Magnetochemistry

1020 KiB

Open AccessArticle

Low Field NMR Determination of pKa Values for Hydrophilic Drugs for Students in Medicinal Chemistry

by Aleksandra Zivkovic, Jan Josef Bandolik, Alexander Jan Skerhut, Christina Coesfeld, Miomir Raos, Nenad Zivkovic, Vlastimir Nikolic and Holger Stark

Magnetochemistry 2017, 3(3), 29; https://doi.org/10.3390/magnetochemistry3030029 - 20 Sep 2017

Cited by 9 | Viewed by 6906

Abstract

For an interdisciplinary approach on different topics of medicinal and analytical chemistry, we applied a known experimental pKa value determination method on the field of the bench top nuclear magnetic resonance (NMR) spectrometry of some known biologically active pyridine-based drugs, i.e., pyridoxine [...] Read more.

For an interdisciplinary approach on different topics of medicinal and analytical chemistry, we applied a known experimental pKa value determination method on the field of the bench top nuclear magnetic resonance (NMR) spectrometry of some known biologically active pyridine-based drugs, i.e., pyridoxine hydrochloride, isoniazid, and nicotine amide. The chemical shifts of the aromatic ring protons in the ¹H NMR spectrum change depending on the protonation status. The data were analyzed on dependence of the chemical shifts by different pH (pD) environments and then the pKa values were calculated. The pKa values obtained were in agreement with the literature data for the compounds, searched by the students on web programs available at our university. The importance of the pKa values in protein-ligand interactions and distribution etc. of drugs was brought up to the students’ attention. In addition, by the use of a free web application for pKa values prediction, students calculated the predicted modeled pKa value. The experimental and in-silico approaches enhance the tool box for undergraduate students in medicinal chemistry. Full article

(This article belongs to the Special Issue Nuclear Magnetic Resonance Spectroscopy)

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5613 KiB

Open AccessArticle

Critical Behavior of La_0.8Ca_0.2Mn_1−xCo_xO₃ Perovskite (0.1 ≤ x ≤ 0.3)

by Dorra Turki, Zafar Khan Ghouri, Saeed Al-Meer, Khaled Elsaid, M. I. Ahmad, Ahmed Easa, Gyorgy Remenyi, Sami Mahmood, El Kebir Hlil, Mohamed Ellouze and Foued Elhalouani

Magnetochemistry 2017, 3(3), 28; https://doi.org/10.3390/magnetochemistry3030028 - 19 Sep 2017

Cited by 14 | Viewed by 4983

Abstract

The critical properties of La_0.8Ca_0.2Mn_1−xCo_xO₃ (x = 0, 0.1, 0.2 and 0.3) compounds were investigated by analysis of the magnetic measurements in the vicinity of their critical temperature. Arrott plots revealed that the paramagnetic [...] Read more.

The critical properties of La_0.8Ca_0.2Mn_1−xCo_xO₃ (x = 0, 0.1, 0.2 and 0.3) compounds were investigated by analysis of the magnetic measurements in the vicinity of their critical temperature. Arrott plots revealed that the paramagnetic PM-ferromagnetic (FM) phase transition for the sample with x = 0 is a first order transition, while it is a second order transition for all doped compounds. The critical exponents β, γ and δ were evaluated using modified Arrott plots (MAP) and the Kouvel-Fisher method (KF). The reliability of the evaluated critical exponents was confirmed by the Widom scaling relation and the universal scaling hypothesis. The values of the critical exponents for the doped compounds were consistent with the 3D-Heisenberg model for magnetic interactions. For x = 0.1, the estimated critical components are found inconsistent with any known universality class. In addition, the local exponent n was determined from the magnetic entropy change and found to be sensitive to the magnetic field in the entire studied temperature range. Full article

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9289 KiB

Open AccessArticle

Effect of Twisting and Stretching on Magneto Resistance and Spin Filtration in CNTs

by Anil Kumar Singh and Sudhanshu Choudhary

Magnetochemistry 2017, 3(3), 27; https://doi.org/10.3390/magnetochemistry3030027 - 24 Aug 2017

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Abstract

Spin-dependent quantum transport properties in twisted carbon nanotube and stretched carbon nanotube are calculated using density functional theory (DFT) and non-equilibrium green’s function (NEGF) formulation. Twisting and stretching have no effect on spin transport in CNTs at low bias voltages. However, at high [...] Read more.

Spin-dependent quantum transport properties in twisted carbon nanotube and stretched carbon nanotube are calculated using density functional theory (DFT) and non-equilibrium green’s function (NEGF) formulation. Twisting and stretching have no effect on spin transport in CNTs at low bias voltages. However, at high bias voltages the effects are significant. Stretching restricts any spin-up current in antiparallel configuration (APC), which results in higher magneto resistance (MR). Twisting allows spin-up current almost equivalent to the pristine CNT case, resulting in lower MR. High spin filtration is observed in PC and APC for pristine, stretched and twisted structures at all applied voltages. In APC, at low voltages spin filtration in stretched CNT is higher than in pristine and twisted ones, with pristine giving a higher spin filtration than twisted CNT. Full article

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166 KiB

Open AccessEditorial

Molecular Magnetism of Lanthanides Complexes and Networks

by Kevin Bernot

Magnetochemistry 2017, 3(3), 26; https://doi.org/10.3390/magnetochemistry3030026 - 2 Aug 2017

