Realization of Unusual Ligand Binding Motifs in Metalated Container Molecules: Synthesis, Structures, and Magnetic Properties of the Complexes [(LMe)Ni2(μ‐L′)]n+ with L′=NO3−, NO2−, N3−, N2H4, Pyridazine, Phthalazine, Pyrazolate, and Benzoate

Hausmann, J. Niklas; Klingele, Marco H.; Lozan, Vasile; Steinfeld, Gunther; Siebert, D.; Journaux, Yves; Girerd, J.‐J.; Kersting, Berthold

doi:10.1002/chem.200305705

Cited by 70 publications

(66 citation statements)

References 114 publications

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“…[11] A particularly strong antiferromagnetic coupling of around À100 cm À1 has been observed for some 1D chain complexes with a trans-{Ni-(m 1,3 -N 3 )-Ni} motif featuring acute Ni-N-N angles (120.9 or 115.6/116.88, respectively) and a large f (180 or 175.58, respectively), [11,13] or in a dinickel(ii) complex with extremely obtuse Ni-N-N angles of 109.98. [14] Similar correlations appear also to be valid for m 3 -or m 4 -azide linkages. [7] In the case of 1 the Ni1-N3-N4 angles are quite acute and are similar at 133 K [120.7(3)8] and 253 K [116.7(3)8], whereas the torsion Ni-NNN-Ni differs dramatically [4.3(4) versus À46.6(4)8].…”

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confidence: 68%

Hysteretic Magnetic Bistability Based on a Molecular Azide Switch

et al. 2005

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Dedicated to Professor Gottfried Huttner on the occasion of his 68th birthdayMaterials that exhibit hysteretic bistability at temperatures not too far from ambient conditions are expected to have great potential for future memory or sensing applications. [1] The two relatively stable states should be clearly distinguished by their physical properties, such as their magnetic or optical characteristics. Thermal magnetic hysteresis with an abrupt and rapid property change around room temperature is particularly rare for molecule-based materials, [2] with spincrossover compounds providing the most prominent examples.[3] More recently, magnetic hysteresis has also been observed for some molecular organic radicals [4] or transition metal coordination compounds, [5,6] where switching between two states occurs through a thermal phase transition with orientational changes in the 3D crystal lattice. Herein, we report thermal hysteresis of the magnetic susceptibility for single crystals of the molecular dinickel(ii) complex [LNi 2 (N 3 ) 3 ] (1), in which a m 1,3 -azido ligand functions as an on/off switch for the intramolecular antiferromagnetic coupling between the two metal ions.Pyrazolate-based compartmental ligands such as L À , which bears thioether side-arms, have previously proven suitable as dinucleating scaffolds for the synthesis of preorganized azidonickel(ii) complexes that can serve as modules for the assembly of oligonuclear species or 1D extended chain compounds; [7] the bimetallic complex 1 was prepared as a potential building block in this context. Single crystals of 1 were grown from acetone/hexane, and an initial X-ray crystallographic analysis was carried out at 133 K (Figure 1).[8] As anticipated, both nickel ions in the C 2 -symmetric array are nested within their respective ligand compartment (with two sulfur and one nitrogen donors from the ligand side-arm) and are spanned by the bridging pyrazolate. A m 1,3 -azido bridge is found within the bimetallic pocket, and an additional terminal azide fills the remaining site at each of the six-coordinate metal ions.Since 1 did not exhibit any unusual structural features at this stage, the temperature dependence of its magnetic susceptibility was highly unexpected. The product c m T for a polycrystalline sample of 1 is depicted in Figure 2 for both decreasing and increasing temperature. The value of 1.82 cm 3 K mol À1 at 300 K is somewhat lower then the spinonly value expected for two uncoupled high-spin nickel(ii) ions (2.14 cm 3 K mol À1 for g = 2.07), and decreases only slightly upon lowering the temperature to 220 K. At 215 K, however, an abrupt drop of c m T occurs (centered at T fl = 212 K), followed by a much more rapid decline at lower temperatures; below 50 K c m T tends towards zero. The lowtemperature data are indicative of strong antiferromagnetic coupling and an S = 0 ground state, while coupling is apparently only weak above 220 K. c m T shows an analogous behavior when measured as a function of increasing temperature, but exhibits therma...

