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- Author or Editor: Wiesława Ferenc x
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Abstract
The thermal properties of 5-chloro-2-methoxybenzoates of lanthanides(III) and Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) were studied in air and nitrogen atmospheres. The complexes were obtained as mono-, di-, tetra- and pentahydrates with a metal to ligand ratio of 1:3 (in the case of lanthanides(III)) and 1:2 (in the case of d-block elements). They have colours typical for Ln3+ and M2+ ions. All complexes are polycrystalline compounds. When heated they dehydrate to form anhydrous salts which next in air are decomposed to the oxides of the respective metals while in nitrogen to the mixtures of metal oxides, oxychlorides and carbon.
Abstact
5-Chloro-2-nitrobenzoates of Co(II), Ni(II) and Cu(II) having formulae Co(C7H3O4NCl)2·3H2O, Ni(C7H3O4NCl)2·3H2O and Cu(C7H3O4NCl)2·2H2O, were obtained as polycrystalline compounds. From the IR spectra analysis of complexes, sodium salt and according to the spectroscopic criteria the carboxylate ions seem bidentate groups. The complexes of Co(II) and Cu(II) lose the water of crystallization in one step at 363–523 K. The Ni(II) complex loses it in two stages in the ranges of 323–378 and 378–523 K, respectively. The compounds follow the Curie–Weiss law. The magnetic moment values experimentally determined change from 4.53 to 4.55 μB for Co(II) complex, from 2.34 to 2.97 μB for Ni(II) 5-chloro-2-nitrobenzoate and from 1.80 to 1.90 μB for Cu(II) complex.
Abstract
The physico-chemical properties and thermal stability in air of the light lanthanide 2,3- and 3,5-dimethoxybenzoates were studied and compared in order to observe if there is influence of the position of -OCH3 substituents in benzene ring on their properties, mainly on their thermal stability. The complexes of both of two series are crystalline, hydrated or anhydrous salts with colours typical of Ln3+ ions. The carboxylate group shows the different coordination modes. It may coordinate as a bidentate, chelating or tridentate chelating-bridging ligand. The thermal stabilities of 2,3- and 3,5-dimethoxybenzoates of light lanthanides were studied in the temperature range 293-1173 K. The solubilities of 2,3- and 3,5-dimethoxybenzoates of these elements in water at room temperature are in the orders of 10-3-10-2 mol dm-3 and 10-4 mol dm-3, respectively. The various positions of -OCH3 groups in benzene ring influences some physico-chemical properties of these compounds.
Abstract
Four new complexes of 2,3,4-trimethoxybenzoic acid anion with manganese(II), cobalt(II), nickel(II) and copper(II) cations were synthesized, analysed and characterized by standard chemical and physical methods. 2,3,4-Trimethoxybenzoates of Mn(II), Co(II), Ni(II) and Cu(II) are polycrystalline compounds with colours typical for M(II) ions. The carboxylate group in the anhydrous complexes of Mn(II), Co(II) and Ni(II) is monodentate and in that of Cu(II) monohydrate is bidentate bridging one. The anhydrous complexes of Mn(II), Co(II) and Ni(II) heated in air to 1273 K are stable up to 505–517 K. Next in the range of 505–1205 K they decompose to the following oxides: Mn3O4, CoO, NiO. The complex of Cu(II) is stable up to 390 K, and next in the range of 390–443 K it loses one molecule of water. The final product of its decomposition is CuO. The solubility in water at 293 K is of the order of 10–3 mol dm–3 for the Mn(II) complex and 10–4 mol dm–3 for Co(II), Ni(II) and Cu(II) complexes. The magnetic moment values of Mn2+, Co2+, Ni2+ and Cu2+ ions in 2,3,4-trimethoxybenzoates experimentally determined in the range of 77–300 K change from 5.64–6.57 μB (for Mn2+), 4.73–5.17 μB (for Co2+), 3.26–3.35 μB (for Ni2+) and 0.27–1.42 μB (for Cu2+). 2,3,4-Trimethoxybenzoates of Mn(II), Co(II) and Ni(II) follow the Curie–Weiss law, whereas that of Cu(II) forms a dimer.
Complexes of the selected transition metal ions with 4-methoxycinnamic acid
Physico-chemical properties
Abstract
In this study, 4-methoxycinnamates of Mn(II), Co(II), Ni(II), Cu(II), Cd(II), Nd(III) and Gd(III) were synthesised. From the infrared (IR) spectra analysis of complexes, sodium salt and according to the spectroscopic criteria the carboxylate groups seem to be bidentate chelating. The complexes of 4-methoxycinnamates lose the water molecules in one or two steps. The final products of their decomposition are oxides of the respective metals. The enthalpy values of dehydration process were determined. The FTIR spectra of the gas phase products indicate that the decomposition of the complexes is connected mainly with the release of molecules of water (H2O), carbon dioxide (CO2), carbon monoxide (CO), methane (CH4) and other hydrocarbons. The analysed compounds follow the Curie–Weiss law. The magnetic moment values experimentally determined change as follows: from 5.90 μ B to 6.27 μ B for Mn(II) complex, from 4.57 μ B to 4.99 μ B for Co(II) complex, from 3.68 μ B to 3.30 μ B for Ni(II) complex, from 1.87 μ B to 1.96 μ B for Cu(II) complex, from 3.06 μ B to 3.51 μ B for Nd(III) complex, and from 6.91 μ B to 6.90 μ B for Gd(III) complex.
