- Mechanosynthesis of multiferroic hybrid organic-inorganic [NH4][M(HCOO)3] M = Co2+,Mn2+,Zn2+,Ni2+, Cu2+ formate-based frameworks
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The family of compounds with formula [NH4][M(HCOO)3], with M a divalent D-metal, is characterized by porous frameworks hosting NH4+ cations exhibiting at low temperature a spontaneous ferroelectric polarization. The presence of magnetically active divalent metal determines the occurrence of antiferromagnetic ordering below 30 K opening the avenue for a rational formulation of a new class of multiferroic materials. We demonstrate that this intriguing class of compounds can be synthetized with a mechanochemical approach. This novel route of synthesis was applied to the series [NH4][M(HCOO)3] with M= Cu2+, Co2+, Mn2+, Zn2+ and Ni2+ using as reactants ammonium formate and the corresponding di-hydrated metal formates. The milling duration of the process correlates with the thermal stability of the di-hydrated metal formates indicating that the first step of the mechanosynthesis process is represented by the removal of water molecules. The characterizations of the final products indicate the presence of single phase [NH4][M(HCOO)3] compounds with an excellent degree of crystallinity.
- Bersani, Danilo,Calestani, Davide,Cugini, Francesco,Gemmi, Mauro,Griesi, Andrea,Orlandi, Fabio,Righi, Lara,Solzi, Massimo,Vit, Valentina
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supporting information
(2021/12/23)
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- Metal(II) Formates (M = Fe, Co, Ni, and Cu) Stabilized by Tetramethylethylenediamine (tmeda): Convenient Molecular Precursors for the Synthesis of Supported Nanoparticles
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γ-Alumina supported 3d transition-metal nanoparticles are commonly used catalysts for several industrial reactions, such as Fischer-Tropsch, reforming, methanation, and hydrogenation reactions. However, the activity of such catalyst is often limited by the low metal dispersion and a high content of irreducible metal, inherent to the conventional preparation methods in aqueous phase. In this context, we have recently shown that [{Ni(μ2-OCHO)(OCHO)(tmeda)}2(μ2-OH2)] (tmeda=tetramethylethylenediamine) is a suitable molecular precursor for the formation of 1–2 nm large nanoparticles onto alumina. Here, we explore the synthesis of the corresponding Fe, Co, and Cu molecular precursors, namely [{Fe(μ2-OCHO)(OCHO)(tmeda)}4], [{Co(μ2-OCHO)(OCHO)(tmeda)}2(μ2-OH2)], [Cu(κ2-OCHO)2(tmeda)], which are, like the Ni precursor, soluble in a range of solvents, rendering them convenient metal precursors for the preparation of supported metallic nanoparticles on γ-alumina. Using a specific adsorption of the molecular precursor on γ-alumina in a suitable organic solvent, treatment under H2 provides small and narrowly distributed Fe (2.5±0.9 nm), Co (3.0±1.2 nm), Ni (1.7±0.5 nm), and Cu (2.1±1.5 nm) nanoparticles. XAS shows that the proportion of MAl2O4 (M = Co, Ni, Cu) is small, thus illustrating the advantage of using these tailor-made molecular precursors.
- Margossian, Tigran,Larmier, Kim,Allouche, Florian,Chan, Ka Wing,Copéret, Christophe
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- Magnetic behavior of the metal organic framework [(CH3)2NH2]Co(HCOO)3
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In this study we examine the phase transitions in single crystals of [(CH3)2NH2]Co(HCOO)3, using magnetization and specific heat measurements as a function of temperature and magnetic field. Magnetisation measurements indicate a transition at 15 K that is associated with an antiferromagnetic ordering. Isothermal magnetization versus magnetic field curves demonstrate the presence of a single-ion magnet phase, coexisting with antiferromagnetism. A peak in specific heat is seen at 15 K, corresponding to a magnetic transition and the enthalpy of the transition evaluated from the area under the specific heat peak which decreases with the application of a magnetic field of up to 8 T. This is suggestive of long range antiferromagnetic magnetic order, giving way to single-ion magnetic behavior under an external magnetic field. At high temperatures, the specific heat measurements show a peak at ～155 K that is insensitive to the applied magnetic field. Raman scattering studies confirm the presence of a structural transition. The magnetisation in this temperature range, while exhibiting a paramagnetic behavior, shows a distinct jump and the paramagnetic susceptibility changes across the structural transition.
