Evidence for the dimer-of-(mixed-valent dimers) configuration in tetranuclear {(μ<Subscript>4</Subscript>-TCNX)[Ru(NH<Subscript>3</Subscript>)<Subscript>5</Subscript>]<Subscript>4</Subscript>}<Superscript>8+</Superscript>, TCNX = TCNE and TCNQ,from DFT calculations

Abstract  DFT calculations of the complex ions {(μ₄-TCNX)[Ru(NH₃)₅]₄}⁸⁺, TCNX = tetracyanoethene (TCNE) and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ), yield triplet state energy minimum structures with nonplanar bridging ligands. The calculated C–C bond distances and twist angles confirm considerable metal-to-ligand electron transfer from the metal centers to the TCNE and TCNQ bridges in the lowest triplet and singlet states. The resulting situation, involving a weak interaction between two strongly coupled malonodinitrilato-bridged Ru^2.5Ru^2.5 entities (Class III), agrees with experimental results; the near-orthogonality found for the ground states of the molecular ions explains the observed magnetic exchange coupling between two S = 1/2 sites, the 1,258 cm⁻¹ absorption in the IR spectrum of the TCNE complex, and the reversible two-electron oxidation. The nitrile stretching frequency shifts were reasonably reproduced by the calculations. A density-of-states representation for the TCNQ complex shows a rather different electronic structure in comparison to that for the formally related {(μ₄-TCNQ)[Re(CO)₃(bpy)]₄}⁴⁺, in particular a different frontier orbital situation. In contrast to the (TCNQ⁰)(Re^I)₄ situation, the tetraruthenium species with an approximate (TCNX²⁻)(Ru^2.5)₄ formulation represent unconventional mixed-valent tetranuclear compounds; in other words, weakly coupled pairs of strongly coupled dinuclear moieties. EPR spectroscopy at the W band frequency (95 GHz) of the TCNE compound confirms that the reduction of the complex leads to the oxidation of TCNE²⁻ to yield a (TCNE^•−)(Ru^II)₄ species. Graphical abstract  

Luminescent Properties of Hexanuclear Molybdenum(II) Chloride Clusters Containing Thiolate Ligands

The emission spectra of a series of molybdenum(II) chloride clusters containing thiolate ligands, [Mo₆(μ₃-Cl)₈(SR)₆]²⁻ (R = Et, Bu, Ph, Bn), have been recorded. These complexes all show a broad emission at ~700 nm after excitation at 337, 400 and 410 nm. Determination of the excited state lifetimes and quantum yields of these complexes in acetonitrile reveals that (Bu₄N)₂[Mo₆(μ₃-Cl)₈(SPh)₆] displays the longest excited state lifetime of this series (26 μs at 296 K).

Dimerization in Acetonitrile of [H6PMo9O34]3− into [P2Mo18O62]6−: Structural Characterization of the Tetrabutyl Ammonium Salt

The trivacant heteropolyanion A-α[PMo₉O₃₁(OH₂)₃]³⁻ spontaneously dimerizes in acetonitrile to form the Dawson complex [P₂Mo₁₈O₆₂]⁶⁻. A rapid new quantitative preparation of the sodium salt of this Dawson complex is described. In addition, the structure of TBA₅[HP₂Mo₁₈O₆₂] is given and the featuring data compared with the isomorphous sodium salt (space group C2/c).

Diversity of Functionalized Germanium Zintl Clusters: Syntheses and Theoretical Studies of [Ge9PdPPh3]3− and [Ni@(Ge9PdPPh3)]2−

Abstract  A new Zintl cluster [Ge₉PdPPh₃]³⁻ has been isolated as (2,2,2-crypt)K⁺ salt through the reaction of K₄Ge₉ and Pd[PPh₃]₄ in ethylenediamine solutions and characterized via single-crystal X-ray crystallography. The as-prepared bimetallic [Ge₉PdPPh₃]³⁻ cluster could successfully trap a nickel atom to form a trimetallic cluster [Ni@(Ge₉PdPPh₃)]²⁻. The coordination of Ge₉ ⁴⁻ by PdPPh₃ induces a one-electron oxidation and encapsulation of the Ni atom into the Ge₉ ³⁻ cage leads to a further one-electron oxidation and a geometry transformation from C_4v (nido) to C_3v (closo). Graphical Abstract   Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

Electrochemical and photoelectrochemical characterization of CuFeO2 single crystal

