• Kandalam V Ramanujachary

Articles written in Journal of Chemical Sciences

• Reverse micellar synthesis and properties of nanocrystalline GMR materials (LaMnO3, La0.67Sr0.33MnO3 and La0.67Ca0.33MnO3): Ramifications of size considerations

Nanoparticles of complex manganites (viz. LaMnO3, La0.67Sr0.33MnO3 and La0.67Ca{0.33}MnO3) have been synthesized using the reverse micellar route. These manganites are prepared at 800‡C and the monophasic nature of all the oxides has been established by powder X-ray diffraction studies. TEM studies show an average grain size of 68, 80 and 50 nm for LaMnO3, La0.67Sr0.33MnO3 and La0.67Ca{0.33}MnO3respectively. Ferromagnetic ordering is observed at around 250 K for LaMnO3, 350 K for La0.67Sr0.33MnO3 and 200 K for La0.67Ca{0.33}MnO3. These Curie temperatures correspond well with those reported for bulk materials with similar composition.

• 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.

• Design of non-molecular coordination solids from aqueous solution: [CuIILnX(H2O)], where X=SO4, Cl or H2O and L=pyrazole, imidazole or glutamic acid and 𝑛 = 1 or 4

We have successfully crystallized four new non-molecular coordination solids utilizing the synthons-Cu-OSO3- and -Cu-Cl- in the presence of four organic ligands:[{Cu($pz$)4SO4}{Cu(pz)4SO4 (H2O)}]. H2O2, [Cu(imi)4SO4]3, [Cu(imi)4(NO3)2]4 and [Cu(glu)Cl(H2O)]5. Use of glutamic acid resulted in two chiral coordination polymers 5 and [Cu(glu)(H2O)]. H2O 6 depending on the copper source. The paper provides chemical insights to the supramolecular aggregation of a crystal driven by the various competing intermolecular forces.

• # Journal of Chemical Sciences

Volume 134, 2022
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Posted on July 25, 2019