Transition Ion Data Tabulation

Misra, Sushil K.

doi:10.1007/978-1-4612-1486-1_8

Cited by 2 publications

(8 citation statements)

References 61 publications

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“…The g-factors of the two studied samples (Figure 4) coincided: g = 2.02. This is consistent with the literature data, 33 which makes it possible to attribute this signal to manganese ions. In all of the spectra, six lines responsible for the hyperfine interaction (HFI) with the 55 Mn nucleus (I = 5/2) are dominated.…”

Section: Electronic Paramagnetic Resonance (Epr)supporting

confidence: 93%

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Annealing-Induced Structural Behavior of Mn Dopant Ions in Calcium Orthovanadate Ca₃(VO₄)₂ Single Crystals

et al. 2022

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The crystal and local structures of Czochralski-grown calcium orthovanadate (Ca 3 (VO 4 ) 2 ) single crystals doped with over-stoichiometric 0.05 wt % Mn 2 O 3 (CVO:0.05Mn) and annealed under different conditions are studied by singlecrystal conventional and synchrotron X-ray diffraction, X-ray absorption spectroscopy, and electron paramagnetic resonance for the first time. Bottom (annealing in air) and top (annealing in air and in vacuum) parts of the CVO:0.05Mn crystal differ in the manganese content (higher in the bottom part), formal charge (Mn 4+ and Mn (3+δ)+ , respectively), and color (orange bottom part; light orange and yellow top parts annealed in air and vacuum, respectively). Manganese ions are located in one (Ca3, distorted two-capped trigonal prism) of five crystallographic Ca sites and have octahedral coordination, which is consistent with crystal-chemical properties of transition-metal ions. The presence of vacancies in one of three V sites is revealed. Formal charge 5+ for vanadium ions is confirmed by X-ray photoelectron spectroscopy. Different colors of CVO:Mn crystals and different formal charges of manganese are explained depending on the growth and post-growth treatment conditions.

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Section: Electronic Paramagnetic Resonance (Epr)supporting

confidence: 93%

“…32 Extensive bibliographic information on the EPR parameters of manganese ions in various valence states (II, III, IV, V) was collected. 33 EPR spectra for CVO:0.05Mn samples (air, top or bottom) (Table 1) are shown in Figure 4 (X and Q-bands).…”

Section: Electronic Paramagnetic Resonance (Epr)mentioning

confidence: 99%

Annealing-Induced Structural Behavior of Mn Dopant Ions in Calcium Orthovanadate Ca₃(VO₄)₂ Single Crystals

et al. 2022

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“…Although a similar result was obtained recently for two gadolinium cryptate complexes in solution, this finding seems physically unlikely. In the solid, high-order terms are usually much smaller unless the second order vanishes because of an octahedral or higher symmetry, which is clearly not the case here.…”

Section: Resultsmentioning

confidence: 78%

“…There is some experimental evidence for such an isotropy in the solid state for Gd 3+ doped into various diamagnetic matrices. 39 The reported anisotropies are fairly small (0.01 > |g max -g min | > 0.0001) but can provide an efficient relaxation mechanism when the external magnetic field is high enough. A straightforward application of Refield's relaxation theory, combined with Rast's work on the ZFS modulation processes, leads to the relaxation matrices presented in the Appendix.…”

Section: Resultsmentioning

confidence: 93%

“…This mechanism (with an associated hyperfine tensor anisotropy) is often invoked to explain the electron spin relaxation of S = 1 / 2 species, either organic radicals or transition metal ion complexes. There is some experimental evidence for such an isotropy in the solid state for Gd 3+ doped into various diamagnetic matrices . The reported anisotropies are fairly small (0.01 > | g max − g min | > 0.0001) but can provide an efficient relaxation mechanism when the external magnetic field is high enough.…”

