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Magnetochemistry, Volume 1, Issue 1 (December 2015) – 7 articles , Pages 1-82

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2580 KiB  
Article
Abrupt Spin Transition and Chiral Hydrogen-Bonded One-Dimensional Structure of Iron(III) Complex [FeIII(Him)2(hapen)]SbF6 (Him = imidazole, H2hapen = N,N′-bis(2-hydroxyacetophenylidene)ethylenediamine)
by Takahiro Ueno, Kyohei Miyano, Daisuke Hamada, Hiromasa Ono, Takeshi Fujinami, Naohide Matsumoto and Yukinari Sunatsuki
Magnetochemistry 2015, 1(1), 72-82; https://doi.org/10.3390/magnetochemistry1010072 - 11 Dec 2015
Cited by 4 | Viewed by 4061
Abstract
Solvent-free spin crossover (SCO) iron(III) complex, [FeIII(Him)2(hapen)]SbF6 (Him = imidazole, H2hapen = N,N′-bis(2-hydroxyacetophenylidene)ethylenediamine), is synthesized. The FeIII ion has an octahedral coordination geometry, with N2O2 donor atoms of hapen and N [...] Read more.
Solvent-free spin crossover (SCO) iron(III) complex, [FeIII(Him)2(hapen)]SbF6 (Him = imidazole, H2hapen = N,N′-bis(2-hydroxyacetophenylidene)ethylenediamine), is synthesized. The FeIII ion has an octahedral coordination geometry, with N2O2 donor atoms of hapen and N2 atoms of two imidazoles at the axial positions. The saturated five-membered chelate ring of hapen moiety assumes a gauche-type δ- or λ-conformation to give chiral species of δ-[FeIII(Him)2(hapen)]+ or λ-[FeIII(Him)2(hapen)]+. One imidazole is hydrogen-bonded to phenoxo oxygen atom of hapen of the adjacent unit to give a hydrogen-bonded chiral one-dimensional structure, {δ-[FeIII(Him)2(hapen)]+}1∞ or {λ-[FeIII(Him)2(hapen)]+}1∞. The adjacent chains with the opposite chiralities are arrayed alternately. The temperature dependences of the magnetic susceptibilities revealed an abrupt one-step spin transition between high-spin (S = 5/2) and low-spin (S = 1/2) states at the spin transition temperature of T1/2 = 105 K. The crystal structures were determined at 296 and 100 K, where the populations of HS:LS of high- and low-spin ratio are evaluated to be 1:0 and 0.3:0.7, respectively, based on magnetic measurements. During the spin transition from 296 K to 100 K, the average Fe–N distance and O–Fe–O angle decrease to a regular octahedron by 0.16 Å and 13.4°, respectively. The structural change in the coordination environment is transmitted to the adjacent spin crossover (SCO) sites along the chiral 1D chain through hydrogen-bonds. The abrupt SCO profile and the spin transition temperature for the isomorphous compounds [FeIII(Him)2(hapen)]Y (Y = PF6, AsF6, SbF6) are ascribed to the chiral hydrogen-bonded 1D structure and chain-anion interaction. Full article
(This article belongs to the Special Issue Spin Crossover (SCO) Research)
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6402 KiB  
Article
Magnetic Behaviour of Transition Metal Complexes with Functionalized Chiral and C60-Filled Nanotubes as Bridging Ligands: A Theoretical Study
by Silvia Gómez-Coca and Eliseo Ruiz
Magnetochemistry 2015, 1(1), 62-71; https://doi.org/10.3390/magnetochemistry1010062 - 04 Dec 2015
Cited by 4 | Viewed by 3364
Abstract
Functionalized nanotubes are promising candidates to promote communication between paramagnetic centres at large distances through their highly delocalized π systems. Here, Density Functional Theory methods are employed to study the exchange coupling interaction between FeIII paramagnetic centres coordinated at terminal carboxylate ligands [...] Read more.
