Co-ordination behaviour of hydrazine and isomers of acetoxy benzoic acids with transition metal ions

ABSTRACT. New hydrazine complexes of some divalent transition metal ions of formulae,                           [M{(2-ab)2(N2H4)}].3H2O, [M{(3-ab)2(N2H4)}].3H2O and [M{(4-ab)2(N2H4)2}].2H2O where M = Co, Ni, Zn and Cd; 2-abH = 2-acetoxy benzoic acid, 3-abH = 3-acetoxy benzoic acid and 4-abH = 4-acetoxy benzoic acid were prepared using their respective metal nitrates and hydrazine hydrate at pH 6 and 5, respectively, and characterized by elemental analysis, IR and UV-reflectance spectroscopic techniques, thermo analytical technique, powder XRD, SEM-EDX and magnetic susceptibility measurements. All the transition metal complexes were sparingly soluble in water. The IR spectra of complexes showed N-N absorptions of hydrazine in the range of 964-988 cm-1 substantiating the bidentate bridging coordination of hydrazine. They showed endothermic decomposition in the range of 67-100 °C, exothermic dehydrazination in the range, 210-281 °C and an oxidative decomposition between 350 and 490 °C to form their respective metal oxides. The electronic spectral and magnetic susceptibility data could substantiate the distorted octahedral geometry of nickel and cobalt complexes and the XRD pattern indicates the existence of isomorphism. Crystals of [Cd(H2O)3((C6H4(4-OH)(COO))2].H2O obtained as by-product, was also characterized using single crystal XRD, IR and thermal studies.                     KEY WORDS: Acetoxy benzoic acids, Hydrazine, Thermal analysis, Single crystal XRD   Bull. Chem. Soc. Ethiop. 2021, 35(2), 337-350.  DOI: https://dx.doi.org/10.4314/bcse.v35i2.9

Synthesis, characterization of cellulose acetate membrane and application for the treatment of oily wastewater

This study reports the synthesis of cellulose acetate (CA) membranes of different weight percentages of the polymer ranging from 5 to 17.5 wt% with 2.5% increment and their behaviour towards oil removal from water. The membrane showed decreased water content and porosity and also increased hydraulic resistance upto 3.38 kPa/(l m^-2 h^-1) as the concentration of polymer increases. The Atomic Force Microscopic studies reveal that the membrane shows decreased arithmetic mean roughness from 36.291 to 5.935 nm as the concentration of the polymer increases from 5% to 17.5%. Field Emission Scanning Electron Microscopy shows the surface morphology of the CA membrane. X-ray diffraction studies indicate that in the membrane having above 15% polymer concentration, the polymer chains orient to regularity showing higher crystallinity. The thermal studies indicate their stability upto 280°C, and exothermic decompositions from 338°C to 380°C implying the compactness of chains as polymer concentration increases. From Total Organic Carbon studies, the oil rejection was found to be maximum (96.4%) for the highest concentration of polymer in the membrane.

Elaeocarpus tectorius derived phosphorus-doped carbon as an electrode material for an asymmetric supercapacitor

Phosphorus-doped activated carbon from unexplored biomass was prepared, and it exhibits excellent electrochemical properties for green energy technology.

New barium, strontium and strontium-doped barium squarates: synthesis, crystal structures and DNA/BSA binding, antioxidant and in vitro cytotoxicity studies

A new set of differently hydrated barium and strontium squarates, namely poly[[triaqua(μ-1,2-dioxocyclobut-3-ene-1,2-diolato)barium] monohydrate], {[Ba(C₄O₄)(H₂O)₃]·H₂O}_n (1), poly[[diaqua(μ-1,2-dioxocyclobut-3-ene-1,2-diolato)strontium] monohydrate], {[Sr(C₄O₄)(H₂O)₂]·H₂O}_n (2), and poly[[triaqua(μ-1,2-dioxocyclobut-3-ene-1,2-diolato)barium/strontium(0.85/0.15)] monohydrate], {[Ba_0.85Sr_0.15(C₄O₄)(H₂O)₃]·H₂O}_n (3), is reported. The study of their crystal structures indicates that all the complexes crystallize in the triclinic space group P-1. Complexes 1 and 3 have a rare combination of squarate units coordinated through monodentate O atoms to two different metal atoms and through two bidentate O atoms to three different metal atoms. Furthermore, they have three coordinated water molecules to give a coordination number of nine. The squarate ligands in complex 2 exhibit two different coordination modes: (i) monodentate O atoms coordinated to four different Sr atoms and (ii) two monodentate O atoms coordinated to two different metal atoms with the other two O atoms bidentate to four different Sr atoms. All the compounds decompose to give the respective carbonates when heated to 800 °C, as evidenced by thermogravimetry/differential thermal analysis (TG-DTA), which are clusters of nanoparticles. Complexes 1 and 3 show additional endothermic peaks at 811 and 820 °C, respectively, indicating the phase transition of BaCO₃ from an orthorhombic (α-Pmcn) to a trigonal phase (β-R3m). All three complexes have significant DNA-binding constants, ranging from 2.45 × 10⁴ to 9.41 × 10⁴ M^-1 against EB-CT (ethidium bromide-calf thymus) DNA and protein binding constants ranging from 1.1 × 10⁵ to 8.6 × 10⁵ with bovine serum albumin. The in vitro cytotoxicity of the complexes is indicated by the IC₅₀ values, which range from 128.8 to 261.3 µg ml^-1. Complex 3 shows better BSA binding, antioxidant activity against the DPPH radical and cytotoxicity than complexes 1 and 2.

