Metamagnetic behavior of [Ni(4ImNNH)2(NO3)2] having a ground high-spin state (4ImNNH=4-imidazolyl nitronyl nitroxide)

Aoki, Chigusa; Ishida, Takayuki; Nogami, Takashi

doi:10.1016/s1387-7003(03)00204-1

Cited by 11 publications

(5 citation statements)

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“…This geometry successively repeats along the a + b and a − b directions, owing to the symmetry, and accordingly they form a two-dimensional H-bond network parallel to the ab plane (Figure c). A detailed description on the structure of 3 has been reported elsewhere . The multiple and self-complementary H-bonds stabilize the side-by-side molecular arrangement, and therefore 1 − 4 are assumed to afford isomorphous crystals.…”

Section: Resultsmentioning

confidence: 99%

“…We have studied the crystal structures and magnetic properties of [M(4ImNNH) 2 (NO 3 ) 2 ] (M = Mn ( 1 ), Co ( 2 ), Ni ( 3 ), Cu ( 4 )) and preliminarily reported the intramolecular ferromagnetic coupling in 3 between nickel(II) and radical spins . There have been ample examples of ferrimagnets 1,2 according to the metal−radical approach .…”

Section: Introductionmentioning

confidence: 99%

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Molecular Metamagnet [Ni(4ImNNH)₂(NO₃)₂] (4ImNNH = 4-Imidazolyl Nitronyl Nitroxide) and the Related Compounds Showing Supramolecular H-Bonding Interactions

2003

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A new chelating radical ligand 4ImNNH (2-(4-imidazolyl)-4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide) was prepared, and complexation with divalent transition metal salts gave complexes, [M(4ImNNH)(2)X(2)], which showed intermolecular ferromagnetic interaction in high probability (7 out of 10 paramagnetic compounds investigated here). The nitrate complexes (X = NO(3); M = Mn (1), Co (2), Ni (3), Cu (4)) crystallize isomorphously in monoclinic space group P2(1)/a. The equatorial positions are occupied with two 4ImNNH chelates and the nitrate oxygen atoms are located at the axial positions. Magnetic measurements revealed that the intramolecular exchange couplings in 1, 2, and 4 were antiferromagnetic, while that in 3 was ferromagnetic with 2J/k(B) = +85 K, where the spin Hamiltonian is defined as H = -2J(S(1).S(2) + S(2).S(3)) based on the molecular structures determined as the linear radical-metal-radical triads. The intramolecular ferromagnetic interaction in 3 is interpreted in terms of orthogonality between the radical pi and metal dsigma orbitals. Compounds 1-3 exhibited intermolecular ferromagnetic interaction ascribable to a two-dimensional hydrogen bond network parallel to the crystallographic ab plane. Complex 3 became an antiferromagnet below 3.4 K and exhibited a metamagnetic transition on applying a magnetic field of 5.5 kOe at 1.8 K. The complexes prepared from metal halides, [M(4ImNNH)(2)X(2)] (X = Cl, Br; M = Mn, Co, Ni, Cu), showed intramolecular antiferromagnetic interactions, which are successfully analyzed based on the radical-metal-radical system. The crystal structures determined here on 1-4, [Mn(4ImNNH)(2)Cl(2)], and [Cu(4ImNNH)(2)Br(2)] always have intermolecular hydrogen bonds of H(imidazole).X(axial ligand)-M, where X = NO(3), Cl, Br. This interaction seems to play an important role in molecular packing and presumably also in magnetic coupling.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Molecular Metamagnet [Ni(4ImNNH)₂(NO₃)₂] (4ImNNH = 4-Imidazolyl Nitronyl Nitroxide) and the Related Compounds Showing Supramolecular H-Bonding Interactions

2003

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“…In contrast, the corresponding 2pyNN derivative having a 6-membered chelate ring is likely to undergo out-of-plane distortion and actually displays antiferromagnetic couplings [82,83]. Some exceptions have been reported; the complex from nickel(II) and 4-imidazolyl-NN exhibited a ferromagnetic coupling of 2J/k B = +85(3) K [84,85]. In that case, the small imidazole ring may force the O and N bite angle open in the 6-membered ring.…”