Section: Resultsmentioning

confidence: 99%

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Multiple-Frequency EPR Spectra of Two Aqueous Gd³⁺Polyamino Polypyridine Carboxylate Complexes: A Study of High Field Effects

et al. 2007

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In the search for highly efficient magnetic resonance imaging contrast agents, polyamino polypyridine carboxylate complexes of Gd 3+ have shown unusual properties with both very rapid and very slow electron spin relaxation in solution observed by electron paramagnetic resonance. Since the relationship between the molecular structure and the electron spin properties remains quite obscure at this point, detailed studies of such complexes may offer useful clues for the design of Gd 3+ compounds with tailored electronic features. Furthermore, the availability of very high-frequency EPR spectrometers based on quasi-optical components provides us with an opportunity to test the existing relaxation theories at increasingly high magnetic fields and observation frequencies. We present a detailed EPR study of two gadolinium polyamino polypyridine carboxylate complexes, [Gd(tpaen)] -and [Gd(bpatcn)(H 2 O)], in liquid aqueous solutions at multiple temperatures and frequencies between 9.5 and 325 GHz. We analyze the results using the model of random zero-field splitting modulations through Brownian rotation and molecular deformations. We consider the effect of concentration on the line width, as well as the possible existence of an additional g-tensor modulation relaxation mechanism and its possible impact on future experiments. We use 17 O NMR to characterize the water exchange rate on [Gd(bpatcn)(H 2 O)] and find it to be slow (∼0.6 × 10 6 s -1 ). IntroductionGd 3+ complexes with multidentate ligands are routinely used in medicine as contrast agents for magnetic resonance imaging (MRI). They accelerate the magnetic relaxation of the water protons due to random modulations of the interaction with the seven unpaired electrons of the Gd 3+ center. This effect is usually quantified by the relaxiVity, namely, the longitudinal relaxation rate enhancement observed in the presence of a unit concentration (1 mM) of the paramagnetic agent. Of course, understanding the molecular origins of this enhancement is the key to developing new and improved contrast agents. Therefore, the magnetic properties of these complexes have been probed using a number of techniques, such as 1 H NMR (in the form of nuclear magnetic relaxation dispersion -NMRD), 17 O NMR, 1,2 and electron paramagnetic resonance (EPR). [3][4][5][6][7] Due to the toxicity of the [Gd(H 2 O) 8 ] 3+ aqua ion, it is necessary to embed the Gd 3+ ion in highly stable chelates for the development of potential contrast agents. The ligands are generally polyaminocarboxylates, the basic example of which is the well-known hexadentate edta 4-(ethylene diamine tetracarboxylate). However, a higher denticity is usually necessary to achieve sufficient stability. The commercial contrast agent ligands (dota 4-, dtpa 5-, dtpa-bma 3-, hp-do3a 3-) occupy eight coordination sites around the metal, leaving only one available position for a water molecule. This reduced hydration number has an obvious negative impact on relaxivity, as the chemical exchange of water molecules bound to the paramagnet...

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Transition Ion Data Tabulation

Cited by 2 publications

References 61 publications

Annealing-Induced Structural Behavior of Mn Dopant Ions in Calcium Orthovanadate Ca₃(VO₄)₂ Single Crystals

Annealing-Induced Structural Behavior of Mn Dopant Ions in Calcium Orthovanadate Ca₃(VO₄)₂ Single Crystals

Multiple-Frequency EPR Spectra of Two Aqueous Gd³⁺Polyamino Polypyridine Carboxylate Complexes: A Study of High Field Effects

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Transition Ion Data Tabulation

Cited by 2 publications

References 61 publications

Annealing-Induced Structural Behavior of Mn Dopant Ions in Calcium Orthovanadate Ca3(VO4)2 Single Crystals

Annealing-Induced Structural Behavior of Mn Dopant Ions in Calcium Orthovanadate Ca3(VO4)2 Single Crystals

Multiple-Frequency EPR Spectra of Two Aqueous Gd3+Polyamino Polypyridine Carboxylate Complexes: A Study of High Field Effects

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Annealing-Induced Structural Behavior of Mn Dopant Ions in Calcium Orthovanadate Ca₃(VO₄)₂ Single Crystals

Annealing-Induced Structural Behavior of Mn Dopant Ions in Calcium Orthovanadate Ca₃(VO₄)₂ Single Crystals

Multiple-Frequency EPR Spectra of Two Aqueous Gd³⁺Polyamino Polypyridine Carboxylate Complexes: A Study of High Field Effects