Functionalized nanotubes are promising candidates to promote communication between paramagnetic centres at large distances through their highly delocalized π systems. Here, Density Functional Theory methods are employed to study the exchange coupling interaction between FeIII paramagnetic centres coordinated at terminal carboxylate ligands of functionalized nanotubes. Chiral nanotubes exhibit ferromagnetic coupling at long distances while non-chiral systems usually favor antiferromagnetic coupling. The inclusion of C60 molecules inside the nanotube, resulting in peapod structures, in some cases causes dramatic changes in the coupling interactions and spin density. Full article
(This article belongs to the Special Issue Magnetochemistry: From Fundamentals to Applications)
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1483 KiB  
Article
Novel Topologies in Vanadium-bis-β-Diketone Chemistry: A [V4] and a [V6] Metallacyclophane
by Ivana Borilovic, Olivier Roubeau, Irene Fernández Vidal, Simon J. Teat and Guillem Aromí
Magnetochemistry 2015, 1(1), 45-61; https://doi.org/10.3390/magnetochemistry1010045 - 02 Dec 2015
Cited by 8 | Viewed by 4818
Abstract
Exploring the chemistry of vanadyl ions (VO2+) with bis-β-diketone ligands, in pyridine reactions of vanadyl sulfate with 1,3-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-benzene (H4L1) and 1,3-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-pyridine (H4L2), two novel clusters, [(VIVO)4(H2L1) [...] Read more.
Exploring the chemistry of vanadyl ions (VO2+) with bis-β-diketone ligands, in pyridine reactions of vanadyl sulfate with 1,3-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-benzene (H4L1) and 1,3-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-pyridine (H4L2), two novel clusters, [(VIVO)4(H2L1)4(py)4] (1) and [(VVO)4(VIVO)2 (O)4(L2)2(py)6] (2) were prepared and characterized. Due to the conformational flexibility of the ligands, both entities exhibit very peculiar metal topologies and composition, differing significantly from structural patterns established in the related chemistry of divalent 3d metals. Structural analysis also unveils the existence of the most complex metallamacrocycles from this family to date. Studies of the magnetic properties via bulk magnetization measurements and EPR spectroscopy confirmed the existence of uncoupled long-distant S = 1/2 metal centers and the spin ground states S = 2 and S = 1 of the clusters. Full article
(This article belongs to the Special Issue Magnetochemistry: From Fundamentals to Applications)
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1739 KiB  
Article
Magnetic Properties and the Superatom Character of 13-Atom Platinum Nanoclusters
by Emil Roduner and Christopher Jensen
Magnetochemistry 2015, 1(1), 28-44; https://doi.org/10.3390/magnetochemistry1010028 - 26 Nov 2015
Cited by 15 | Viewed by 5707
Abstract
13-atom platinum nanoclusters have been synthesized quantitatively in the pores of the zeolites NaY and KL. They reveal highly interesting magnetic properties like high-spin states, a blocking temperature, and super-diamagnetism, depending heavily on the loading of chemisorbed hydrogen. Additionally, EPR active states are [...] Read more.
13-atom platinum nanoclusters have been synthesized quantitatively in the pores of the zeolites NaY and KL. They reveal highly interesting magnetic properties like high-spin states, a blocking temperature, and super-diamagnetism, depending heavily on the loading of chemisorbed hydrogen. Additionally, EPR active states are observed. All of these magnetic properties are understood best if one considers the near-spherical clusters as analogs of transition metal atoms with low-spin and high-spin states, and with delocalized molecular orbitals which have a structure similar to that of atomic orbitals. These clusters are, therefore, called superatoms, and it is their analogy with normal atoms which is in the focus of the present work, but further phenomena, like the observation of a magnetic blocking temperature and the possibility of superconductivity, are discussed. Full article
(This article belongs to the Special Issue Magnetochemistry: From Fundamentals to Applications)
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1026 KiB  
Communication
Spin-Crossover Hysteresis of [FeII(LHiPr)2(NCS)2] (LHiPr = N-2-Pyridylmethylene-4-Isopropylaniline) Accompanied by Isopropyl Conformation Isomerism
by Naotaka Mochida, Akifumi Kimura and Takayuki Ishida
Magnetochemistry 2015, 1(1), 17-27; https://doi.org/10.3390/magnetochemistry1010017 - 20 Nov 2015
Cited by 14 | Viewed by 5297
Abstract
[FeII(LHiPr)2(NCS)2] (LHiPr = N-2-pyridylmethylene-4-isopropylaniline) showed an abrupt spin-crossover (SCO) at T1/2↓ = 154 K on cooling and at T1/2↑ = 167 K on heating. The thermal hysteresis [...] Read more.