Synthesis of Co3O4/graphene nanocomposite using paraffin wax for adsorption of methyl violet in water

This study discusses the use of Co3O4 impregnated graphene (CoOIG) as an efficient adsorbent for the removal of methyl violet (MV) dye from wastewater. CoOIG nanocomposites have been prepared by pyrolyzing paraffin wax with cobalt acetate. The synthesised nanocomposite was characterised by X-ray diffraction, field emission scanning electron microscope, transmission electron microscope, Fourier transform infrared spectroscope, Raman spectroscopy, and Brunauer-Emmett-Teller isotherm studies. The above studies indicate that the composites have cobalt oxide nanoparticles of size 51-58 nm embedded in the graphene nanoparticles. The adsorption studies were conducted with various parameters, pH, temperature and initial dye concentration, adsorbent dosage and contact time by the batch method. The adsorption of MV dye by the adsorbent CoOIG was about 90% initially at 15 min and 98% dye removal at pH 5. The data were fitted in Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich and Sips isotherm models. Various thermodynamic parameters like Gibbs free energy, enthalpy, and entropy of the on-going adsorption process have also been calculated.

Isomorphic metal malonates with N-aminoguanidine: MCo2O4(M = Ni & Zn) nanoparticle synthesis via a (AmgH)2[M1/3Co2/3(mal)2(H2O)2] precursor solid solution

Divalent metal complexes of malonate with aminoguanidine and their solid solutions are prepared. The solid solutions are used as precursors for nanosized spinel oxides.

Magnetic activated carbon-Fe3O4 nanocomposites--synthesis and applications in the removal of acid yellow dye 17 from water

In this work, synthesis of activated carbon-Fe3O4 composites using activated carbon and iron benzoate/oxalate precursors by simple pyrolytic method and its utility for the removal of acid yellow dye from water are presented. Iron carboxylates held up into the pores of carbon dissociate at their decomposition temperatures form dispersed Fe3O4 nanoparticles in carbon matrix. The composites were characterized by FTIR, PXRD, SEM, TEM, EDX and magnetization measurements. The size of the nano iron oxides are in the range of 21-33 nm formed from iron benzoate precursor and 6-11 nm from iron oxalate precursor. The oxides are magnetic and their saturation magnetization in the range of 0.08-0.16 emu/g and Coercivity (H(c)) 474-600, being lower and higher than that of bare bulk Fe3O4 are due to the nano size of oxides. Composites find application in the removal of acid yellow dye 17 from the synthetic aqueous solution at pH 5. The adsorption data are found to fit well for Langmuir adsorption isotherm. Kinetics data of adsorption of dyes indicate that the adsorption follows pseudo-second order kinetic model.

Synthesis of magnetic activated carbon/α-Fe2O3 nanocomposite and its application in the removal of acid yellow 17 dye from water

The adsorption of acid yellow 17 dye on activated carbon/α-Fe2O3 nanocomposite prepared by simple pyrolytic method using iron(II) gluconate was investigated by batch technique. The composite was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). The size of iron oxide nanoparticles formed from iron(II) gluconate precursor is in the range 5-17nm. The saturation magnetization (Ms), remanence (Mr) and coercivity (Hc) of the magnetic carbon nanocomposite is 5.6emu/g, 1.14emu/g and 448Oe, respectively. The adsorption data are found to fit well with Langmuir and, fairly well with Freundlich and Tempkin isotherms at higher concentration of dye (40-100mg/L). Kinetics data indicate that the adsorption of dye follows pseudo-second order kinetics model.

The acid adducts hydrazinium 2-hydroxybenzoate-2-hydroxybenzoic acid (1/1) and hydrazinium 3-hydroxy-2-naphthoate-3-hydroxy-2-naphthoic acid (1/1)

The title molecular salts, N(2)H(5)(+)·C(7)H(5)O(3)(-)·C(7)H(6)O(3) and N(2)H(5)(+)·C(11)H(7)O(3)(-)·C(11)H(8)O(3), are acid adducts containing a hydrazinium cation, one molecule of a deprotonated acid and one molecule of a neutral acid. The two compounds contain essentially identical hydrogen-bond networks between the hydrazinium cation and the acid molecules, which define closely comparable two-dimensional layers in the structures. The planes of the aromatic rings within both structures are approximately parallel and the layers are stacked with comparable intermolecular interactions.