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confidence: 68%

Hysteretic Magnetic Bistability Based on a Molecular Azide Switch

et al. 2005

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“…Mold. 2013, 8 (1), [58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77] ) at 0.71 V, and iii) the oxidation of the thiophenolate sulfur atoms yielding a nickel bound thiyl radical at 1.59 V. Anodic shifts in the second and third redox waves are clearly discernible, confi rming the above fi ndings that the electron transfer events of the ferrocenyl moiety and the binuclear subunit infl uence one another. The fact that the potential shifts are not so pronounced than in 9 is in good agreement with the smaller positive charges of the participating species.…”

Section: Scheme 5 Assignment Of Redox Processes In 9-11 and 14mentioning

confidence: 99%

Dinuclear Complexes as Building Blocks for Tetra-Nuclear Macrocyclic Complexes with Dithiolate Macrocyclic Ligand

Lozan¹

2013

ChemJMold

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A series of novel tri-, tetra-and pentanuclear complexes composed of dinuclear LM 2 units (M=Co, Ni, Zn; L=24-membered macrocyclic hexaaza-dithiophenolate ligand) and ferrocene-carboxylate ([CpFeC 5 H 4 CO 2 ]ˉ), 1,1'-ferro-cenedicarboxylate ([Fe(C 5 Keywords: coordination chemistry, amino-thiophenolate ligands, di-and tetranuclear complexes, ferrocene and naphthalene diimide derivatives, polynuclear complexes IntroductionThe chemistry of container molecules has developed extensively over the past two decades. Many container molecules such as calixarenes, resorcarenes, cyclodextrins, carcerands and glycourils have been invaluable in studying the fundamental principles of inclusion phenomena and consequently their use in separation science or drug delivery, as two examples of application. Importantly, the area has attracted interest in the field of supramolecular chemistry because the properties of such host-guest compounds are often different from those of their constituent components. By adjusting the size and form of the binding cavity it is often possible to complex co-ligands in unusual coordination modes, to activate and transform small molecules, or to stabilize reactive intermediates [1,2]. One subclass are the metallated container molecules, in which metal ions and clusters are used as both a point of recognition and to give the container a well-defined structure. Such compounds also allow for an interplay of molecular recognition and transition-metal catalysis, and for the construction of more effective enzyme mimics. Of interest to the present work is the ability of metallocavitands to recognize and encapsulate difunctionalised molecules towards stabilising or enhancing the optical and electronic properties of redox-and photo-active compounds within a confined environment set up by two hemispheres.The carboxylate group, RCO 2-, can bind to transition metals in a variety of coordination modes giving rise to complexes of great structural diversity [3]. Current activities focus on the coordination chemistry of polycarboxylate ligands, as these offer great potential in the construction of polynuclear aggregates [4] and extended coordination polymers with micro-and mesoporous structures [5][6][7][8] or catalytic properties [9]. In addition, polycarboxylate ligands are of importance as spin-coupling bridging ligands [10][11][12][13][14][15][16][17] in the rapidly expanding fi eld of molecular magnetism [18, 19]. In this context, an enormous amount of literature has been generated concerning the distance dependence of magnetic exchange interactions between metal atoms linked by extended dicarboxylate ligands. Dinuclear copper complexes bridged by oxalate [20, 21] and terephthalate [22][23][24] dianions form, by far, the largest group of such systems, and it appears that the exchange interactions depend on the M···M distance [25], the relative orientation of the magnetic orbitals [26], and the degree of conjugation of the organic spacer unit [27, 28].