Section: Magneto-structural Relationship and Molecular Designmentioning

confidence: 99%

Molecular S = 2 High-Spin, S = 0 Low-Spin and S = 0 ⇄ 2 Spin-Transition/-Crossover Nickel(II)-Bis(nitroxide) Coordination Compounds

et al. 2021

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Heterospin systems have a great advantage in frontier orbital engineering since they utilize a wide diversity of paramagnetic chromophores and almost infinite combinations and mutual geometries. Strong exchange couplings are expected in 3d–2p heterospin compounds, where the nitroxide (aminoxyl) oxygen atom has a direct coordination bond with a nickel(II) ion. Complex formation of nickel(II) salts and tert-butyl 2-pyridyl nitroxides afforded a discrete 2p–3d–2p triad. Ferromagnetic coupling is favored when the magnetic orbitals, nickel(II) dσ and radical π*, are arranged in a strictly orthogonal fashion, namely, a planar coordination structure is characterized. In contrast, a severe twist around the coordination bond gives an orbital overlap, resulting in antiferromagnetic coupling. Non-chelatable nitroxide ligands are available for highly twisted and practically diamagnetic complexes. Here, the Ni–O–N–Csp2 torsion (dihedral) angle is supposed to be a useful metric to describe the nickel ion dislocated out of the radical π* nodal plane. Spin-transition complexes exhibited a planar coordination structure in a high-temperature phase and a nonplanar structure in a low-temperature phase. The gradual spin transition is described as a spin equilibrium obeying the van’t Hoff law. Density functional theory calculation indicates that the energy level crossing of the high- and low-spin states. The optimized structures of diamagnetic and high-spin states well agreed with the experimental large and small torsions, respectively. The novel mechanism of the present spin transition lies in the ferro-/antiferromagnetic coupling switch. The entropy-driven mechanism is plausible after combining the results of the related copper(II)-nitroxide compounds. Attention must be paid to the coupling parameter J as a variable of temperature in the magnetic analysis of such spin-transition materials. For future work, the exchange coupling may be tuned by chemical modification and external stimulus, because it has been clarified that the parameter is sensitive to the coordination structure and actually varies from 2J/kB = +400 K to −1400 K.

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“…The reason is mainly that nitronyl nitroxide radicals are the most common open-shell bridging species but very poor electron-donating groups, furthermore, hexafluoroacetylacetonate ligands act as electron-withdrawing groups, which can enhance the radical coordination ability when bound to the metal center. [6][7][8] By adopt this strategy, a wide variety of complexes have been prepared and characterized. [9][10][11][12][13] To develop the new magnetic coupling systems of 3D radicals, using a new radical NITPh-p-Br and cobalt ion, one new dimer cobalt(II) complex, Co(hfac) 2 (NITPh-p-Br) 2 , was synthesized.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Crystal Structures, and Magnetic Properties of a Cobalt Complex With Nitronyl Nitroxide Radical

Zhang

Chen

Wang

et al. 2012

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-

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Metamagnetic behavior of [Ni(4ImNNH)2(NO3)2] having a ground high-spin state (4ImNNH=4-imidazolyl nitronyl nitroxide)

Cited by 11 publications

References 16 publications

Molecular Metamagnet [Ni(4ImNNH)₂(NO₃)₂] (4ImNNH = 4-Imidazolyl Nitronyl Nitroxide) and the Related Compounds Showing Supramolecular H-Bonding Interactions

Molecular Metamagnet [Ni(4ImNNH)₂(NO₃)₂] (4ImNNH = 4-Imidazolyl Nitronyl Nitroxide) and the Related Compounds Showing Supramolecular H-Bonding Interactions

Molecular S = 2 High-Spin, S = 0 Low-Spin and S = 0 ⇄ 2 Spin-Transition/-Crossover Nickel(II)-Bis(nitroxide) Coordination Compounds

Synthesis, Crystal Structures, and Magnetic Properties of a Cobalt Complex With Nitronyl Nitroxide Radical

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Metamagnetic behavior of [Ni(4ImNNH)2(NO3)2] having a ground high-spin state (4ImNNH=4-imidazolyl nitronyl nitroxide)

Cited by 11 publications

References 16 publications

Molecular Metamagnet [Ni(4ImNNH)2(NO3)2] (4ImNNH = 4-Imidazolyl Nitronyl Nitroxide) and the Related Compounds Showing Supramolecular H-Bonding Interactions

Molecular Metamagnet [Ni(4ImNNH)2(NO3)2] (4ImNNH = 4-Imidazolyl Nitronyl Nitroxide) and the Related Compounds Showing Supramolecular H-Bonding Interactions

Molecular S = 2 High-Spin, S = 0 Low-Spin and S = 0 ⇄ 2 Spin-Transition/-Crossover Nickel(II)-Bis(nitroxide) Coordination Compounds

Synthesis, Crystal Structures, and Magnetic Properties of a Cobalt Complex With Nitronyl Nitroxide Radical

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Molecular Metamagnet [Ni(4ImNNH)₂(NO₃)₂] (4ImNNH = 4-Imidazolyl Nitronyl Nitroxide) and the Related Compounds Showing Supramolecular H-Bonding Interactions

Molecular Metamagnet [Ni(4ImNNH)₂(NO₃)₂] (4ImNNH = 4-Imidazolyl Nitronyl Nitroxide) and the Related Compounds Showing Supramolecular H-Bonding Interactions