Manganese carboxylate clusters: from structuralaesthetics to single-molecule magnets

Arom, Guillem; Aubin, Sheila M. J.; Bolcar, Milissa A.; Christou, George; Eppley, Hilary J.; Folting, Kirsten; Hendrickson, David N.; Huffman, John C.; Squire, Rachel C.; Tsai, Hui-Lien; Wang, Sheyi; Wemple, Michael W.

doi:10.1016/s0277-5387(98)00104-1

Cited by 193 publications

(128 citation statements)

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“…An example should explain. Nickel(II) has a configuration 3d 8 . A compound with four ligands can have either a tetrahedral or square planar coordination geometry.…”

Section: A Nano History Of Molecular Magnetismmentioning

confidence: 99%

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Lanthanides in the frame of Molecular Magnetism

Gatteschi

2014

EPJ Web of Conferences

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Abstract. Molecular magnetism is producing new types of materials which cover up to date aspects of basic science together with possible applications. This article highlights recent results from the point of view of lanthanides which are now intensively used to produce single molecule magnets, single chain and single ion magnets. After a short introduction reminding the main steps of development of molecular magnetism, the basic properties of lanthanides will be covered highlighting important features which are enhanced by the electronic structure of lanthanides, like spin frustration and chirality, anisotropy and non collinear axes in zero and one dimensional materials. A paragraph of conclusions will discuss what has been done and theperspectives to be expected. A Nano history of molecular magnetismMolecular magnetism is a relatively recent section of magnetism which evolved from magnetochemistry. Magnetochemistry is the use of magnetic measurements in order to obtain structural information. An example should explain. Nickel(II) has a configuration 3d 8 . A compound with four ligands can have either a tetrahedral or square planar coordination geometry. A ligand field description shows that the five degenerate d orbitals in cubic symmetry remove their degeneracy due to low symmetry effects. The tetrahedral field is weaker than the square planar and the latter forces the electron spins to pair, while the weak tetrahedral keeps two electrons unpaired. A simple magnetic measurement at room temperature decides about the coordination structure. In fact the tetrahedral nickel (II) complexes are paramagnetic and square planar are diamagnetic. A useful technique but nothing more.The change occurred from the 60s of last century when it was realized that molecular chemistry could yield new types of magnetic materials, following the same type of evolution which took place on conductors where the introduction of molecular techniques determined a technological breakthrough.The goal at the beginning was to design and synthesize high T organic ferromagnets, but the challenge appeared soon to be too difficult and in order to start from a less hard field the goal was broadened rapidly to molecular ferromagnets i.e. to materials which may contain metal ions together with organic molecules. The results were promising, teaching how to develop strategies to design and synthesize ferro-or ferri-magnetic coupled molecules. The result was the production of low dimensional magnets while 3D materials were more difficult and the number of molecular magnets working at room temperature did not exceed 2 [1-4]. The critical temperatures of pure organic ferromagnets are still in the 30 K range.Luckily in those years there was a keen interest among physicists towards low D magnets and the exotic molecular magnets attracted the interest of quite a few. The problem was the different languages of the two communities. Physicists for instance needed one-dimensional antiferro-magnets with S> ½ to test the Haldane theory, and the only systems they we...

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“…An example should explain. Nickel(II) has a configuration 3d 8 . A compound with four ligands can have either a tetrahedral or square planar coordination geometry.…”

Section: A Nano History Of Molecular Magnetismmentioning

confidence: 99%

“…SMM was the catchy name invented [8] to define materials whose magnetization below a blocking temperature behaves like that of a magnet, including hysteresis. The behavior is similar to that of a superparamagnet the height of the barrier being of molecular origin.…”

Section: A Nano History Of Molecular Magnetismmentioning

confidence: 99%

Lanthanides in the frame of Molecular Magnetism

Gatteschi

2014

EPJ Web of Conferences

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Section: Abstract: Ligand Design / O Ligands / Nmr Spectroscopy / Magmentioning

confidence: 99%

“…[4,5] A very successful approach for accessing such species has been the assembly of metal ions by means of small bridging ligands, such as carboxylates, where growth into infinite arrays is often prevented by additional terminal ligands. [6,7] Such a method has been sometimes termed "serendipitous approach" since it does not allow prediction of the structure of the final species.[8] An alternative strategy has been the design and preparation of complicated multidentate ligands favoring the assembly of metal ions into aggregates with topologies that may be anticipated from the structure of these ligands. This second course of action has led to the production of a large amount of polynuclear edifices displaying sophisticated shapes and architectures, such as helicates, [9] grids, [10] cylinders, [11] catenates, [12] and many more.…”

