaldehyde (H₂L²), o‐hydroxyacetophenone (H₂L³) and o‐vanillin (H₂L⁴) with monomeric metal precursor [CuCl₂(PPh₃)₂]. The obtained complexes were characterized by elemental analysis, magnetic susceptility and spectroscopic methods (FT‐IR, UV–vis and EPR and cyclic voltammetry). EPR and redox potential studies have been carried out to elucidate the electronic structure, nature of metal–ligand bonding and electrochemical features. EPR spectra exhibit a four line pattern with nitrogen super‐hyperfine couplings originating from imine nitrogen atom. These planar complexes possess a significant amount of tetrahedral distortion leading to a pseudo‐square planar geometry, as is evidenced from EPR properties. Cyclic voltammograms of all the complexes display quasireversible oxidations, Cu(III)? Cu(II), in the range 0.31–0.45 V and reduction peaks, Cu(II)? Cu(I),in the range ?0.29 to ?0.36 V, involving a large geometrical change and irreversible. The observed redox potentials vary with respect to the size of the chelate ring of the Schiff base ligands. Further, the catalytic activity of all the complexes has been found to be high towards the oxidation of alcohols into aldehydes and ketones in the presence of N‐methylmorpholine‐N‐oxide as co‐oxidant. The formation of high valent Cu^IV?O oxo species as a catalytic intermediate is proposed for the catalytic process. Copyright © 2008 John Wiley & Sons, Ltd.     

Direct observation of orbital ordering in La0.5Sr1.5MnO4 using soft x-ray diffraction

We report the first direct resonant soft x-ray scattering observations of orbital ordering. We have studied the low temperature phase of La0.5Sr1.5MnO4, a compound that displays charge and orbital ordering. Previous claims of orbital ordering in such materials have relied on observations at the manganese K edge. These claims have been questioned in several theoretical studies. Instead we have employed resonant soft x-ray scattering at the manganese L(III) and L(II) edges which probes the orbital ordering directly. Energy scans at constant wave vector are compared to theoretical predictions and suggest that at all temperatures there are two separate contributions to the scattering: direct orbital ordering and strong cooperative Jahn-Teller distortions of the Mn3+ ions.     

Three-dimensional spin fluctuations in Na0.75CoO2

We report polarized- and unpolarized-neutron scattering measurements of magnetic excitations in single-crystal Na0.75CoO2. The data confirm ferromagnetic correlations within the cobalt layers and reveal antiferromagnetic correlations perpendicular to the layers, consistent with an A-type antiferromagnetic ordering. The magnetic modes propagating perpendicular to the layers are sharp, and reach a maximum energy of approximately 12 meV. From a minimal spin-wave model, containing only nearest-neighbor Heisenberg exchange interactions, we estimate the interlayer and intralayer exchange constants to be 12.2+/-0.5 meV and -6+/-2 meV, respectively. We conclude that the magnetic fluctuations in Na0.75CoO2 are highly three dimensional.     

Charge stripe glasses in La<Subscript>2-x</Subscript>Sr<Subscript>x</Subscript>NiO<Subscript>4</Subscript> for 0.20 < x < 0.25

We present high resolution X-ray measurements characterising the charge stripe order state in the La_2-xSr_xNiO₄ system with x = 0.20, 0.225 and 0.25. We find that in the x = 0.20, 0.225 and 0.25 systems the charge stripe order exists in a charge stripe glass characterised by weak, poorly correlated incommensurate charge stripes in contrast to the strong well correlated charge stripes in the commensurate x = 1/3 system. No stabilisation of the charge order was observed at the next possible commensurate value of ε= 0.25. A comparison with high energy X-ray measurements suggested that the charge order may exist in a charge stripe glass in the bulk in the doping region x = 0.20 - 0.33. Finally at low temperature there was an initial increase in the intensity and correlation not observed with neutron measurements and it appears to be an effect that X-rays are sensitive to but neutrons are not.     

The interpretation of isoclinics in photo-orthotropic-elasticity

Significant progress has been made in the interpretation of isochromatic fringes in photo-orthotropic-elasticity. However, the isoclinic fringes have not yet been satisfactorily interpreted. While it has been recognized that the isoclinics do not give the principal-stress directions in the composite model, there has been speculation that the isoclinics may give the principal-strain directions. An experimental study of the isoclinic fringes in orthotropic models was undertaken. The model material employed consisted of a transparent, unidirectionally reinforced, E-glass-polyester composite. First, the optical isoclinic parameters were measured in uniaxial stress fields for compression specimens as a function of the fiber-orientation angle. It was observed that, while the optical isoclinic parameter was different from the composite principal-stress angle, it was also different from the composite principal-strain angle. The optical isoclinic parameter was predicted very well by the Mohr circle of birefringence postulated by Sampson. In the second set of experiments, the optical isoclinic parameter was measured in biaxial stress fields by testing a circular disk in diametral compression. The actual state of strain and stress at the center of the disk was measured by means of a rectangular strain-gage rosette. Again it was observed that the optical isoclinic parameter was predicted very well by Sampson's relation. Thus, the isoclinic fringes in orthotropic models can be satisfactorily interpreted and Sampson's scheme can be utilized to obtain the individual principal stresses in orthotropic models.     

A pseudo trinuclear nickel–sodium complex containing tris(8-methyl-2-oxo-quinolidineamino ethylamine): Synthesis,spectral characterization,X-ray crystallography and in vitro biological evaluations

A new mixed nickel–sodium complex has been synthesized from Ni(ClO₄)₂ and tris(8-methyl 2-oxo-quinolidine amino ethylamine) with a 1:1 molar ratio in methanol and has been characterized by various analytical, spectroscopy and X-ray diffraction studies which confirmed an octahedral geometry around the nickel ion. Further, structural optimization of the complex was performed using DFT calculations. The ligand and complex were evaluated for their binding affinity with CT-DNA and an intercalative type of binding interaction was proposed from the absorption and fluorescence titration experiments. Albumin binding interaction of the ligand and complex was determined by absorption, fluorescence and synchronous spectral techniques at room temperature, suggesting the static quenching mechanism of BSA with the compounds. Antioxidant studies revealed the radical scavenging potential of Ni(II) complex. The anticancer activity of the ligand and complex was probed via in vitro cytotoxicity against human breast (MCF7) and lung (A549) cancer cell lines by MTT assay. Further, cytological changes observed in acridine orange/ethidium bromide and DAPI staining methods validated the cytotoxic potential of the complex.