CuFeO₂ single crystal, synthesized by the flux method, is a narrow band gap semiconductor crystallizing in the delafossite structure with a direct optical transition of 1.63 eV. The oxide exhibits a good chemical stability; the semi-logarithmic plot gave an exchange current density of 0.60 μA cm⁻² in KCl (0.5 M) electrolyte. CuFeO₂ shows p-type conductivity; the origin of acceptors Cu²⁺ results from oxygen insertion in the layered lattice where most of excess holes are trapped in surface-polaron states. The electrochemical study is confined in the (a,b) plane and reversible oxygen intercalation is evidenced from the intensity potential characteristics. The detailed photoelectrochemical studies have been reported for the first time on the single crystal. The photocurrent is ascribed to the transfer Cu⁺:3d→3d. The capacitance measurement (C⁻²–V) shows a linear behavior from which a flat band potential of +0.54 V_SCE and a density N _A of 1.60 × 10¹⁸ cm⁻³ were determined. The valence band, located at 5.33 eV below vacuum, is made up of Cu-3d orbital typical of delafossite oxides. The Nyquist plot shows a semicircle attributed to a capacitive behavior with a low density of surface states within the gap. The centre is localized below the real axis with an angle of 16.2° ascribed to a constant phase element (CPE), a single barrier of the junction CuFeO₂/electrolyte and one relaxation time of the electrical equivalent circuit.

A comparative study of hydrothermal and sol–gel methods in the synthesis of MnO<Subscript>2</Subscript> nanostructures

In this work, MnO₂ nanostructure powders with different crystalline phases have been successfully prepared by hydrothermal and sol–gel methods. The obtained products were characterized by XRD and SEM techniques and their crystallographic phases and morphological properties compared. Results showed that α-MnO₂, β-MnO₂, and δ-MnO₂ nanorods were synthesized by hydrothermal method and γ-MnO₂ polymorph was obtained by sol–gel method.

Chemistry,commentary and community: Discussion of “The NaDyBr<Subscript>4</Subscript> complex: its molecular structure and thermodynamic properties” by Varga and Hargittai

The molecular geometries, relative stabilities, binding energies, and dissociation energies of NaDyBr₄ and its molecular ion are discussed. Both the bidentate and tridentate isomers are stable for the neutral species, while only the bidentate form is stable for NaDyBr₄ ⁺.

A Chain Catalytic Reaction Involving Pd Cluster as Chain Carrier

   α−Alkyl- and α,α′-dialkyl-substituted benzylic alcohols PhCR′R′′OH (R′=H, Me, Et, Bu; R′′=H, Me) are transformed to the corresponding dilbenzylic ethers and water in acid-free neat substrate media shortly after the addition of the palladium(I) cluster [Pd₄(CO)₄(OAc)₄] (1). During the catalytic reaction occurring under anaerobic conditions, cluster 1 is gradually decomposed to form Pd black, whereas neither original cluster 1 nor Pd black is responsible for the observed reaction. The true reaction catalyst is generated from cluster 1 after a short induction period. On the basis of the reaction kinetics and the HREM, X-ray diffraction, DTA-TG, and elemental analysis data, the catalytic dehydration is suggested to occur through a nonradical chain mechanism involving an unstable intermediate Pd cluster as the chain carrier.

Spectrometric and theoretical investigation of the structures of Cu and Pb/DTPA complexes

Spectrometric and theoretical tools have been employed in this study in order to elucidate the structures of DTPA (diethylenetriaminepentaacetic acid) complexed to copper and lead. Mass spectrometry allowed determining the 1:1 stoichiometry of metal:ligand, while infrared spectroscopy demonstrated that both N and O are sites for complexation. ¹³C NMR analysis showed the existence of free and complexed carboxyl groups, due to a straight singlet at 180.7 ppm (free carboxylic ¹³C) and to a broad signal at 179.3 ppm (complexed carboxylic ¹³C, ² J _Pb…O=C). A distorted NMR signal were observed for the Cu–DTPA carboxyl group, due to the Cu²⁺ paramagnetism. Based on the spectrometric evidences for the metal–DTPA structures, DFT optimizations were carried out and an octahedral-like arrangement for the Cu complex and a “shell-like” arrangement for the Pb complex, both hexa-coordinated, were then proposed for the structures of the titled compounds.

