Tetra- and dinuclear nickel(II)-vanadium(IV/V) heterometal complexes of a phenol-based N2O2 ligand: synthesis, structures, and magnetic and redox properties

The tetra- and binuclear heterometallic complexes of nickel(II)-vanadium(IV/V) combinations involving a phenol-based primary ligand, viz., N,N'-dimethyl-N,N'-bis(2-hydroxy-3,5-dimethylbenzyl)ethylenediamine (H2L1), are reported in this work. Carboxylates and beta-diketonates have been used as ancillary ligands to obtain the tetranuclear complexes [Ni(II)(2)V(V)(2)(RCOO)(2)(L(1))(2)O(4)] (R = Ph, 1; R = Me(3)C, 2) and the binuclear types [(beta-diket)Ni(II)L(1)V(IV)O(beta-diket)] (3 and 4), respectively. X-ray crystallography shows that the tetranuclear complexes are constructed about an unprecedented heterometallic eight-membered Ni(2)V(2)O(4) core in which the (L(1))(2)- ligands are bound to the Ni center in a N(2)O(2) mode and simultaneously bridge a V atom via the phenoxide O atoms. The cis-N(2)O(4) coordination geometry for Ni is completed by an O atom derived from the bridging carboxylate ligand and an oxo O atom. The latter two atoms, along with a terminal oxide group, complete the O5 square-pyramidal coordination geometry for V. Each of the dinuclear compounds, [(acac)Ni(II)L(1)V(IV)O(acac)] (3) and [(dbm)Ni(II)L(1)V(IV)O(dbm)] (4) [Hdbm = dibenzoylmethane], also features a tetradentate (L(1))(2)- ligand, Ni in an octahedral cis-N(2)O(4) coordination geometry, and V in an O(5) square-pyramidal geometry. In 3 and 4, the bridges between the Ni and V atoms are provided by the (L(1))(2)- ligand. The Ni...V separations in the structures lie in the narrow range of 2.9222(4) A (3) to 2.9637(5) A (4). The paramagnetic Ni centers (S = 1) in 1 and 2 are widely separated (Ni...Ni separations are 5.423 and 5.403 A) by the double V(V)O(4) bridge that leads to weak antiferromagnetic interactions (J = -3.6 and -3.9 cm-1) and thus an ST = 0 ground state for these systems. In 3 and 4, the interactions between paramagnetic centers (Ni(II) and V(IV)) are also antiferromagnetic (J = -8.9 and -10.0 cm-1), leading to an S(T) = 1/2 ground state. Compound 4 undergoes two one-electron redox processes at E(1/2) = +0.66 and -1.34 V vs Ag/AgCl reference due to a V(IV/V) oxidation and a Ni(II)/I reduction, respectively, as indicated by cyclic and differential pulse voltammetry.     

Effect of various additives on the performance of a newly developed PVC based potentiometric sensor for anionic surfactants

A new poly(vinyl chloride) PVC membrane electrode to determine monomer concentrations of dodecylbenzenesulphonate ions (DBS⁻) based on a neutral ion-pair carrier complex of dodecyltrimethylammonium–dodecylbenzenesulphonate (DTA⁺–DBS⁻), is reported here. The electrode exhibits a slope of 51.25 mV per decade for DBS⁻ ions. The DBS⁻ ion selective electrode (ISE) can determine monomer units down to concentrations as low as 3.32 × 10⁻⁴ M. The effect of three kinds of additives, i.e. alcohols, glycols and triblock polymers on the performance of the surfactant selective electrode is studied systematically. The effect of foreign anions along with primary ions on the performance of ion-selective electrode is investigated in terms of potentiometric selectivity coefficients, which were determined using the fixed interference method (FIM) at 1.0 × 10⁻² M concentration of foreign anions. The sensor responds well to the surfactant ions in the presence of additives at lower concentration. The Gibbs free energy of micelle formation (ΔG_m) of sodium dodecylbenzenesulphonate (SDBS) in the presence of various additives is calculated and found to vary differently with respect to the increase in the amount of additives. The sensor worked in the acidic pH range with a short response time of 30 s. The lifetime of the sensor is more than three months. The sensor was further used to determine the amount of DBS⁻ in local detergents. This method of determining anionic surfactants was found to be quite accurate when compared with classical methods.     

