EPR Study of Cu(L-ILE)2, a copper-amino acid salt

Calvo, Rafael; Isérn, H.; Mesa, Manuel A.

doi:10.1016/0301-0104(85)87026-9

Cited by 25 publications

(14 citation statements)

References 21 publications

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“…When the magnitude of the exchange interaction J between neighboring Co(II) ions in the same layer is larger than the magnitude of the hyperfine coupling parameter A (| J | > | A |) , the hyperfine structure collapses and gives a single collapsed peak. This was shown by Farach et al for 1 / 2 ≤ I ≤ 5 / 2 (see also refs and 33). In this work we verified that the case for I = 7 / 2 follows the same trend observed by Farach et al for smaller I .…”

Section: Experimental Results and Analysissupporting

confidence: 68%

Structure and Magnetic Properties of Layered High-Spin Co(II)(l-threonine)₂(H₂O)₂

et al. 2003

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We report the structure and the magnetic properties of a cobalt(II) compound with the amino acid l-threonine, Co(C(4)H(8)NO(3))(2)(H(2)O)(2). It crystallizes in the orthorhombic chiral space group C222(1), with a = 5.843(5) A, b = 10.120(10) A, c = 22.36(3) A, and Z = 4. The Co(II) ion is in a deformed octahedral environment on a 2-fold symmetry axis parallel to the crystallographic axis b. It is bonded to two threonine molecules in a bidentate fashion, via one oxygen from the carboxylate end and the alpha-amino nitrogen. A water molecule occupies the third independent site. The Co(II) ions are arranged in layers with intralayer and interlayer distances of 5.84 and 11.18 A, respectively. Magnetic measurements data reflect the molecular character of a compound with weak exchange interactions. EPR measurements in polycrystalline and single-crystal samples indicate a distorted axial symmetry around the Co(II) ion, as expected from the structural results. Eigenvalues and eigenvectors of the g tensor are determined. The measured principal g values (5.81, 4.56, and 2.23) reflect a high-spin Co(II) ion, as suggested by the type of ligands and the molecular symmetry. From the incomplete collapse of the hyperfine structure we estimate 0.25 < |J| < 1.2 cm(-1) between neighboring Co(II) ions within a layer, transmitted through H-bonds. A higher limit |J'| < 0.07 cm(-1) is estimated for the exchange interactions between Co(II) ions in neighboring layers. From a global fit of a spin Hamiltonian with spin (3)/(2) to magnetization and EPR data we obtain a zero field splitting delta approximately 231 cm(-1) between the two lowest doublet states. The results are discussed in terms of the molecular and electronic structure of the compound.

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Section: Experimental Results and Analysissupporting

confidence: 68%

Structure and Magnetic Properties of Layered High-Spin Co(II)(l-threonine)₂(H₂O)₂

et al. 2003

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“…When J becomes comparable to A , the exchange may produce broadening, narrowing, or a total collapse of the hyperfine structure into a single line, depending on the strength of the interaction. This phenomenon has been observed in many other copper compounds; for instance, in single crystals of copper-amino acid salts . Based on this theory, we believe that the broad, intense, and unstructured line observed in the spectra of Figure is due to a weak spin–spin exchange interaction between paramagnetic centers, possibly Cu 2+ dimers, of the order of J ≈ A ∥ ≈ 400 MHz (≈ 20 mK).…”

Section: Resultssupporting

confidence: 64%

“…This phenomenon has been observed in many other copper compounds; for instance, in single crystals of copper-amino acid salts. 60 Based on this theory, we believe that the broad, intense, and unstructured line observed in the spectra of Figure 6 is due to a weak spin−spin exchange interaction between paramagnetic centers, possibly Cu 2+ dimers, of the order of J ≈ A ∥ ≈ 400 MHz (≈ 20 mK).…”

Section: H G H S G H S H S a I Smentioning

confidence: 87%

Electron Paramagnetic Resonance Study of Copper–Ethylenediamine Complex Ion Intercalated in Bentonite

