Use of Cu2+ as a metal ion probe for the EPR study of metal complexation sites in the double sulfite CuI 2SO3.CdII SO3 .2H2O

Silva, Luciana da; Andrade, Jailson B. de; Mangrich, Antônio S.

doi:10.1590/s0103-50532007000300018

Cited by 13 publications

(13 citation statements)

References 11 publications

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Section: Epr Measurementsmentioning

confidence: 94%

“…The peaks appearing at 2θ = 33.2° (110), 35.7° (002), and 39° (111) reflections are assigned to be from the monoclinic CuO structure (JCPDS 48-1548). Based on XRD patterns of the FCM series (Figure 3c), all samples show no diffraction lines.…”

Section: Structure By Xrd and Ramanmentioning

confidence: 99%

“…Besides the signal in g = 2.1, a broad ferromagnetic resonance line may overlap the signal of Sn 4+ (SnO2 phase), Cu 2+ (CuO), and Mo 6+ (α-MoO3) with a hyperfine structure at a g value of around 1.9-2.1 (magnetic field 3.0-3.8 kG) [34][35][36], as demonstrated by the curve in Figure 5 above the main In addition, the tetrahedral coordination of iron with strong rhombic distortion or framework form appears at g = 4.3, well corresponding with Fe(III) presence in the structure [17]. Furthermore, the findings assign the g value close to 4.3 to the super exchange between Fe 3+ , Co 2+ , and Co 2+ /Co 3+ [17,[32][33][34].…”

Section: Epr Measurementsmentioning

confidence: 99%

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Styrene Oxidation to Valuable Compounds over Nanosized FeCo-Based Catalysts: Effect of the Third Metal Addition

et al. 2017

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Nanosized FeCo-based solids were prepared via distinct preparation procedures. The catalytic performances of the solids for styrene oxidation in the presence of hydrogen peroxide were evaluated. The addition of promoters in FeCo such as Sn, Mo, or Cu was also investigated. The catalysts were characterized with XRD, Raman spectroscopy, TEM, chemical analyses, EPR and SEM-EDS. Of these solids obtained via four different methods, the catalyst prepared via the NC and CM procedures enabled a partial incorporation of the Sn into the FeCo matrix forming a very active phase, namely the Heusler alloy. This was ascribed to the high initial dispersion of Sn as a promoter into the FeCo matrix, which led to available FeCoSn (FCS) particles well dispersed and stable on the catalyst surface. In the case of incorporating Mo or Cu to the nanosized FeCo catalyst, a poor stability towards leaching was observed when operating under the same reaction conditions. Cu was much less active than both Sn and Mo, mainly leading to acetophenone, ethylbenzene, 2-phenyl ethanol, 2-phenyl acetic acid, and 2-phenyl acetaldehyde products. The best catalytic results under the optimized reaction conditions, especially at 50 • C and styrene/H 2 O 2 molar ratio of 1 were achieved with nanosized FCS. This solid had a conversion of ca. 70% and selectivity for aldehydes of ca. 27%, and the selectivity for the condensation products was 29%.

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Section: Epr Measurementsmentioning

confidence: 94%

Section: Structure By Xrd and Ramanmentioning

confidence: 99%

Section: Epr Measurementsmentioning

confidence: 99%

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Styrene Oxidation to Valuable Compounds over Nanosized FeCo-Based Catalysts: Effect of the Third Metal Addition

et al. 2017

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“…On the other hand, LDH and LHS are composed of metal cations with a similar radius to that of Mg 2+ , and therefore Cu 2+ cations can be used to prepare these structures and they serve as EPR (Electron Paramagnetic Resonance) probes if they are spread along the layers [59,61,62] or on other solid compounds [63].…”

Section: Synthesis Of Ldh and Lhs With Cumentioning

confidence: 99%

Functionalization of Surfaces in Layered Double Hydroxides and Hydroxide Salt Nanoparticles

Arízaga¹,

Jiménez²,

Viruete³

et al. 2016

Functionalized Nanomaterials

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Layered double hydroxides (LDH) and layered hydroxide salts (LHS) are widely studied as matrices to design new materials with applications in several areas of science and technology. Both LDH and LHS are composed of molecular layered units with surfaces fully covered by hydroxyl groups and positive-charge residues within the layers; therefore, anions in the interlayer space are needed. Even though these anions are described as interlayer species without a covalent interaction with the molecular layered units, the substitution of hydroxyl groups is also possible; in other words, the functionalization of the surface could occur. This chapter reviews results previously published related to the functionalization phenomenon in LDH and LHS, which is not considered in most of the scientific reports of new materials derived from these compounds. In this text, the use of copper probes to study electron paramagnetic resonance spectra, reinforced with infrared spectroscopy to confirm functionalization, is described. The occurrence of functionalization instead of a simple anion exchange provides a change of properties in the final nanosized material.