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A Zig‐Zag [Mn^II₄] Cluster from a Novel Bis(β‐diketonate) Ligand

et al. 2006

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Keywords: Ligand design / O ligands / NMR spectroscopy / Magnetism / MnA new ligand, H 5 L3, has been synthesized featuring seven linearly arranged oxygen donors in form of two 1,3-diketone and three phenol groups. The X-ray structure of H 5 L3 unveils a rare case where one of the diketones is in the enolic form and the other one in the bis(carbonyl) form. This structure is shown by 1 H NMR to persist in solution. Reaction of H 5 L3 with Mn(AcO) 2 in pyridine leads to the novel tetranuclear cluster [Mn 4 (H 2 L3) 2 (OAc) 2 (py) 5 ] (1), which displays an un-The preparation of molecular cluster complexes of interacting transition-metal ions is useful to areas as important and diverse as molecular magnetism, [1,2] homogeneous catalysis [3] or bioinorganic chemistry. [4,5] A very successful approach for accessing such species has been the assembly of metal ions by means of small bridging ligands, such as carboxylates, where growth into infinite arrays is often prevented by additional terminal ligands. [6,7] Such a method has been sometimes termed "serendipitous approach" since it does not allow prediction of the structure of the final species.[8] An alternative strategy has been the design and preparation of complicated multidentate ligands favoring the assembly of metal ions into aggregates with topologies that may be anticipated from the structure of these ligands. This second course of action has led to the production of a large amount of polynuclear edifices displaying sophisticated shapes and architectures, such as helicates, [9] grids, [10] cylinders, [11] catenates, [12] and many more. Of these molecular species, only a minority have the metal ions disposed in close proximity so as to show cooperative effects resulting from strong magnetic-exchange interactions [13] or metalmetal bonding.[ Scheme 1), [15,16] aimed at forming molecular strings of metal ions in close proximity. Maximum occupancy of their coordination pockets would result in tetranuclear clusters in form of [M 4 ] chains [17] for H 3 L1 and aligned [M 2 ] 2 dimers of dimers for H 4 L2. Reactions of the latter with M(OAc) 2 salts have resulted invariably in the formation of complexes of the type [M 2 (H 2 L2) 2 (S) n ] (n = 2 or 4; S = solvent; M = Mn, Ni, Co, Cu).[16] Similar dinuclear compounds have been obtained with H 3 L1.[18] However, in the absence of a coordinating solvent, molecules exhibiting higher occupancy, [Co 3 (HL1) 3 ] and [Mn 3 (HL1) 3 ], were characterized, which represented a new asymmetric topology within the context of coordination helicates. [19] Inspired by these early results, we have now designed and synthesized a new ligand displaying as many as six adjacent coordination pockets (H 5 L3, Scheme 1). Reaction of H 5 L3 with Mn II produces a very rare magnetically exchanged tetranuclear complex featuring an [Mn 4 O 6 ] core in form of a zig-zag chain.The new ligand H 5 L3 {2-hydroxy-1,3-bis[3-(2-hydroxyphenyl)-3-oxopropionyl]benzene} was prepared from the methoxide derivative H 4 L4 (Scheme 1).[20] The latter is also a n...

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“…1 Since the dodecanulear manganese cluster with the composition [Mn12O12(O2CMe)16-(H2O)4] (Mn12ac) had been discovered as an singlemolecule magnet, 2,3 many efforts have been made to achieve larger cluster compounds showing SMM behaviors. 4 Especially, manganese carboxylate cluster chemistry has proved to be a rich source of a variety of polynuclear species. 5,6 Specific examples of SMMs except Mn12ac include the tetranuclear cubane [Mn IV Mn III 3O3X] 6+ core 7 and [Fe4(sae)4-(MeOH)4] (sae = 2-salicylidene-amino-1-ethanol), 8 the octanuclear Fe(III) cluster [Fe8O2(OH)12(tacn) 6] 8+ (tacn = tetraazacyclononane), 9 and the tetranuclear butterfly complex [V4O2(O2CR)7(L)2]n+ (L=bipyridine or picolinate).…”

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confidence: 99%