Thermally Induced Single-Crystal-to-Single-Crystal Transformation and Heterogeneous Catalysts for Epoxidation Reaction of Co(II) Based Metal–Organic Frameworks Containing 1,4-Phenylenediacetic Acid

Four new metal–organic frameworks (MOFs) based on 1,4-phenylenediacetic acid (1,4-H₂phda), [Co­(1,4-phda)­(4,4′-bpa)] (<b>1</b>), [Co­(1,4-phda)­(4,4′-bpp)] (<b>2</b>), [Co­(1,4-phda)­(4,4′-bpa)­(H₂O)₂] (<b>3</b>), and [Co­(1,4-phda)­(4,4′-bpa)] (<b>3a</b>) (4,4′-bpa = 1,2-bis­(4-pyridyl)­ethane and 4,4′-bpp = 1,3-bis­(4-pyridyl)­propane) were successfully synthesized. The various synthetic methods play an important role in the formation of diverse structural frameworks. Compound <b>1</b> shows a 3D framework, while <b>2</b>, <b>3</b>, and <b>3a</b> exhibit 2D layered MOFs with different architectures. The irreversible thermally induced single-crystal-to-single-crystal transformation with chromotropism from <b>3</b> to <b>3a</b> was observed, which was established by the breakage and reformation of coordination bonds around Co­(II) centers. The orientation of coordinated 4,4′-bpa ligand and conformation of 1,4-phda ligand play a key role on pore opening in <b>3</b> and pore closing in <b>3a</b>. Furthermore, the functional properties as heterogeneous catalysts of these MOFs including epoxidation of alkenes and photocatalytic performance for MB degradation have been investigated. The heterogeneous catalytic properties of <b>1</b>, <b>2</b>, and <b>3a</b> exhibit high catalytic activity with good catalyst stability

Hypoxylonone, a new oxa-bridged seven-membered ring analog from fungus <i>Hypoxylon</i> cf. <i>subgilvum</i> SWUF15-004

A new oxa-bridged seven-membered ring analog, hypoxylonone (1), and thirteen known compounds (2–14) were isolated from fungus Hypoxylon cf. subgilvum SWUF15-004. The structures were elucidated by the analysis of spectroscopic (IR, 1 D and 2 D NMR), HRESIMS and X-ray diffraction (MoKα) data. Several isolated compounds were evaluated for cytotoxicity against four human cancer cell lines (HeLa, HT29, MCF-7, A549). Compound 1 exhibited weak inhibitory effects of the nitric oxide production in RAW264.7 cells. Compounds 8 and 9 exhibited slight cytotoxicity.</p

A Series of Cyanoacetato Copper(II) Coordination Polymers with Various <i>N</i>,<i>N</i>′‑Ditopic Spacers: Structural Diversity, Supramolecular Robustness, and Magnetic Properties

Five novel copper­(II) coordination polymers containing cyanoacetate (cna) anion with various <i>N</i>,<i>N</i>′-ditopic spacers [Cu­(cna)₂­(pyz)]_<i>n</i> (<b>1</b>), [Cu­(cna)₂­(bpy)­(H₂O)₂]_<i>n</i> (<b>2</b>), [Cu­(cna)₂­(dpe)]_<i>n</i> (<b>3</b>), [Cu­(cna)₂­(dpe)]_<i>n</i>­(H₂O)_<i>n</i> (<b>4</b>), and [Cu­(cna)₂­(bpa)]_<i>n</i> (<b>5</b>) (when pyz = pyrazine, bpy = 4,4′-bipyridyl, dpe = 1,2-di­(4-pyridyl)­ethylene, and bpa = 1,2-di­(4-pyridyl)­ethane) were structurally and spectroscopically characterized. Compound <b>1</b> shows a two-dimensional (2D) sheet structure constructed from μ₂-1,3­(<i>syn,anti</i>) coordinative mode of cyanoacetate and μ₂-pyz linking adjacent Cu­(II) centers. Compound <b>2</b> exhibits a one-dimensional (1D) polymeric chain which is formed by μ₂-bpy bridging between [Cu­(cna)₂­(H₂O)₂] units, whereas compounds <b>3</b>–<b>5</b> reveal 1D ladder-like structures which are built from double-μ₂-dpe/bpa spacers connecting neighboring Cu­(II) cyanoacetate dimers. Weak interactions such as hydrogen bonding and N<i>···π</i> and/or C–H<i>···π</i> interactions join the adjacent layers of <b>1</b> or polymeric chains of <b>2</b>–<b>5</b> to stabilize overall supramolecular networks. The thermal stabilities of <b>1</b>–<b>5</b> were investigated. Interestingly, compound <b>2</b> reveals a robust supramolecular framework constructed by 1D polymeric chains during thermal dehydration and rehydration processes, which has been further verified by spectroscopic techniques, elemental analyses, thermogravimetric analysis, and X-ray powder diffraction. Moreover, this behavior is not observed in the isomorphous series containing Co­(II) and Ni­(II) ions. The magnetic properties of <b>1</b> and <b>3</b> exhibit very weak antiferromagnetic interactions between Cu­(II) centers

New Series of Triply Bridged Dinuclear Cu(II) Compounds: Synthesis, Crystal Structure, Magnetic Properties, and Theoretical Study

Five new triply bridged dinuclear Cu(II) compounds have been synthesized, and their magnetic properties have been measured and characterized. The magnetic coupling constants (<i>J</i>) of these compounds plus a previously structurally characterized compound of the same type have been derived by appropriate fitting of the experimentally measured molar susceptibility variation with the temperature. Two of the compounds are ferromagnetically coupled, and three are antiferromagnetically coupled with <i>J</i> values in the [+150, −40] cm^–1 range. The validity of the structural aggregate Addison’s parameter as a qualitative magneto-structural correlation is confirmed. The origin of the magnetic interactions and the magnitude of the magnetic coupling have been analyzed by means of density functional theory-based calculations using a variety of state of the art exchange-correlation potentials. It is shown that the long-range separated LC-ωPBE provides the overall best agreement with experiment for this family as well as for a set of previously reported hetero triply bridged dinuclear Cu(II) compounds, especially for ferromagnetic systems

Drastic Effect of Lattice Propionitrile Molecules on the Spin-Transition Temperature of a 2,2′-Dipyridylamino/s-triazine-Based Iron(II) Complex

Reaction of iron­(II) selenocyanate (obtained from Fe­(ClO₄)₂ and KNCSe) with 2-(<i>N</i>,<i>N</i>-bis­(2-pyridyl)­amino)-4,6-bis­(pentafluorophenoxy)-(1,3,5)­triazine (<b>L1</b>^<b>F</b>) in propionitrile produces the compound [Fe­(<b>L1</b>^<b>F</b>)₂(NCSe)₂]·2CH₃CH₂CN (<b>1</b>^<b>NCSe</b><b>·2PrCN</b>), which shows spin-crossover (SCO) properties characterized by a <i>T</i>_1/2 of 283 K and a Δ<i>T</i>₈₀ (i.e., temperature range within which 80% of the transition considered occurs) of about 65 K. Upon air exposure, <b>1</b>^<b>NCSe</b><b>·2PrCN</b> gradually converts to a new SCO species that exhibits different properties, as reflected by <i>T</i>_1/2 = 220 K and Δ<i>T</i>₈₀ = 70 K. Various characterization techniques, namely, IR spectroscopy, thermogravimetric analysis, and thermodiffractometric studies, reveal that the new phase is obtained through the loss of the lattice propionitrile molecules within several days upon air exposure or several hours upon heating above 390 K