SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Inorganic chemistry

28

Nanoscopic uranyl coordination cages have been prepared by a facile route involving self-assembly via temperature and solvent-driven, in situ ligand synthesis. The synthesis of hydrogen arsenate and pyroarsonate ligands in situ enhances flexibility, which is an important factor in producing these compounds.

Concepts: Ammonia, Chemical reaction, Coordination complex, Ligand, Carbon monoxide, Inorganic chemistry, In situ, Coordination number

28

This tutorial review discusses the structural and electronic consequences of the Jahn-Teller effect in transition metal complexes, focussing on copper(ii) compounds which tend to be the most studied. The nature of a Jahn-Teller distortion in molecular complexes and extended lattices can be manipulated by application of pressure or temperature, by doping a molecule into a host lattice, or simply by molecular design. Many of these results have been achieved using compounds with a trans-[CuX(4)Y(2)] coordination sphere, which seems to afford copper centres that are particularly sensitive to their environment. Jahn-Teller distortions lead to some unusual phenomena in molecular magnetism, and are important to the functionality of important classes of conducting and superconducting ceramics.

Concepts: Electron, Oxygen, Chemical bonding, Zinc, Coordination chemistry, Inorganic chemistry, Silver, Jahn–Teller effect

28

The complexation of Cm(iii) and Eu(iii) with 2,6-bis(5,6-di(sulfophenyl)-1,2,4-triazin-3-yl)pyridine (aq-BTP) is studied in water at pH 3.0 applying time-resolved laser fluorescence spectroscopy. With increasing ligand concentration [M(H(2)O)(9-3n)(aq-BTP)(n)] (M = Cm(iii)/Eu(iii), n = 1, 2, 3) complex species are spectroscopically identified. The conditional stability constants of the M(iii) 1 : 3 complex species with aq-BTP are log β(03) = 12.2 for Cm(iii) and log β(03) = 10.2 for Eu(iii). The complexation reaction is enthalpy- and entropy-driven for both metal ions, while the enthalpy change ΔH(03) is 9.7 kJ mol(-1) more negative for Cm(iii); changes in ΔS(03) are marginal. The difference in ΔG(03) of -12.7 kJ mol(-1) between the formation of the [M(aq-BTP)(3)] complexes agrees with aq-BTP’s selectivity in liquid-liquid extraction studies.

Concepts: Spectroscopy, Ligand, Lone pair, Coordination chemistry, Inorganic chemistry, Enthalpy, Logarithm, Standard enthalpy change of formation

27

Ion conduction and transport in solids are both interesting and useful and are found in widely distinct materials, from those in battery-related technologies to those in biological systems. Scientists have approached the synthesis of ion-conductive compounds in a variety of ways, in the areas of organic and inorganic chemistry. Recently, based on their ion-conducting behavior, porous coordination polymers (PCPs) and metal-organic frameworks (MOFs) have been recognized for their easy design and the dynamic behavior of the ionic components in the structures. These PCP/MOFs consist of metal ions (or clusters) and organic ligands structured via coordination bonds. They could have highly concentrated mobile ions with dynamic behavior, and their characteristics have inspired the design of a new class of ion conductors and transporters. In this Account, we describe the state-of-the-art of studies of ion conductivity by PCP/MOFs and nonporous coordination polymers (CPs) and offer future perspectives. PCP/MOF structures tend to have high hydrophilicity and guest-accessible voids, and scientists have reported many water-mediated proton (H(+)) conductivities. Chemical modification of organic ligands can change the hydrated H(+) conductivity over a wide range. On the other hand, the designable structures also permit water-free (anhydrous) H(+) conductivity. The incorporation of protic guests such as imidazole and 1,2,4-triazole into the microchannels of PCP/MOFs promotes the dynamic motion of guest molecules, resulting in high H(+) conduction without water. Not only the host-guest systems, but the embedding of protic organic groups on CPs also results in inherent H(+) conductivity. We have observed high H(+) conductivities under anhydrous conditions and in the intermediate temperature region of organic and inorganic conductors. The keys to successful construction are highly mobile ionic species and appropriate intervals of ion-hopping sites in the structures. Lithium (Li(+)) and other ions can also be transported. If we can optimize the crystal structures, this could offer further improvements in terms of both conductivity and the working temperature range. Another useful characteristic of PCP/MOFs is their wide application to materials fabrication. We can easily prepare heterodomain crystal systems, such as core-shell or solid solution. Other anisotropic morphologies (thin film, nanocrystal, nanorod, etc.,) are also possible, with retention of the ion conductivity. The flexible nature also lets us design morphology-dependent ion-conduction behaviors that we cannot observe in the bulk state. We propose (1) multivalent ion and anion conductions with the aid of redox activity and defects in structures, (2) control of ion transport behavior by applying external stimuli, (3) anomalous conductivity at the hetero-solid-solid interface, and (4) unidirectional ion transport as in the ion channels in membrane proteins. In the future, scientists may use coordination polymers not only to achieve higher conductivity but also to control ion behavior, which will open new avenues in solid-state ionics.

