Synthesis, structural studies and vibrational spectroscopy of Fe2+ and Zn2+ complexes containing 4,4′-bipyridine and barbiturate anion

An organic-organometallic CO-releasing material comprising 4,4'-bipyridine and molybdenum subcarbonyl building blocks

Over the past two decades, following the discovery of the important biological roles of carbon monoxide (CO), metal carbonyl complexes have been intensively studied as CO-releasing molecules (CORMs) for therapeutic applications. To improve the properties of "bare" low molecular weight CORMs, attention has been drawn to conjugating CORMs with macromolecular and inorganic scaffolds to produce CO-releasing materials (CORMAs) capable of storing and delivering large payloads of the gasotransmitter. A significant obstacle is to obtain CORMAs that retain the beneficial features of the parent CORMs. In the present work, a crystalline metal-organic framework (MOF) formulated as Mo(CO)3(4,4'-bipyridine)3/2 (Mobpy), with a structure based on Mo(CO)3 metallic nodes and bipyridine linkers, has been prepared in near quantitative yield by a straightforward reflux method, and found to exhibit CO-release properties that mimic those typically observed for molybdenum carbonyl CORMs. Mobpy was characterized by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), FT-IR, FT-Raman and diffuse reflectance (DR) UV-vis spectroscopies, and 13C{1H} cross-polarization (CP) magic-angle spinning (MAS) NMR. The release of CO from Mobpy was studied by the deoxy-myoglobin (deoxy-Mb)/carbonmonoxy-myoglobin (MbCO) UV-vis assay. Mobpy liberates CO upon contact with a physiological buffer in the dark, leading to a maximum released amount of 1.3-1.5 mmol g-1, after 1.5 h at 37 °C, with half-lives of 0.5-1.0 h (time to transfer 0.5 equiv. of CO to Mb). In the solid-state and under open air, Mobpy undergoes complete decarbonylation over a period of 42 days, corresponding to a theoretical CO-release of 7.25 mmol g-1.

Neutral and Cationic Chelidonate Coordination Polymers with N,N′-Bridging Ligands

The biomolecule chelidonic acid (H2chel, 4-oxo-4H-pyran-2,6-dicarboxylic acid) has been used to build new coordination polymers with the bridging N,N′-ligands 4,4′-bipyridine (4,4-bipy) and 1,2-bis(4-pyridyl)ethane (bpe). Four compounds have been obtained as single crystals: 1D cationic coordination polymers [M(4,4-bipy)(OH2)4]2+ with chelidonate anions and water molecules in the second coordination sphere in 1∞[Zn(4,4-bipy)(H2O)4]chel·3H2O (2) and in the two pseudopolymorphic 1∞[Cu(4,4-bipy)(H2O)4]chel·nH2O (n = 3, 4a; n = 6, 4b), and the 2D neutral coordination polymers 2∞[Zn(chel)(4,4-bipy)(H2O)]·2H2O (1) and 2∞[Zn(chel)(bpe)(H2O)]·H2O (3) where the chelidonate anion acts as a bridging ligand. The effects of the hydrogen bonds on the crystal packing were analyzed. The role of the water molecules hosted within the crystals lattices was also studied.

Raman spectroscopy studies of the terahertz vibrational modes of a DUT-8 (Ni) metal–organic framework

Raman spectroscopy and Molecular Dynamic simulations were applied to study low-frequency vibrations of a flexible metal–organic framework DUT-8(Ni).

Versatile structures of group 13 metal halide complexes with 4,4′-bipy: from 1D coordination polymers to 2D and 3D metal–organic frameworks

The nature of the group 13 metal halides strongly affects the structure of their complexes with 4,4′-bipy.

MOF crystal growth: UV resonance Raman investigation of metal–ligand binding in solution and accelerated crystal growth methods

Resonance Raman spectroscopy can detect metal–ligand binding in solution during the formation of MOF crystals.

Rubidium 2,4,6-trioxo-1,3-diazinan-5-ide-1,3-diazinane-2,4,6-trione-water (1/1/1)

The asymmetric unit of the title compound, Rb⁺·C₄H₃N₂O₃⁻·C₄H₄N₂O₃·H₂O, consists of one rubidium cation, a barbituric acid mol­ecule, a barbiturate anion and one water mol­ecule. The rubidium ion has seven close-contact inter­actions with O atoms, with Rb⋯O distances ranging from 2.8594 (16) to 3.2641 (14) Å. These seven O atoms together with an eighth O atom at 3.492 (2) Å away from Rb form a distorted polyhedron with shape inter­mediate between an anti­prism and a dodeca­hedron. The Rb⁺ ions connect layers built of organic components and water mol­ecules linked via N—H⋯O and O—H⋯O hydrogen bonds.