A Polyoxometalate–Cyanometalate Multilayered Coordination Network

The reaction of the ε-Keggin polyoxometalate (POM) [PMo₁₂O₃₆(OH)₄{La­(H₂O)₄}₄]⁵⁺ with Fe^II(CN)₆^4– under typical bench conditions at room temperature and ambient pressure has afforded the novel [ε-PMo₁₂O₃₇(OH)₃{La­(H₂O)₅(Fe­(CN)₆)_0.25}₄] network, which exhibits a three-dimensional multilayered structure. The compound has been fully characterized by synchrotron-radiation X-ray crystallography, IR spectroscopy, elemental analysis, and thermogravimetric analysis. This coordination network constitutes the first example of a cyanometalate bonded to a POM unit

High Thermal Durability of Water-Free Copper-Octacyanotungsten-Based Magnets Containing Halogen Bonds

Two-dimensional (2-D) cyano-bridged Cu–W bimetallic assemblies that include halogen-substituted pyridine molecules, [Cu^II(3-iodopyridine)₄][Cu^II(3-iodopyridine)₂]₂[W^V(CN)₈]₂ (<b>1</b>) (triclinic crystal structure, <i>P</i>1̅ space group), [Cu^II(3-bromopyridine)₄][Cu^II(3-bromopyridine)₂]₂[W^V(CN)₈]₂ (<b>2</b>) (triclinic, <i>P</i>1̅), and [Cu^II(3-chloropyridine)₂(H₂O)₂][Cu^II(3-chloropyridine)₂]₂[W^V(CN)₈]₂·4H₂O (<b>3</b>) (monoclinic, <i>P</i>2₁/<i>c</i>), were synthesized. Thermogravimetric measurements demonstrate that <b>1</b> and <b>2</b> have high thermal durability up to ca. 150 °C (423 K) due to the lack of water molecules in the crystal and the stacked Cu–W 2-D layers with halogen bonding between halogen-substituted pyridine and the cyano nitrogen of octacyanotungstate. In contrast, <b>3</b> exhibits weight loss above ca. 50 °C (323 K) as the water molecules between the 2-D layers are removed upon heating. Magnetic measurements show that <b>1</b>–<b>3</b> are ferromagnets due to parallel ordering of the magnetic spins on Cu^II (<i>S</i> = 1/2) and W^V (<i>S</i> = 1/2) with Curie temperatures (<i>T</i>_C) of 4.7 K (<b>1</b>), 5.2 K (<b>2</b>), and 7.2 K (<b>3</b>)

Green to Red Luminescence Switchable by Excitation Light in Cyanido-Bridged Tb^III–W^V Ferromagnet

Green to Red Luminescence Switchable by Excitation Light in Cyanido-Bridged Tb^III–W^V Ferromagne

Chiral Ln^III(tetramethylurea)–[W^V(CN)₈] Coordination Chains Showing Slow Magnetic Relaxation

We prepared a series of isostructural chiral cyanido-bridged zigzag chains [Ln­(tmu)₅]­[W­(CN)₈] (Ln = Gd, <b>1</b>; Tb, <b>2</b>; Dy, <b>3</b>; Ho, <b>4</b>; Er, <b>5</b>; Tm, <b>6</b>) using achiral tmu = tetramethylurea. Their chiral character was confirmed with single crystal X-ray diffraction and circular dichroism measurements. Magnetic studies show antiferromagnetic interactions within cyanido-bridged Ln^III–W^V pairs, and interchain ordering of net spins in <b>1</b>, <b>4</b>, and <b>5</b>. It is worth to emphasize that Dy-, Er-, and Tm-based systems combine magnetic field-induced slow magnetic relaxation and chirality. Analysis of AC magnetic data with two relaxation processes for <b>5</b> gives energy barrier Δ_τ/<i>k</i>_B = 1.2(3) K and relaxation time τ₀ = 2.63(8) × 10^–2 s, and Δ_τ/<i>k</i>_B = 22(2) K and τ₀ = 1.21(3) × 10^–8 s. Cole–Cole function fits for <b>3</b> and <b>6</b> result in Δ_τ/<i>k</i>_B = 17(1) K, τ₀ = 1.68(3) × 10^–6 s and Δ_τ/<i>k</i>_B = 5.7(3) K, τ₀ = 1.53(4) × 10^–2 s, respectively. Slower relaxation processes have been assigned to dipole–dipole interactions while faster ones to single ion magnet behavior of Ln­(III) ions

Supramolecular Two-Dimensional Network Mediated via Sulfur’s σ‑Holes in a Conducting Molecular Crystal: Effects of Its Rigidity on Physical Properties and Structural Transition

This study reveals that noncovalent intermolecular interactions mediated by σ-holes on sulfur atoms can function as an efficient tool to design and construct a novel supramolecular motif, and that these noncovalent bonds are rigid enough to regulate the displacement of molecules at the structural transition. A novel two-dimensional cation···anion supramolecular structure via sulfur’s σ-holes was constructed in a functional molecular crystal, (ethyl-4-bromothiazolium)₂[Pt­(mnt)₂]₃ (mnt = maleonitriledithiolato). The unit cell contained two crystallographically independent anions <b>A</b> and <b>B</b>. Electrostatic σ-hole bonds were detected between σ-holes on sulfur in the cation and lone pairs of −CN moieties in <b>B</b>, while <b>A</b> did not form such S···N σ-hole bonds. This salt exhibited a structural transition at ca. 150 K, in which <b>B</b> did not show apparent displacement, while <b>A</b> shifted along the anion’s stacking direction. This shift enhanced trimerization of the anion in the low-temperature phase, leading to the enhanced antiferromagnetic exchange interaction and the increased activation energy in the electrical conduction. We showed that sulfur-based σ-hole bonds are rigid enough to contribute to modulating the physical properties through regulating the displacement of molecules in molecular materials