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“…X-band spectra of complexes 1 and 2 were collected in frozen ethanol solutions at 77 K. Using the WINEPR SimFonia 51 program, the experimental data were simulated; both experimental and simulated spectra are presented in 46,53 The empirical g // / A // ratio can be employed to estimate the geometry distortion around Cu II centers, and values in the range of 105 to 135 cm are attributed to square-planar or octahedral (with tetragonal distortion) geometries. 54,55 Considering the electronic spectroscopy data and the values observed for complexes 1 (g // / A // = 129 cm) and 2 (g // / A // = 125 cm), it is possible to infer that both complexes present interactions with solvent molecules in the axial positions. Additionally, the g // / A // ratio also provides evidence on the degree of covalency ) and diffuse reflectance spectra (inset) of 1 (line a) and 2 (line b) in KBr.…”

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confidence: 99%

Binuclear CuII complexes as catalysts for hydrocarbon and catechol oxidation reactions with hydrogen peroxide and molecular oxygen

Martins¹,

Souza²,

Fernandez³

et al. 2010

J. Braz. Chem. Soc.

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Dois ligantes tridentados, HL1, [(2-hidroxibenzil)(2-(imidazol-2-il)etil)]amina, e HL2, [(2-hidroxibenzil)(2-(piridil-2-il)etil]amina, foram usados na síntese dos complexos binucleares [Cu 2 (L1) 2 ]Cl 2• 2H 2 O, complexo 1, e [Cu 2 (L2) 2 ] (ClO 4 ) 2• 1.5H 2 O, complexo 2, para serem empregados como catalisadores em processos de oxidação. Os complexos foram caracterizados por análise elementar e espectroscopias na região do infravermelho, ultravioleta-visível e ressonância paramagnética eletrônica. Foram também estudados por voltametria cíclica e titulação potenciométrica, a fim de caracterizar seus comportamentos em solução. A resolução da estrutura cristalina do complexo 1 mostrou um cátion binuclear contendo dois grupos fenóxido em ponte. Este arranjo possui uma distância Cu … Cu de 3.043(10) Å, similar à observada na catecol oxidase (2.90 Å). Os comportamentos catalíticos destes complexos foram investigados nas oxidações de cicloexano e de catecol. Na oxidação de cicloexano observou-se baixa atividade para ambos os complexos, que pode ser atribuída ao estereoimpedimento produzido pela falta de coplanaridade entre os anéis aromáticos do arcabouço dos ligantes, sugerindo que a aproximação entre o substrato e o centro ativo binuclear é uma etapa determinante no mecanismo da reação. Com relação à atividade de catecolase, foram observadas altas eficiências, com o complexo 2 sendo mais ativo que o complexo 1. Isto indica que o ligante piridina é capaz de estabilizar melhor o intermediário proposto para esse processo, que contém o centro Cu • 1.5H 2 O, complex 2, in order to obtain catalysts for oxidative processes. Both complexes were characterized by elemental analysis, IR, UV-Vis and EPR spectroscopies. In addition, they were studied by cyclic voltammetry and potentiometric titration in order to investigate their behavior in solution. The crystal structure of complex 1 revealed a binuclear cation where the metal centers are bridged by two phenoxo groups. This arrangement provides a Cu … Cu distance of 3.043(10) Å, which is similar to the observed for catechol oxidase (2.90 Å). The catalytic reactivities of both complexes were investigated for hydrocarbon and catechol oxidations. Complexes 1 and 2 led to low overall hydrocarbon oxidation conversion values of 6.34 % and 7.15 %, respectively. However, for complex 1, only cyclohexanol (Cy-OH) and cyclohexanone (Cy=O) were isolated as reaction products, with selectivities of 68.1% for Cy-OH. This low overall conversion is tentatively attributed to steric hindrance effects produced by the non-coplanar aromatic rings of the ligand scaffolds, which suggest that the access of the hydrocarbon molecule to the binuclear active center is a determinant step in the reaction mechanism. Investigation of catecholase activities has shown high efficiencies, with complex 2 being more active than complex 1. It indicates that the pyridine-containing ligand is able to stabilize the intermediate Cu I Cu I center which is proposed to be formed in this process. This is corroborated by t...

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Use of Cu2+ as a metal ion probe for the EPR study of metal complexation sites in the double sulfite CuI 2SO3.CdII SO3 .2H2O

Abstract: A estrutura dos sítios metálicos na rede de Cu

Cited by 13 publications

References 11 publications

Styrene Oxidation to Valuable Compounds over Nanosized FeCo-Based Catalysts: Effect of the Third Metal Addition

Styrene Oxidation to Valuable Compounds over Nanosized FeCo-Based Catalysts: Effect of the Third Metal Addition

Functionalization of Surfaces in Layered Double Hydroxides and Hydroxide Salt Nanoparticles

Binuclear CuII complexes as catalysts for hydrocarbon and catechol oxidation reactions with hydrogen peroxide and molecular oxygen

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