- Vinod,Deepak,Sharma, Shilpam,Sornadurai,Satya,Ravindran,Sundar,Bharathi
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p. 37818 - 37822
(2015/05/13)
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- Synthesis and photocatalytic properties of low-dimensional cobalt-doped zinc oxide with different crystal shapes
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The glycoxide complexes Zn1-x Co x (HCOO)(HOCH 2CH2O)1/2 and Zn1-x Co x (OCH2CH2O) (0 ≥ x ≥ 0.3) have been synthesized by heating ethylene glycol solutions of zinc formate Zn(HCOO)2 ? 2H2O or its mixtures with cobalt formate Co(HCOO)2 ? 2H2O. The crystals of these complexes have the shape of filaments (needles, bars) and distorted octahedra, respectively. A new method in which these complexes are used as the precursor is suggested for the synthesis of low-dimensional wurtzite-like Zn1-x Co x O. The shape of the precursor crystals is fully inherited by Zn1-x Co x O resulting from their heat treatment. The Zn1-x Co x O solid solutions show high photocatalytic activity in hydroquinone oxidation in aqueous solution under UV or blue light irradiation, and their activity increases as their cobalt content is increased.
- Krasil'nikov,Gyrdasova,Buldakova, L. Yu.,Yanchenko, M. Yu.
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p. 145 - 151
(2011/05/04)
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- Ordered olivine-type lithium-cobalt and lithium-nickel phosphates prepared by a new precursor method
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Single phases of olivine-type LiCoPO4 and LiNiPO4 were synthesized by thermal treatment of homogeneous lithiummetal-phosphate- formate precursors obtained by freeze drying of aqueous solutions of the corresponding metal formates and LiH2PO4. The structure, thermal behavior, and morphology of the precursors were studied by IR spectroscopy, DTA, and SEM. Cobalt and nickel phosphate-formate precursors have a composition LiMHx(PO4)(HCOO)x-yH 2O, where the formate and phosphate groups are mainly deprotonated. For the Co precursor the formate and phosphates ions are randomly coordinated to both Co and Li cations, for the Ni precursor there is a preferential coordination of the formate and phosphate ions around the Ni2+ and Li+ ion, respectively. Thermal treatment of the precursors yields single phases of olivine-type LiCoPO4 at 450 °C and LiNiPO4 at 700 °C. Structural analysis evidences that both LiCoPO4 and LiNiPO4 have an ordered olivine-type structure without any Li to M disorder between the metal positions and lithiurm deficiency. The effect of the freeze-dried solution concentration and annealing temperature on the structure, crystallite size, and morphology of LiCoPO4 and LiNiPO4 has been discussed. The morphology of the cobalt and nickel phospho-olivines comprises isometric particles with mean sizes of 190 and 380 nm, respectively.
- Koleva, Violeta,Zhecheva, Ekaterina,Stoyanova, Radostina
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p. 4091 - 4099
(2011/01/08)
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- Double formates Ba2M(HCOO)6(H2O) 4 (M = Co, Ni, Cu, Zn): Crystal structures and hydrogen bonding systems
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The crystal structures of four members in the isomorphous series, Ba 2M(HCOO)6(H2O)4 (M=Co, Ni, Cu, Zn) are presented and thoroughly discussed. Discrepancies with a previous structural report on the Cu isolog [Z. Kristallogr. 110 (1958) 231] were cleared out through a re-refinement of the original data, the outcome of which definitely confirmed the present results. The strengths of the hydrogen bonds in the title compounds as deduced from the infrared wavenumbers of the uncoupled OD stretches of matrix-isolated HDO molecules are discussed in terms of the O w?O hydrogen bond lengths, the different hydrogen bond acceptor capabilities of the formate oxygen atoms and the weak Ba-OH2 interactions. The proton acceptor strength of the oxygen atoms is evaluated within the framework of the Brown's bond-valence theory. The intramolecular OH bond lengths are derived from the novel νOD vs. rOH correlation curve [J. Mol. Struct. 404 (1997) 63].