et al. 2013

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This work reports on studies of two-dimensional networks of Cu 2+ ions, built by exchanging Na-bentonite with Cu 2+ aqueous or with the bis(ethylenediamine) complex, [Cu(C 2 H 4 (NH 2 )) 2 ] 2+ , at different concentrations of the paramagnetic center. Dilution of the magnetically active species is performed by the cointercalation of analogous diamagnetic zinc species, aqueous Zn 2+ , or complexed [Zn(C 2 H 4 (NH 2 )) 2 ] 2+ ions, with ethylenediamine in excess. Materials were characterized by X-ray diffraction, Fourier transform infrared (FT-IR) and UV−visible spectroscopy, and continuous-wave electron paramagnetic resonance (EPR). X-ray diffraction measurements indicated that the interlaminar distance in the bentonite decreases with the increase of Zn concentration in the composites. The observation of a two-component Cu 2+ EPR spectrum imply the coexistence of isolated Cu 2+ with a wellresolved hyperfine structure and spin−spin exchanged Cu 2+ dimers or clusters with an unresolved hyperfine structure. EPR spin Hamiltonian parameters of the isolated species in Cu/ethylenediamine intercalated samples are typical of axially distorted sites, sixcoordinated with bis(ethylenediamine) in the equatorial plane and with oxygen on the internal surfaces of the clay. Experimental facts indicate that the interaction between paramagnetic centers is mainly favored by two different phenomena: turbostratic disorder of clay sheets and segregation of the magnetic centers leading to interstratifications of layers.

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“…To estimate the magnitudes of the exchange coupling between neighbor copper ions in compounds I and II from the line width data we write the exchange Hamiltonian as , where the superscripts 1 and 2 denote the two symmetry-related copper sites, which are magnetically nonequivalent for an arbitrary orientation of the applied field B , and i and j indicate different unit cells.…”

Section: Epr Results and Analysismentioning

confidence: 99%

Structure, Single Crystal EPR Spectra, and Exchange Interactions in [Cu(l-proline)₂]₂·5H₂O and Cu(d,l-proline)₂·2H₂O

et al. 1999

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A new copper(II) compound, [Cu(L-proline)(2)](2).5H(2)O (C(20)Cu(2)H(42)N(4)O(13)) (called compound I) was synthesized and crystallized, and its structure was solved using X-ray methods. It is monoclinic, space group P2(1), with a = 11.187(1) Å, b = 12.172(3) Å, c = 11.661(1) Å, beta = 114.96(1) degrees, and Z = 2. There are two chemically different copper molecules (labeled A and B), both with the copper atom in a N(2)O(2) square planar coordination. Molecule type A has one water molecule in an apical position. Molecule B has water molecules in each of the two apical positions. Single-crystal EPR measurements have been performed in I and also in Cu(D,L-proline)(2).2H(2)O (compound II). From the similar angular variations of the position of the single resonance observed in both compounds, we evaluated the molecular g tensors. Interpretation of the molecular g tensors resulted in d(x)()()2(-)(y)()()2 orbital ground states. From the angular variations of the line width we calculated the magnitude of the exchange interactions coupling neighbor copper ions in each compound. In I copper ions type A at 7.25 Å are arranged in chains coupled through axial-equatorial bonds. The exchange coupling within these chains is |J/k| = 118 mK. The coupling between copper ions type B is weaker. However, the interactions between copper ions type A and B generate a three-dimensional magnetic network. Our data in compound II indicate that a superexchange pathway containing a weak hydrogen bond C-H- - -O is the path for an exchange interaction with |J'/k| = 48 mK between coppers in neighbor layers at 9.75 Å.

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EPR Study of Cu(L-ILE)2, a copper-amino acid salt

Cited by 25 publications

References 21 publications

Structure and Magnetic Properties of Layered High-Spin Co(II)(l-threonine)₂(H₂O)₂

Structure and Magnetic Properties of Layered High-Spin Co(II)(l-threonine)₂(H₂O)₂

Electron Paramagnetic Resonance Study of Copper–Ethylenediamine Complex Ion Intercalated in Bentonite

Structure, Single Crystal EPR Spectra, and Exchange Interactions in [Cu(l-proline)₂]₂·5H₂O and Cu(d,l-proline)₂·2H₂O

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EPR Study of Cu(L-ILE)2, a copper-amino acid salt

Cited by 25 publications

References 21 publications

Structure and Magnetic Properties of Layered High-Spin Co(II)(l-threonine)2(H2O)2

Structure and Magnetic Properties of Layered High-Spin Co(II)(l-threonine)2(H2O)2

Electron Paramagnetic Resonance Study of Copper–Ethylenediamine Complex Ion Intercalated in Bentonite

Structure, Single Crystal EPR Spectra, and Exchange Interactions in [Cu(l-proline)2]2·5H2O and Cu(d,l-proline)2·2H2O

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Structure and Magnetic Properties of Layered High-Spin Co(II)(l-threonine)₂(H₂O)₂

Structure and Magnetic Properties of Layered High-Spin Co(II)(l-threonine)₂(H₂O)₂

Structure, Single Crystal EPR Spectra, and Exchange Interactions in [Cu(l-proline)₂]₂·5H₂O and Cu(d,l-proline)₂·2H₂O