Consistency of practical salinity measurements traceable to primary conductivity standards: Euromet project 918

Measurements of practical salinity are based on conductivity measurements, which are traceable to the conductivity of a defined KCl reference solution. The conductivity of this reference solution must be traceable to the SI in order to state a reliable uncertainty for practical salinity measurements and to guarantee their comparability. Currently, the conductivity ratios from various old standard seawater batches are compared instead. However this method is inadequate on a long time-scale, which is important for oceanography studies, because it lacks a time-invariant reference. Therefore the equivalence of conductivity measurements traceable to primary conductivity standards has been investigated in Euromet project 918. Several European metrology institutes measured the conductivity of a 5 S/m KCl solution and the practical salinity of IAPSO standard seawater. The study estimates relative standard uncertainties to be of the order of 10⁻⁴ to 10⁻³ for such measurements.

Structure and chromotropic properties of mono- and binuclear mixed-ligand nickel(II) complexes containing 1,3-diketonate and polyamine ligands

Abstract  Mixed-ligand Ni^II complexes have been synthesized with 1,3-diketonate and bulky tri- or tetra-amine ligands. Their structures were determined by X-ray crystallography, and solvatochromic behavior was examined by UV–vis–NIR spectroscopy. Steric effects of the bulky ligands on the coordination distances and spectral properties are discussed. Graphical Abstract  

Nonlinear magneto-optical effects and photomagnetism of electrochemically synthesized molecule-based magnets

This article describes novel optical functionalities such as photomagnetic effects and magnetization-induced second harmonic generation (MSHG) in several cyano-bridged metal assemblies. Single crystal- and film-types of a cyano-bridged Cu–Mo bimetallic assembly, , were electrochemically prepared. When this compound was irradiated with light, spontaneous magnetization with a Curie temperature (T _C) of 23 K was observed. Electrochemically prepared Fe^II[Cr^III(CN)₆]_2/3·5H₂O thin film, which was a ferromagnet with T _C=21 K, showed photoreduced magnetization. This photomagnetism is due to the change of ferromagnetic coupling between Fe^II and Cr^III. MSHG was observed in Cs^ICo^II[Cr^III(CN)₆]·0.5H₂O. This -type Prussian blue analog-based magnet is proven to be a piezoelectric ferromagnet, i.e., condensed matter with both piezoelectric and ferromagnetism. This MSHG is due to the coupling between a piezoelectric structure of and ferromagnetism with a T _C of 46 K.

Synthesis and Crystal Structure of a Heteronuclear Fe–Ru Silyl Complex*

The reaction of the iron metalate [Fe{Si(OMe)₃}(CO)₃(dppm-P)]⁻ (1b) with [Ru(CO)₃Cl(μ-Cl)]₂ afforded the heterodinuclear complex [(OC)₃{(MeO)₃Si}Fe(μ-dppm)Ru(CO)₃Cl)] (Fe–Ru) (3) in which a long Fe–Ru separation of 2.956(1) ? has been crystallographically evidenced. It was shown by density functional theory (DFT) calculations to correspond to the minimum-energy structure. Upon treatment of the corresponding hydrido complex [HFe{Si(OMe)₃}(CO)₃(dppm-P)] (1a) with [Ru(CO)₃Cl(μ-Cl)]₂, the chloride-bridged tetranuclear hydrido complex [(OC)₃{(MeO)₃Si}Fe(H)(μ-dppm)Ru(CO)₂Cl(μ-Cl)]₂ (4) was formed in which the Fe and Ru centers are only linked via bridging dppm ligands. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

Mass transfer effects on the electropolymerization current efficiency of 3-methylthiophene in the magnetic field

3-Methylthiophene was chosen as a representative conducting polymer precursor, whose electropolymerization proceeds through the coupling of cation radicals. The density of the solution that contains electrogenerated 3-methylthienyl radicals and early oligomers is higher than the density of the surrounding solution, and at low (<0.2 M) monomer concentrations the diffusion layer falls, compromising the electropolymerization current efficiency. Applying a homogeneous magnetic field (3.0 T) perpendicular to the electrode surface (θ=0°) produces concentration gradient paramagnetic forces (F _∇C) that hold the diffusion layer in contact with the electrode. This gives time for more oligomers to get oxidized and for more cation radicals to couple so that the current efficiency increases from 0.028 to 0.037 at 0.05 M of monomer concentration, and from 0.051 to 0.071 at 0.1 M. With the magnetic field parallel to the electrode surface (θ=90°) Lorenz forces causing magnetohydrodynamic convection, in combination with F _∇C forces keeping the flow pattern in contact with the electrode, increase the current efficiency even more, to 0.048 at 0.05 M of monomer concentration, and to 0.076 at 0.1 M. At higher monomer concentrations (>0.2 M), the rate of radical coupling is evidently fast enough so that, even in the absence of a magnetic field, no natural convection effects are observed and the current efficiency (0.7–0.8) is not affected by the magnetic field.