- Baggio,Stoilova,Polla,Leyva,Garland
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p. 173 - 180
(2007/10/03)
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- Perovskite-like metal formates with weak ferromagnetism and as precursors to amorphous materials
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Three isomorphous compounds M(CHOO)3[NH2(CH 3)2] (M = Mn(1·Mn), Co(2·Co), Ni(3·Ni)) have been synthesized in solvothermal conditions. Single-crystal X-ray diffraction shows that they are all crystallized in the trigonal space group R 3c with small differences in the lattice parameters. Bridged by the three-atom single-bridge CHOO-, M ions form a three-dimensional distorted perovskite-like structure with dimethylamine (DMA) cations located in the cages of the network. Based on the magnetic data, these three 3D compounds are weak ferromagnets with the critical temperature T c = 8.5 K (1·Mn), 14.9 K (2·Co), and 35.6 K (3·Ni), and for 2·Co and 3·Ni, spin reorientation might take place at 13.1 and 14.3 K, respectively. At 1.8 K, hysteresis loops can be observed for all three compounds with the coercivity field ca. 90 Oe (1·Mn), 920 Oe (2·Co), and 320 Oe (3·Ni). The canting angles are estimated to be 0.08°, 0.5°, and 0.6° for 1·Mn, 2·Co, and 3·Ni, respectively. The magnetic coupling between MnII ions in 1·Mn was estimated based on the model developed by Rushbrook and Wood for a Heisenberg antiferromagnet on a simple cubic lattice and the best fit gives J = -0.23 cm-1. At the same time, according to molecular field theory of antiferromagnetism, the J values for compounds 1·Mn, 2·Co, and 3·Ni were estimated to be -0.32 cm -1, -2.3 cm-1, and -4.85 cm-1, respectively. The spin cant in these compounds may originate from the noncentrosymmetric character of the three-atom single-bridge CHOO-. Furthermore, amorphous materials 4·Mn238, 5·Mn450,6·Co320, and 7·Ni300 were prepared from precursors 1-3 under an argon atmosphere at different temperatures according to the thermogravimetric analyses. As an interesting result, 5·Mn450 was confirmed to be an amorphous form of Mn3O4 with a considerably large coercivity field H C = 4.1 kOe at 30 K compared to that value (250 Oe) for bulk Mn 3O4.
- Wang, Xin-Yi,Gan, Lin,Zhang, Shi-Wei,Gao, Song
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p. 4615 - 4625
(2008/10/09)
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- Thermal analysis of cobalt(II) salts with Some carboxylic acids
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The thermal analysis of CoC2O4·2H2O, Co(HCOO)2·2H2O and Co(CH3COO)2·H2O was carried out with simultaneous TG-DTG-DTA measurements under non-isothermal conditions in air and argon atmospheres. The intermediates and the end products of decomposition were characterised by X-ray diffraction and IR and UV-VIS spectroscopy. The decomposition of the studied compounds occur in several stages. The first stage of dissociation of each compound is dehydration both in air and argon. The next stages differ in air and argon. The final product of the decomposition of each compound in air is Co3O4. In argon it is a mixture of Co and CoO for cobalt(II) oxalate and cobalt(II) formate but CoO for cobalt(II) acetate.
- Ingier-Stocka,Grabowska
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p. 115 - 123
(2008/10/08)
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- COORDINATION COMPOUNDS OF Co(II) WITH 2-METHYL- AND 1,2-DIZAMETHYLBENZIMIDAZOLE.
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The synthesis is described of new coordination compounds of Co(II) with 2-methylbenzimidazole and 1,2-dimethylbenzimidazole. Salts of cobalt(II) with organic acids (formic, acetic, propionic, butyric) were investigated. IR spectra, diffractograms, electronic spectra, and magnetic properties were investigated, on the basis of which conclusions were drawn concerning the structure of the materials.
- Slyusarenko,Artemenko,Lapina,Pokhodnya,Zakharenko
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