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“…[16] For dinickel(II) complexes [Ni II 2L 1 (-L')] + , for example, the spins on the Ni(II) ions couple ferromagnetically if the average Ni-S-Ni angles are at ~ 90 ± 5°. [18][19][20][21] For smaller or larger angles, the orthogonality of the magnetic orbitals will be cancelled thereby giving rise to superexchange interactions via one of the ligands orbitals only. Since those processes usually give rise to the antiferromagnetic exchange interaction between the metal centers, thus with increasing deviation from the 90° bonding geometry the antiferromagnetic contributing to the total exchange will grow and produce a change of the sign of J.…”

Section: Introductionmentioning

confidence: 99%

“…For [Ni2L 1 (-L')] + complexes, the most obvious strategy to increase the Ni-S-Ni angles is the use of a large coligand L'. [18] Another strategy to widen the angles could be the attachment of dihalogen molecules to the thiophenolate residues in the form of thiophenolate-dihalogen CT (charge transfer) interactions, as suggested recently by the structure of the Br2 adduct of complex [Ni2L 1 (-OAc)] + 1. [33] Thus, upon CT complex formation the average Ni-S-Ni angles increase significantly from 89.6° in 1 to 93.4° in 1·Br2.…”

Section: Introductionmentioning

confidence: 99%

Interplay of Magnetic Exchange Interactions and NiSNi Bond Angles in Polynuclear Nickel(II) Complexes

Krupskaya¹,

Alfonsov²,

Parameswaran³

et al. 2010

ChemPhysChem

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The ability of bridging thiophenolate groups (RS -) to transmit magnetic exchange interactions between paramagnetic Ni(II) ions has been examined. Specific attention was paid to complexes with large Ni-SR-Ni angles. For this purpose, dinuclear [Ni2Land trinuclear [Ni3L 2 (OAc)2][BPh4]2 (3), where H2L 1 and H2L 2 represent 24-membered macrocyclic amino-thiophenol ligands, were prepared and fully characterized by IR-and UV-vis spectroscopy, X-ray crystallography, static magnetization M measurements and high-field electron spin resonance (HF-ESR). The dinuclear complex 2 has a central N3Ni2(-S)2(-OAc)Ni2N3 core with a mean Ni-S-Ni angle of 92°. The macrocycle L 2 supports a trinuclear complex 3, with distorted octahedral N2O2S2 and N2O3S coordination environments for one central and two terminal Ni(II) ions, respectively. The Ni-S-Ni angles are at 132.8° and 133.5°. We find that the variation of the bond angles has a very strong impact on the magnetic properties of the Ni complexes. In the case of the Ni2-complex, temperature T and magnetic field B dependencies of M reveal a ferromagnetic coupling J = -29 cm -1 between two Ni(II) ions (H = JS1S2). HF-ESR measurements yield a negative axial magnetic anisotropy (D < 0) which implies a bistable (easy axis) magnetic ground state. In contrast, for the Ni3-complex we find an appreciable antiferromagnetic coupling J' = 97 cm -1 between the Ni(II) ions and a positive axial magnetic anisotropy (D > 0) which implies an easy plane situation.

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Realization of Unusual Ligand Binding Motifs in Metalated Container Molecules: Synthesis, Structures, and Magnetic Properties of the Complexes [(L^Me)Ni₂(μ‐L′)]ⁿ⁺ with L′=NO₃⁻, NO₂⁻, N₃⁻, N₂H₄, Pyridazine, Phthalazine, Pyrazolate, and Benzoate

Cited by 70 publications

References 114 publications

Hysteretic Magnetic Bistability Based on a Molecular Azide Switch

Hysteretic Magnetic Bistability Based on a Molecular Azide Switch

Dinuclear Complexes as Building Blocks for Tetra-Nuclear Macrocyclic Complexes with Dithiolate Macrocyclic Ligand

Interplay of Magnetic Exchange Interactions and NiSNi Bond Angles in Polynuclear Nickel(II) Complexes

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