Concepts: Ammonia, Hydrogen, Chemistry, Ion, Solid, Sodium, Inorganic chemistry, Ionic bond

27

Two new dinuclear dysprosium compounds, [Dy2(HL1)2(PhCOO)2(CH3OH)2] (1) and [Dy2(L2)2(NO3)2(CH3OH)2]·2CH3OH·4H2O (2), have been assembled through applying two ligands with different coordination pockets. The different features of ligands H3L1 and H2L2 result in the distinct coordination geometry of the metal ions in their respective structures. The Dy ions of complexes 1 and 2 were linked by the alkoxide- and hydrazone-O, and display the hula hoop-like and the broken hula hoop-like coordination geometry, respectively. Consequently, these two compounds show distinct magnetic properties. Complex 1 behaves as a single molecule magnet (SMM) with rather slow quantum tunneling rate (τ > 274 ms), while no SMM behavior was observed for complex 2. In addition, the comparison of the structural parameters among the similar Dy2 SMMs with hula hoop-like geometry reveals the significant role played by coordination geometry and magnetic interaction in modulating the relaxation dynamics of SMMs.

Concepts: Chemistry, Magnetism, Ligand, Coordination chemistry, Inorganic chemistry, Terbium, Dysprosium, Dysprosium(III) oxide

27

The first examples of inorganic nitrite complexes of the natural actinides are described, including the structures of the homoleptic thorium(iv) [PPh(4)](2)[Th(NO(2))(6)] and the uranyl(vi) [PPh(4)](2)[UO(2)(NO(2))(4)] complexes; the nitrite ligand can adopt two different coordination modes in the coordination sphere of the uranyl ion and is unstable towards reduction.

Concepts: Ammonia, Ligand, Uranium, Inorganic chemistry, Depleted uranium, Uranyl, Actinides, Uranium trioxide

27

We report here a series of heavier alkaline earth metal complexes with a phosphinoselenoic amide ligand using two synthetic routes. In the first route, the heavier alkaline earth metal bis(trimethylsilyl)amides [M{N(SiMe(3))(2)}(2)(THF)(n)] (M = Ca, Sr, Ba) were treated with phosphinoselenoic amine [Ph(2)P(Se)NH(CHPh(2))] (), prepared by the treatment of bulky phosphinamines [Ph(2)PNH(CHPh(2))] () with elemental selenium in THF, and afforded homoleptic alkaline earth metal complexes of composition [M(THF)(2){Ph(2)P(Se)N(CHPh(2))}(2)] (M = Ca (), Sr (), Ba ()). The metal complexes can also be obtained via salt metathesis route where the alkali metal phosphinoselenoic amides of composition [{(THF)(2)M'Ph(2)P(Se)N(CHPh(2))}(2)] (M' = Na () and K ()) were reacted with respective metal diiodides in THF at ambient temperature. The solid state structures of the alkali metal complexes and alkaline earth metal complexes were established by single crystal X-ray diffraction analysis. In the solid state, alkali metal complexes and are dimeric and form a poly-metallacyclic structural motif. In contrast, complexes are monomeric and a direct metal-selenium bond is observed in each case.

Concepts: Amine, X-ray, Calcium, Metal, Inorganic chemistry, Alkali metal, Alkali, Alkaline earth metal

26

The six-coordinate cobalt(II) complex of formula [Co(tppz)2](tcm)2 exhibits a thermally induced spin-crossover behavior from a high spin (S = (3)/2) at higher temperatures to a low spin (S = (1)/2) at lower temperatures, with the low-spin phase being achieved at T ≤ 200 K.

Concepts: Paramagnetism, Coordination chemistry, Inorganic chemistry, ARIA Charts, Ionic radius, Crystal field theory, Spin states

26

A new unsymmetrical tridentate Schiff base ligand was derived from the 1:1M condensation of ortho-vanillin with 2-mercaptoethylamine. Nickel and palladium complexes were obtained by the reaction of the tridentate Schiff base ligand with nickel(II) acetate tetrahydrate and palladium(II) acetate in 2:1M ratio. In nickel and palladium complexes the ligand was coordinated to metals via the imine N and enolic O atoms. The S groups of Schiff bases were not coordinated to the metals and S-S coupling was occured. The complexes have been found to possess 1:2 Metal:Ligand stoichiometry and the molar conductance data revealed that the metal complexes were non-electrolytes. The complexes exhibited octahedral coordination geometry. The emission spectra of the ligand and its complexes were studied in methanol. Electrochemical properties of the ligand and its metal complexes were investigated in the CH3CN solvent at the 100 mV s(-1) scan rate. The ligand and metal complexes showed both reversible and quasi-reversible processes at this scan rate. The Schiff base and its complexes have been characterized by IR, (1)H NMR, UV/Vis, elemental analyses and conductometry. The crystal structure of nickel complex has been determined by single crystal X-ray diffraction.

Concepts: Coordination complex, Chemical element, Ligand, Coordination chemistry, Solid, Acetic acid, Inorganic chemistry, Schiff base

26

A theoretical study of Li90 P90 , which possesses a circular double-helix structure that resembles the Watson-Crick DNA structure, is reported. This is a new bonding motif in inorganic chemistry. The calculations show that the molecule might become synthesized and that it could be a model for other inorganic species which possess a double-helix structure.

Concepts: DNA, Oxygen, Gene, Physics, Molecule, Chemistry, Atom, Inorganic chemistry