Banana fiber-reinforced biodegradable soy protein composites

Banana fiber, a waste product of banana cultivation, has been used to prepare banana fiber reinforced soy protein composites. Alkali modified banana fibers were characterized in terms of density, denier and crystallinity index. Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were also performed on the fibers. Soy protein composites were prepared by incorporating different volume fractions of alkali-treated and untreated fibers into soy protein isolate (SPI) with different amounts of glycerol (25%–50%) as plasticizer. Composites thus prepared were characterized in terms of mechanical properties, SEM and water resistance. The results indicate that at 0.3 volume fraction, tensile strength and modulus of alkali treated fiber reinforced soy protein composites increased to 82% and 963%, respectively, compared to soy protein film without fibers. Water resistance of the composites increased significantly with the addition of glutaraldehyde which acts as cross-linking agent. Biodegradability of the composites has also been tested in the contaminated environment and the composites were found to be 100% biodegradable.     

Improved T(1)-weighted dynamic contrast-enhanced MRI to probe microvascularity and heterogeneity of human glioma

Dynamic contrast-enhanced (DCE) T(1)-weighted magnetic resonance imaging (MRI) is a powerful tool capable of providing quantitative assessment of contrast uptake and characterization of microvascular structure in human gliomas. The kinetics of the bolus injection doped with increasing concentrations of gadopentate dimeglumine (Gd-DTPA) depends on tissue as well as pulse sequence parameters. A simple method is described that overcomes the limitation of relative signal increase measurement and may lead to improved accuracy in quantification of perfusion indices of glioma. Based on an analysis of the contrast behavior of spoiled gradient-recalled echo sequence; a parameter K with arbitrary unit 5.0 is introduced, which provides a better approximation to the differential T(1) relaxation rate. DCE-MRI measurements of relative cerebral blood volume (rCBV) and cerebral blood flow (rCBF) were calculated in 25 patients with brain tumors (15=high-grade glioma, 10=low-grade glioma). The mean rCBV was 6.46 +/- 2.45 in high-grade glioma and 2.89 +/- 1.47 in the low-grade glioma. The rCBF was 3.94 +/- 1.47 in high-grade glioma while 2.25 +/- 0.87 in low-grade glioma. A significant difference in rCBF and rCBV was found between high- and low-grade gliomas. This simple and robust technique reveals the complexity of tumor vasculature and heterogeneity that may aid in therapeutic management especially in nonenhancing high-grade gliomas. We conclude that the precontrast medium steady-state residue parameter K may be useful in improved quantification of perfusion indices in human glioma using T(1)-weighted DCE-MRI.     

Dispersion of laser droplets using H+ ions and annealing effect on pulsed laser deposited nickel ferrite thin films

Nickel ferrite thin films were deposited by a pulsed laser deposition (PLD) technique on silicon substrate at room temperature in a vacuum of 5×10⁻⁵ mbar. The films were subjected to different annealing temperatures from 300–900°C and were also exposed to single shot energetic hydrogen ions using a Dense Plasma Focus (DPF) device. The changes induced in the films exposed at different distances from the top of the anode were investigated. The structural, morphological and magnetic properties of the annealed and exposed samples were investigated. X-ray diffraction (XRD) studies reveal the presence of a single phase of nickel ferrite after annealing. SEM micrographs indicate an increase in the grain size, both on annealing as well as on exposure to hydrogen ions. Annealing and hydrogen ion irradiation induced an enhancement in the magnetic moments. Laser droplets which are inherent in films deposited by laser ablation were found to be dispersed as a result of single shot hydrogen ion irradiation from the DPF.     

An efficient synthesis of some new 3-bipyridinyl substituted coumarins as potent antimicrobial agents

As a part of the ongoing studies in developing new antimicrobials,a series of structurally novel 3- bipyridinyl substituted coumarin derivatives 4a-f and 5a-f were synthesized by a single-step reaction protocol under Krohnke’s reaction conditions.¹H NMR,¹³C NMR,IR and mass spectral techniques were employed for the structural elucidation of the synthesized compounds.An evaluation of antimicrobial activity showed that almost all compounds exhibited better results than the referenced drugs.Among the synthesized derivatives 4f,5a and 5d were found to be the most potent analogs.Thus they could be promising lead for novel drugs.     

Extendability and von Neuman–Morgenstern stability of the core

This paper introduces a strengthening of the notion of a stable core and characterizes it in terms of Kikuta and Shapley’s extendability condition.     

Study on the compatibility of unbleached and bleached bamboo-fiber with LLDPE matrix

This article presents the comparative study on the compatibility of unbleached and bleached bamboo-fibers (UBF and BBF) with LLDPE matrix. Thermal characterization of composites was conducted by differential scanning calorimetry and thermogravimetric analysis. The results suggested that BBF are more compatible with matrix than the unbleached ones. The X-ray diffraction pattern shows no change in the intensity peak position of matrix in the presence of bamboo fibers. Morphological studies were done by scanning electron microscopy to get an idea of the compatibility of the fibers with the matrix. This study gives us the idea of using the bleached fiber for the preparation of the composites.