• N Y Vasanthacharya

Articles written in Journal of Chemical Sciences

• Magnetic susceptibility studies of Mn1-xMxO (M = Zn, Mg, Fe)

Magnetic susceptibility studies of Mn1-xMxO (M = Zn, x≤0.1; M = Mg, x≤0.12;M = Fe, x≤0.4) in the range 77 to 300 K are reported. The methods of preparation of Mn1-xMxO systems preclude the presence of trivalent ions. The M1-xFexO system shows anomalous behaviour aroundx = 0.2–0.3. The results are discussed in terms of competition between the nearest neighbour and the next-near-neighbour interactions, dilution effects and cooperative effects of FeO6 octahedra.

• Role of carboxylate ion and metal oxidation state on the morphology and magnetic properties of nanostructured metal carboxylates and their decomposition products

Sub-micron rods and spheres of cobalt succinate sesquihydrate and iron succinate trihydrate/pentahydrate respectively have been synthesized by the reverse micellar route. These precursors are an excellent source for the synthesis of metal and metal oxide nanoparticles. Cubes of (edge length ∼ 150 nm) Fe3O4 and elongated particles of Fe2O3 (∼ diameter of 200 nm) were obtained. The role of oxidation state of the metal ion in controlling the morphology of the nanostructured dicarboxylates has been investigated. Rods with shorter length were obtained when longer chain dicarboxylate was used as ligand. Heating in nitrogen atmosphere also provided pure Co and 𝛼-Fe nanoparticles. The Fe nanoparticles show nearly 100% superparamagnetism. Temperature-dependent magnetic studies show a Morin-like transition for Fe2O3 nanoparticles at 223 K and the Verwey transition at 115 K for Fe3O4 nanoparticles. Co3O4 nanoparticles showed antiferromagnetic ordering at 20 K.

• Supramolecular network formed through O-H$\cdots$O and $\pi-\pi$ stacking interactions: Hydrothermal syntheses and crystal structures of M(H2O)6](optp)2 (M = Mg, Ni, Zn, and optp = 1-oxopyridinium-2-thiopropionate)

A novel class of complexes of the type [M(H2O)6](optp)2 (where M = Mg, Ni, Zn, and optp = 1-oxopyridinium-2-thiopropionate) were prepared hydrothermally from metal acetates and 1-oxopyridinium-2-thiopropionic acid (Hoptp), and structurally characterized by X-ray diffraction. Complexes [Mg(H2O)6](optp)2 (1), [Ni(H2O)6](optp)2 (2) and [Zn(H2O)6](optp)2 (3) have isomorphic structures, consisting of one [M(H2O)6]2+ cation and two anions of Hoptp, which are linked through hydrogen bonding to form extended networks. In each case, the metal cation sits on a crystallographic centre of inversion and binds to six water molecules. The organic anions form a one-dimensional chain with the hexaaquametal(II) moieties via hydrogen bonds.

• Manganese-mediated ferromagnetism in La2Fe$_{1-x}$Mn$_{2x}$Cr$_{1-x}$O6 perovskite oxides

We have investigated the structure and magnetic properties of the perovskite oxides of the formula La2Fe$_{1-x}$Mn$_{2x}$Cr$_{1-x}$O6 ($0 &lt; x &lt; 1.0$). For $0 &lt; x ≤ 0.5$, the members adopt the orthorhombic (Pbnm) structure, where the transition metal atoms are disordered at the 4b sites and the MO6 (M = Fe, Mn, Cr) octahedra become increasingly distorted with increasing 𝑥. For $0.65 ≤ x &lt; 1.0$, the members adopt the rhombohedral (R-3c) structure that is similar to LaMnO$_{3+\delta}$ ($\delta ≥ 0.1$) where the MO6 octahedra are undistorted. While the magnetic properties of the latter series are largely similar to the parent LaMnO$_{3+\delta}$ arising from the double-exchange (DE) between mixed valent MnIII/MnIV, the magnetic properties of the orthorhombic members show a distinct (albeit weak) ferromagnetism ($T_C \sim 200$ K) that seems to arise from a MnIII-mediated superexchange (SE) between FeIII/CrIII in the disordered perovskite structure containing FeIII, MnIII and CrIII.

• # Journal of Chemical Sciences

Volume 135, 2023
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• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019