The complexes of 3,5-dimethoxybenzoates of Co(II), Ni(II) and Cu(II) have been synthesized as hydrated polycrystalline solids and characterized by elemental analysis, IR, FIR and electronic spectroscopy, magnetic studies and X-ray diffraction measurements. They possess colours typical of the M(II) ions: Cu-blue, Ni-green, Co-pink. The carboxylate groups bind as monodentate or a symmetrical, bidentate chelating or bridging ligands. The thermal stabilities were determined in air. When heated they dehydrate to form anhydrous salts which are decomposed to the oxides of respective metals. The magnetic susceptibilities of the complexes were measured over the range 77-300 K and the magnetic moments were calculated. The results reveal the complexes of Ni(II) and Co(II) to be high-spin complexes and that of Cu(II) to form dimer.
Abstract
4-Chloro-2-methoxybenzoates of light lanthanides(III) were obtained as mono-, di-or trihydrates with metal to ligand ratio of 1:3 and general formula Ln(C8H6ClO3)3·nH2O, where n=1 for Ln=Ce, Pr, n=2 for Ln=Nd, Sm, Eu, Gd and n=3 for Ln=La. The complexes were characterized by elemental analysis, IR spectra, thermogravimetric studies, X-ray diffraction and magnetic measurements. The carboxylate group appears to be a symmetrical bidentate, chelating ligand. All complexes seem polycrystalline compounds. Their thermal stabilities were determined in air. When heated they dehydrate to form anhydrous salts which next are decomposed to the oxides of the respective metals. The solubilities of light lanthanide(III) 4-chloro-2-methoxybenzoates in water at 293 K are of the order of 10−5 mol dm−3. The magnetic moments were determined over the range of 77–300 K. They obey the Curie-Weiss law. The values of μeff calculated for all compounds are close to those obtained for Ln3+ by Hund and Van Vleck. The results indicate that there is no influence of the ligand field of 4f electrons on lanthanide ions and the metal ligand bonding is mainly electrostatic in nature.
Abstract
Physico-chemical properties of 4-chloro-2-nitrobenzoates of Co(II), Ni(II), and Cu(II) were studied. The complexes were obtained as mono- and trihydrates with a metal ion to ligand ratio of 1:2. All analysed 4-chloro-2-nitrobenzoates are polycrystalline compounds with colours depending on the central ions: pink for Co(II), green for Ni(II), and blue for Cu(II) complexes. Their thermal decomposition was studied only in the range of 293–523 K, because it was found that on heating in air above 523 K 4-chloro-2-nitrobenzoates decompose explosively. Hydrated complexes lose crystallization water molecules in one step and anhydrous compounds are formed. The final products of their decomposition are the oxides of the respective transition metals. From the results it appears that during dehydration process no transformation of nitro group to nitrite takes place. The solubilities of analysed complexes in water at 293 K are of the order of 10–4–10–2 mol dm–3. The magnetic moment values of Co2+, Ni2+ and Cu2+ ions in 4-chloro-2-nitrobenzoates experimentally determined at 76–303 K change from 3.89 to 4.82 μB for Co(II) complex, from 2.25 to 2.98 μB for Ni(II) 4-chloro-2-nitrobenzoate, and from 0.27 to 1.44 μB for Cu(II) complex. 4-chloro-2-nitrobenzoates of Co(II), and Ni(II) follow the Curie–Weiss law. Complex of Cu(II) forms dimer.
Abstract
In this study, simultaneous TG/DTG-DTA technique was used for two cobalt(II) complexes with neocuproine(neoc) and the anion of a substituted salicylaldehyde ligand (X-salo) (X = 3-OCH3, or 5-CH3) with the general formula [Co(X-salo)2(neoc)], to determine their thermal degradation in inert atmosphere, which was found to be a multi-step decomposition related to the release of the ligand molecules. The solid material at 1300 °C (verified with PXRD) was a mixture of carbonaceous metal cobalt. Evolved gas analysis by coupled TG-MS verified the elimination of a formaldehyde molecule in the first decomposition stage, initially proposed by the percentage mass loss data. By single-crystal X-ray diffraction analysis an octahedral geometry of the complex [Co(3-OCH3-salo)2(neoc)] was found. The variable temperature magnetic susceptibility measurements showed a paramagnetic nature of the complexes, in accordance with their molecular structure. Finally, for the determination of the activation energy (E) two different methods (the isoconversional methods of Ozawa, Flynn and Wall (OFW) and Friedman) were used comparatively.
