6 research outputs found
Size-Controlled Hapticity Switching in Sandwiches
Sandwich complexes of lanthanides have recently attracted a considerable amount of interest due to their applications as Single Molecule Magnet (SMM). Herein, a comprehensive series of heteroleptic lanthanide sandwich complexes ligated by the cyclononatetraenyl (Cnt) and the cyclooctatetraenyl (Cot) ligand [Ln(Cot)(Cnt)] (Ln=Tb, Dy, Er, Ho, Yb, and Lu) is reported. The coordination behavior of the Cnt ligand has been investigated along the series and shows different coordination patterns in the solid-state depending on the size of the corresponding lanthanide ion without altering its overall anisotropy. Besides the characterization in the solid state by single-crystal X-ray diffraction and in solution by NMR, static magnetic studies and ab initio computational studies were performed
Cyclic Structural Transformations from Crystalline to Crystalline to Amorphous Phases and Magnetic Properties of a Mn(II)-Based Metal–Organic Framework
A three-dimensional
MnÂ(II) framework, [Mn<sub>2</sub>(H<sub>2</sub>L)Â(L)<sub>0.5</sub>Â(MeOH)Â(DEF)]·0.1MeOH·0.1DEF·1.4H<sub>2</sub>O (<b>1</b>; H<sub>4</sub>L = 2,3-dioxido-1,4-benzenedicarboxylic
acid), was synthesized under solvothermal conditions in diethylformamide/methanol
(DEF/MeOH), where the Mn centers adopt octahedral and unusual pentagonal
bipyramidal geometries. The ligand H<sub>4</sub>L was subject to deprotonation
to create μ<sub>4</sub>-H<sub>2</sub>L<sup>2–</sup> and
μ<sub>6</sub>-L<sup>4–</sup> anionic bridges, leading
to the construction of a coordination network. The MeOH exchange process
of crystalline <b>1</b> allowed for another crystalline phase
(<b>1a</b>), which reversibly returned to the original crystalline
state upon resolvation in DEF/MeOH. After evacuation of <b>1a</b>, the amorphous phase <b>1b</b> was irreversibly formed, followed
by the restoration of the original phase <b>1</b> upon resolvation
in DEF/MeOH. Consequently, this framework underwent cyclic structural
transformations from the crystalline (<b>1</b>) to crystalline
(<b>1a</b>) to amorphous (<b>1b</b>) and back to crystalline
(<b>1</b>) phase, which are unique transformations for soft
coordination networks. Magnetic measurements demonstrated that antiferromagnetic
interactions were operative between the MnÂ(II) ions and were effectively
mediated by the oxygen moieties of the μ<sub>6</sub>-L<sup>4–</sup> bridge
Control of Interchain Antiferromagnetic Coupling in Porous Co(II)-Based Metal–Organic Frameworks by Tuning the Aromatic Linker Length: How Far Does Magnetic Interaction Propagate?
Three
MOF-74-type CoÂ(II) frameworks with one-dimensional hexagonal channels
have been prepared. CoÂ(II) spins in a chain are ferromagnetically
coupled through carboxylate and phenoxide bridges. Interchain antiferromagnetic
couplings via aromatic ring pathways operate over a Co–Co length
shorter than ∼10.9 Å, resulting in a field-induced metamagnetic
transition, while being absent over lengths longer than ∼14.7
Ã…