Modeling of solvent viscosity effects on the electroreduction of Pt(II) aquachlorocomplexes

Solvent dynamics effects on the electroreduction of [PtCl₃(H₂O)]⁻ at a mercury electrode are explored in the framework of Sumi–Marcus model using an efficient computational scheme. According to results of density functional calculations, the second electron transfer step may be regarded as rate controlling. The nonmonotonous influence of solvent viscosity on the reaction rate is predicted and explained in terms of the saddle point avoidance. The results of model calculations are employed to interpret experimental data reported earlier in the literature.

Branched trichain sulfosuccinates as novel water in CO2 dispersants

A series of highly branched trichain sulfosuccinate surfactants have been synthesized and studied in condensed CO₂ and aqueous environments. Aqueous critical micelle concentrations (CMCs) showed a general trend of increasing CMC with decreasing chain length, whereas increased branching appeared to increase solubility in CO₂ and aid the dispersion of water. Near infrared spectra confirmed observed cloud with a large increase in solubility above the cloud pressures in this solvent.

Synthesis and dopamine receptor binding affinity of 4H-thiochromenoapomorphines

Abstract  The synthesis of 4H-thiochromene derivatives of apomorphines, a novel class of isoquinoline alkaloid-related compounds, has been achieved by different O-dealkylation methods applied on previously published heteroring-fused aporphinoids. Detailed DFT study has been presented regarding the mechanism of the L-selectride-mediated multiple O-dealkylation of a seven-ring aporphine analogue. Dopamine-binding tests confirmed the essential function of 11-hydroxy moiety of the aporphine skeleton and revealed a remarkable D₁ over D₂ specificity for the derivative having the 4H-thiochromene ring system attached to positions 2 and 3 of the aporphine backbone. Graphical Abstract  

The effects of characteristics of substituents on toxicity of the nitroaromatics: HiT QSAR study

The present study applies the Hierarchical Technology for Quantitative Structure–Activity Relationships (HiT QSAR) for (i) evaluation of the influence of the characteristics of 28 nitroaromatic compounds (some of which belong to a widely known class of explosives) as to their toxicity; (ii) prediction of toxicity for new nitroaromatic derivatives; (iii) analysis of the effects of substituents in nitroaromatic compounds on their toxicity in vivo. The 50% lethal dose concentration for rats (LD₅₀) was used to develop the QSAR models based on simplex representation of molecular structure. The preliminary 1D QSAR results show that even the information on the composition of molecules reveals the main tendencies of changes in toxicity. The statistic characteristics for partial least squares 2D QSAR models are quite satisfactory (R ² = 0.96–0.98; Q ² = 0.91–0.93; R ² _test = 0.89–0.92), which allows us to carry out the prediction of activity for 41 novel compounds designed by the application of new combinations of substituents represented in the training set. The comprehensive analysis of toxicity changes as a function of substituent position and nature was carried out. Molecular fragments that promote and interfere with toxicity were defined on the basis of the obtained models. It was shown that the mutual influence of substituents in the benzene ring plays a crucial role regarding toxicity. The influence of different substituents on toxicity can be mediated via different C–H fragments of the aromatic ring. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

CAL3JHH: a Java program to calculate the vicinal coupling constants (<Superscript>3</Superscript><Emphasis Type="Italic">J</Emphasis><Subscript>H,H</Subscript>) of organic molecules

Here, we present a free web-accessible application, developed in the JAVA programming language for the calculation of vicinal coupling constant (³ J _H,H) of organic molecules with the H–C_sp3–C_sp3–H fragment. This JAVA applet is oriented to assist chemists in structural and conformational analyses, allowing the user to calculate the averaged ³ J _H,H values among conformers, according to its Boltzmann populations. Thus, the CAL3JHH program uses the Haasnoot–Leeuw–Altona equation, and, by reading the molecule geometry from a protein data bank (PDB) file format or from multiple pdb files, automatically detects all the coupled hydrogens, evaluating the data needed for this equation. Moreover, a “Graphical viewer” menu allows the display of the results on the 3D molecule structure, as well as the plotting of the Newman projection for the couplings. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.