[FeII(LHiPr)2(NCS)2] (LHiPr = N-2-pyridylmethylene-4-isopropylaniline) showed an abrupt spin-crossover (SCO) at T1/2↓ = 154 K on cooling and at T1/2↑ = 167 K on heating. The thermal hysteresis with a width of 13 K is related with the structural solid-state phase transition. The space group was unchanged as P21/n with Z = 8, and there are two crystallographically independent molecules in a unit cell at 130 and 180 K. The two iron (II) sites synchronously underwent the SCO. The most drastic structural change across the SCO was found in the conformation isomerization of an isopropyl group. Namely, rotation around the C(sp2)–C(sp3) bond by ca. 120° takes place during the SCO. There is no structural disorder in the high-temperature phase. The thermal hysteresis probably originates in the bulk isomerization requiring considerable activation energy in the crystalline solid. Full article
(This article belongs to the Special Issue Spin Crossover (SCO) Research)
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1824 KiB  
Article
Synthesis of 4-Hydroxy-2,6-di(pyrazol-1-yl)pyridine, and the Spin State Behaviour of Its Iron(II) Complex Salts
by Laurence J. Kershaw Cook and Malcolm A. Halcrow
Magnetochemistry 2015, 1(1), 3-16; https://doi.org/10.3390/magnetochemistry1010003 - 23 Oct 2015
Cited by 9 | Viewed by 4873
Abstract
Treatment of 4-hydroxy-2,6-dibromopyridine with four equivalent of deprotonated pyrazole in hot diglyme affords 4-hydroxy-2,6-di(pyrazol-1-yl)pyridine (L) in low yield. The three complex salts [FeL2]X2 (X = BF4, 1; X = [...] Read more.
Treatment of 4-hydroxy-2,6-dibromopyridine with four equivalent of deprotonated pyrazole in hot diglyme affords 4-hydroxy-2,6-di(pyrazol-1-yl)pyridine (L) in low yield. The three complex salts [FeL2]X2 (X = BF4, 1; X = ClO4, 2; X = PF6, 3) have been prepared, and crystallographically characterised as their methanol solvates. The solvate structures contain complexes that are fully high-spin (1 and 3), or in a mixed high:low spin state population at 150 K (2). Bulk samples of 1 and 2 obtained from methanol/diethyl ether contain a second, minor crystal phase that exhibits an abrupt spin-transition near 200 K. Recrystallisation of 1 and 2 from nitromethane/diethyl ether affords powder samples that are highly enriched in this spin-transition phase. Full article
(This article belongs to the Special Issue Spin Crossover (SCO) Research)
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276 KiB  
Editorial
Magnetochemistry: An Old Discipline with New Opportunities
by Carlos J. Gómez-García
Magnetochemistry 2015, 1(1), 1-2; https://doi.org/10.3390/magnetochemistry1010001 - 19 May 2015
Cited by 2 | Viewed by 3059
Abstract
Even if the moment is not featured in “Youtube” and the story might have not been exactly as we have been told, we can easily imagine the surprise of the Cretan shepherd named Magnes when he observed for the first time that a [...] Read more.
Even if the moment is not featured in “Youtube” and the story might have not been exactly as we have been told, we can easily imagine the surprise of the Cretan shepherd named Magnes when he observed for the first time that a black stone in the region of Magnesia (in northern Greece) attracted the iron tip of his crook almost 4000 years ago. [...] Full article
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