Cited by 1 | Viewed by 3363

Abstract

Lanthanides ions allows for the design of remarkable magnetic compounds with unique magnetic properties.[...] Full article

(This article belongs to the Special Issue Molecular Magnetism of Lanthanides Complexes and Networks)

3928 KiB

Open AccessArticle

Mapping the Magnetic Anisotropy inside a Ni₄ Cubane Spin Cluster Using Polarized Neutron Diffraction

by Olga Iasco, Yuri Chumakov, Frédéric Guégan, Béatrice Gillon, Marc Lenertz, Alexandre Bataille, Jean-François Jacquot and Dominique Luneau

Magnetochemistry 2017, 3(3), 25; https://doi.org/10.3390/magnetochemistry3030025 - 13 Jul 2017

Cited by 7 | Viewed by 4191

Abstract

In this publication, we report on the study of the magnetic anisotropy of the cubane type tetranuclear cluster of Ni(II), [Ni₄(L)₄(MeOH)₄] (H₂L = salicylidene-2-ethanolamine; MeOH = methanol), by the means of angular-resolved magnetometry and polarized [...] Read more.

In this publication, we report on the study of the magnetic anisotropy of the cubane type tetranuclear cluster of Ni(II), [Ni₄(L)₄(MeOH)₄] (H₂L = salicylidene-2-ethanolamine; MeOH = methanol), by the means of angular-resolved magnetometry and polarized neutron diffraction (PND). We show that better than other usual characterization techniques—such as electron paramagnetic resonance spectroscopy (EPR) or SQUID magnetometry—only PND enables the full determination of the local magnetic susceptibility tensor of the tetranuclear cluster and those of the individual Ni(II) ions and the antiferromagnetic pairs they form. This allows highlighting that, among the two antiferromagnetic pairs in the cluster, one has a stronger easy-axis type anisotropy. This distinctive feature can only be revealed by PND measurements, stressing the remarkable insights that they can bring to the understanding of the magnetic properties of transition metals clusters. Full article

(This article belongs to the Special Issue Transition Metal Magnetism)

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3768 KiB

Open AccessArticle

The Effect of a Multiphase Microstructure on the Inverse Magnetocaloric Effect in Ni–Mn–Cr–Sn Metamagnetic Heusler Alloys

by Paweł Czaja, Robert Chulist, Antoni Żywczak, Lukasz Hawelek and Janusz Przewoźnik

Magnetochemistry 2017, 3(3), 24; https://doi.org/10.3390/magnetochemistry3030024 - 6 Jul 2017

Cited by 8 | Viewed by 4339

Abstract

Two Ni–Mn–Sn alloys substituted with 0.5 and 1 at.% Cr have been studied. The first alloy shows an average composition of Ni_49.6Mn_37.3Cr_0.7Sn_12.4 (e/a = 8.107), whereas the second has a multiphase microstructure with the matrix [...] Read more.

Two Ni–Mn–Sn alloys substituted with 0.5 and 1 at.% Cr have been studied. The first alloy shows an average composition of Ni_49.6Mn_37.3Cr_0.7Sn_12.4 (e/a = 8.107), whereas the second has a multiphase microstructure with the matrix phase of an average Ni_52.4Mn_32.7Cr₁Sn₁₄ composition (e/a = 8.146). Both alloys undergo a reversible martensitic phase transformation. The Ni_49.6Mn_37.3Cr_0.7Sn_12.4 alloy transforms to the martensite phase at 239 K and, under the magnetic field change of μ₀·ΔH = 1.5 T, gives the magnetic entropy change equal to 7.6 J/kg·K. This amounts to a refrigerant capacity in the order of 48.6 J/kg, reducible by 29.8% due to hysteresis loss. On the other hand, the alloy with a multiphase microstructure undergoes the martensitic phase transformation at 223 K with the magnetic entropy change of 1.7 J/kg·K (1 T). Although the latter spreads over a broader temperature window in the multiphase alloy, it gives much smaller refrigerant capacity of 16.2 J/kg when compared to Ni_49.6Mn_37.3Cr_0.7Sn_12.4. The average hysteresis loss for a field change of 1.5 T in the multiphase alloy is 2.7 J/kg, reducing the effective refrigerant capacity by 16.7%. These results illustrate that the key to gaining a large effective refrigerant capacity is the synergy between the magnitude of the magnetic entropy change and its broad temperature dependence. Full article

(This article belongs to the Special Issue Magnetocaloric and Electrocaloric Materials for Solid State Refrigeration)

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167 KiB

Open AccessEditorial

Magnetism of Molecular Conductors

by Manuel Almeida

Magnetochemistry 2017, 3(3), 23; https://doi.org/10.3390/magnetochemistry3030023 - 27 Jun 2017

Cited by 1 | Viewed by 2911

Abstract

The study of the magnetic properties of molecular conductors has experienced, during the last decades, a very significant evolution, comprising systems of increasing molecular complexity and moving towards multifunctional materials, namely by their incorporation in conducting networks of different paramagnetic centers.[...] Full article

(This article belongs to the Special Issue Magnetism of Molecular Conductors)

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Magnetochemistry, Volume 3, Issue 3 (September 2017) – 7 articles

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