S. Vairam

3-Hydroxy-2-naphthoate Complexes of Transition Metals with Hydrazine - Preparation, Spectroscopic and Thermal Studies

Reaction of hydrazine and 3-hydroxy-2-naphthoic acid with some transition metal ions forms two types of complexes: (i) [M(N2H4){C10H6(3-O)(2-COO)(H2O) 2] where M=Ni, Co, Cd and Zn, at pH 9 and (ii) [M(N2H5)2{C10H6(3-O)(2-COO)} 2].xH2O where M=Ni & x =1; M=Co, Cd, Mn & x=3; and M=Zn, Cu & x =0 at pH 4. Analytical data confirms the compositions of the complexes. The acid shows dianionic nature in these complexes. The magnetic moments and electronic spectra suggest the geometry of the complexes. IR data indicates the nature of hydrazine and presence of water in the complexes. Simultaneous TG-DTA studies shows different thermal degradation patterns for the two types of complexes. The first type shows formation of no stable intermediates whereas the second type shows the respective metal hydroxy naphthoate intermediates. The final products in both the types are found to be metal oxides of nano size. XRD patterns show isomorphism among the complexes with similar molecular formulae.

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 possessing (AmgH)2[M(mal)2(H2O)2] [M = Co (1), Ni (2) or Zn (3); mal = malonate anion and AmgH = aminoguanidinium cation] stoichiometry and their solid solutions, (AmgH)2[Ni0.5Co0.5(mal)2(H2O)2] (4) and (AmgH)2[M1/3Co2/3(mal)2(H2O)2] [where M = Ni (5) or Zn(6)], were prepared and characterized by analytical, thermal and powder X-ray diffraction studies. The crystal and molecular structures of both cobalt and nickel compounds were isomorphic, crystallizing in the triclinic space group P. The complexes exhibit similar modes of endo-followed by exothermic decomposition to produce respective metal oxides below 550 °C. Metal cobaltites, MCo2O4 where M = Ni and Zn, were obtained from the above solid solutions as decomposition residues by heating at 600, 700 and 800 °C in a silica crucible for 3 h. Spinel oxides nanoparticles were characterized by infrared spectra, powder X-ray diffraction patterns, scanning electron microscope coupled with energy dispersive X-ray analysis and transmission electron microscope studies.

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.

Hydrazine Complexes of Lanthanides with 3-Acetoxy- and 4-Acetoxybenzoic Acids: Spectroscopic, Thermal, and XRD Studies

New bis-hydrazine lanthanide complexes with 3-acetoxybenzoic acid (3-abH) of formula, [Ln(3-ab)3(N2H4)2]·xH2O where Ln = La, Ce, Pr and Gd and 𝑥=0; Ln = Nd and Sm and 𝑥=1, and monohydrazine complexes of some trivalent lanthanides with 4-acetoxybenzoic acid (4-abH) of formula, [Ln(4-ab)3(N2H4)]·H2O where Ln = La, Ce, Pr, Nd, Sm and Gd have been prepared in ethanolic medium and characterized by spectroscopic techniques (IR and UV reflectance), microelemental analysis, thermoanalytical technique, powder XRD, SEM-EDS studies, and magnetic susceptibility measurements. The IR spectra of both series show bidental coordination of carboxylate ion with the metal by displaying, 𝜈C=O(asym) in the range of 1587–1602 cm−1 and the 𝜈C=O(sym) in the range of 1433–1410 cm−1, with a separation of around 200 cm−1. The ester C = O remains unaltered indicating the noninvolvement in coordination. All the complexes show 𝜈N−N absorption in the range of 929–962 cm−1 indicating the presence of hydrazine in a bridged bidentate fashion. The thermal data reveals that the hydrated compounds show endothermic dehydration followed by exothermic decomposition to leave their metal oxide as end products, and the anhydrous compounds undergo exothermic decomposition to form the respective metal oxide residues.

Synthesis, structural, optical and thermal analysis of nanostructured ZnO

Abstract Nanostructured zinc oxide (ZnO) has been synthesized via a one step solution based wet chemical method. Zinc acetate dihydrate (Zn (CH3COO)2 · 2H2O) was used as the precursor and its growth conditions were optimized for the formation of nanostructured ZnO. The powder pattern X-ray diffraction data of synthesized ZnO confirm particles of radius of about 20 nm with wurtzite hexagonal phase and preferential growth along (101) plane. Transmission electron microscopic results support the particle size value obtained through X-ray diffraction study. Clusters of nanostructured ZnO in agglomerated form are observed in scanning electron micrographs. The absorption bands observed at 509 cm−1 and 406 cm−1 in infrared spectra are assigned to ∊M-O of the synthesized compound. The absorption spectrum shows a narrow peak near the band edge in the exciton absorption region at about 371 nm and a blue shift is observed with respect to the bulk exciton absorption, 375 nm. Thermo-gravimetric analysis indicates weight loss corresponding to the formation of ZnO. The mechanism for the growth of nanostructured ZnO in solution has also been discussed.

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.