Synthesis and Characterization of B‑Heterocyclic π‑Radical and Its Reactivity as a Boryl Radical

The first isolation and full characterization of the stable, persistent diazaboracyclic neutral radical <b>3</b> is reported. Reduction of base-stabilized difluororoborane <b>2</b> provided radical <b>3</b> as a neutral molecule having a planar sp² boron atom attached to one fluorine and two nitrogen atoms. ESR spectroscopy and DFT calculations indicated that the unpaired electron is delocalized over the six-membered ring. Because of an electronic transition related to the singly occupied molecular orbital, <b>3</b> has a characteristic red color, as UV–vis spectroscopy showed an absorption maximum at 498 nm. Although DFT calculations suggested that radical <b>3</b> has relatively low spin density on the boron atom in comparison with the nitrogen and carbon atoms in the six-membered ring, <b>3</b> reacted as a base-stabilized boryl radical when treated with benzoquinone or benzoyl peroxide

Cesium Cyano-Bridged Co^II–M^V (M = Mo and W) Layered Frameworks Exhibiting High Thermal Durability and Metamagnetism

Two-dimensional cesium bimetal cyano-bridged assemblies Cs^I₄Co^II[Mo^V(CN)₈]­Cl₃ (<b>CsCoMo</b>) and Cs^I₄Co^II[W^V(CN)₈]­Cl₃ (<b>CsCoW</b>) were synthesized. The negatively charged and solvent-free {Co^II[M^V(CN)₈]­Cl₃}^4– (M = Mo, W) coordination layers are separated by Cs⁺ ions. Themogravimetric measurements show that these compounds reveal high thermal durability up to 523 K (250 °C), which is due to the absence of solvent molecules in their crystal structures. The magnetic measurements show that <b>CsCoMo</b> and <b>CsCoW</b> are metamagnets showing the field-induced transition from an antiferromagnetic phase with Néel temperature of 25 K to a ferromagnetic phase, which is observed at high critical magnetic field of 24 kOe at 1.8 K. These originate from antiferromagnetic interactions between ferromagnetically coupled cyano-bridged Co^II–M^V layers, and the contribution from single-ion anisotropy of Co^II

Conjunction of Chirality and Slow Magnetic Relaxation in the Supramolecular Network Constructed of Crossed Cyano-Bridged Co^II–W^V Molecular Chains

The addition of chiral 2,2′-(2,6-pyridinediyl)­bis­(4-isopropyl-2-oxazoline) (<i>i</i>Pr-Pybox) to a self-assembled Co^II–[W^V(CN)₈] magnetic system gives two enantiomorphic cyano-bridged chains, {[Co^II((<i>S</i>,<i>S</i>)-<i>i</i>Pr-Pybox)­(MeOH)]₃[W^V(CN)₈]₂·​5.5MeOH·​0.5H₂O}_<i>n</i> (<b>1</b>-<i>SS</i>) and {[Co^II((<i>R</i>,<i>R</i>)-<i>i</i>Pr-Pybox) (MeOH)]₃[W^V(CN)₈]₂·​5.5MeOH·​0.5H₂O}_<i>n</i> (<b>1</b>-<i>RR</i>). Both compounds crystallize with a structure containing a unique crossed arrangement of one-dimensional chains that form a microporous supramolecular network with large channels (14.9 Å × 15.1 Å × 15.3 Å) filled with methanol. The investigated materials exhibited optical chirality, as confirmed by natural circular dichroism and UV–vis absorption spectra. <b>1</b>-(<i>SS</i>) and <b>1</b>-(<i>RR</i>) are paramagnets with cyano-mediated Co^II–W^V magnetic couplings that lead to a specific spin arrangement with half of the W^V ions coupled ferromagnetically with their Co^II neighbors and the other half coupled antiferromagnetically. Significant magnetic anisotropy with the easy axis along the [101] direction was confirmed by single-crystal magnetic studies and can be explained by the single-ion anisotropy of elongated octahedral Co^II sites. Below 3 K, the frequency-dependent χ_M^″(<i>T</i>) signal indicated slow magnetic relaxation characteristic of single-chain magnets

Synthesis and Characterization of B‑Heterocyclic π‑Radical and Its Reactivity as a Boryl Radical

The first isolation and full characterization of the stable, persistent diazaboracyclic neutral radical <b>3</b> is reported. Reduction of base-stabilized difluororoborane <b>2</b> provided radical <b>3</b> as a neutral molecule having a planar sp² boron atom attached to one fluorine and two nitrogen atoms. ESR spectroscopy and DFT calculations indicated that the unpaired electron is delocalized over the six-membered ring. Because of an electronic transition related to the singly occupied molecular orbital, <b>3</b> has a characteristic red color, as UV–vis spectroscopy showed an absorption maximum at 498 nm. Although DFT calculations suggested that radical <b>3</b> has relatively low spin density on the boron atom in comparison with the nitrogen and carbon atoms in the six-membered ring, <b>3</b> reacted as a base-stabilized boryl radical when treated with benzoquinone or benzoyl peroxide