Covalent Bonding in Au(BO) 2 − and Au(BS) 2 −

We perform in this work a comprehensive first-principles investigation on the geometric and electronic structures of Au(BO) ₂ ^? and Au(BS) ₂ ^? which are valent isoelectronic to the well-known Au(CN) ₂ ^? monoanion. Au(BO) ₂ ^? and Au(BS) ₂ ^? complexes prove to possess linear ground-state structures similar to Au(CN) ₂ ^? and the BO^? and BS^? ligands in them are found to be coordinated terminally via boron atoms to gold centers which are weakly negatively charged. Au–B bonds in Au(BO) ₂ ^? and Au(BS) ₂ ^? appear to have higher Wiberg bond indices (0.79 and 0.80) and more covalent components (60 and 53 %) than the corresponding values of Au–C interaction in Au(CN) ₂ ^? (0.67 and 39 %, respectively) at the same theoretical levels. Their Au–B bifurcation values of the electronic localization function also turn out to be higher than Au–C. These results strongly suggest that the Au–B bonds in Au(BO) ₂ ^? and Au(BS) ₂ ^? with multiple-bond character possess stronger covalent characters than Au–C in Au(CN) ₂ ^? .     

Novel red-emitting phosphors, (Mg(1−x−y)MnxDyy)Al2Si2O8 and (Mg(1−x−y)MnxTmy)Al2Si2O8

Mn⁴⁺ doped and Dy³⁺, Tm³⁺ co-doped MgAl₂Si₂O₈-based phosphors were prepared by conventional solid state reaction at 1,300 °C. They were characterized by thermogravimetry, differential thermal analysis, X-ray powder diffraction, photoluminescence, and scanning electron microscopy. The luminescence mechanism of the phosphors, which showed broad red emission bands in the range of 600–715 nm and had a different maximum intensity when activated by UV illumination, was discussed. Such a red emission can be attributed to the ²E → ⁴A₂ transitions of Mn⁴⁺.     

Bioresorbable carbonated hydroxyapatite Ca10−xNax(PO4)6−x(CO3)x(OH)2 powders for bioactive materials preparation

The purpose of this work was to find and investigate a correlation between the carbonate ion content in crystalline lattice and defect structure, and solubility of the materials; finally, to prepare the materials under study for in vitro tests. Various techniques, such as XRD, FTIR, TEM, FESEM/EDX, TG/DTA, AES (ICP), wet chemical analysis, Ca-ionometry, microvolumetric analysis of evolved CO₂, BET adsorption, were applied to determine the efficiency of carbonate substitution, and to quantify the elemental composition, as well as to characterize the structure of the carbonated hydroxyapatite and the site(s) of carbonate substitution,. It was shown that AB-type substitution prevails over other types with the carbonate content increase. According to in vitro tests, the bioactivity of the samples is correlated with the carbonate content in carbonate-doped hydroxyapatite due to accumulation of defects in carbonated hydroxyapatite nanocrystals.      

Synthesis and physical and chemical characterization of Ca10−xAgx(PO4)6(OH)2−xx apatites

The synthesis of calcium-silver hydroxyapatites of composition Ca_10−xAg_x(PO₄)₆(OH)_2−xx is discussed, together with their physical and chemical properties. Samples prepared both by dry process and by double decomposition were characterized using a variety of analytical techniques (chemical analysis, X-ray diffraction, infrared spectroscopy). The lattice parameters a and c increase linearly with the amount of silver added. The increase is attributed to the preferential substitution of the silver ion in site me (I) of these apatites.     

Negative ion photoelectron spectroscopy of solvated electron cluster anions, (H2O) n − and (NH3) n −

The photodetachment spectra of (H₂O) _n ^=2?69/? and (NH₃) _n ^=41?1100/? have been recorded, and vertical detachment energies (VDEs) were obtained from the spectra. For both systems, the cluster anion VDEs increase smoothly with increasing sizes and most species plot linearly withn ^?1/3, extrapolating to a VDE (n=∞) value which is very close to the photoelectric threshold energy for the corresponding condensed phase solvated electron system. The linear extrapolation of this data to the analogous condensed phase property suggests that these cluster anions are gas phase counterparts to solvated electrons, i.e. they are embryonic forms of hydrated and ammoniated electrons which mature with increasing cluster size toward condensed phase solvated electrons.     

The formation of the Ba(CuOx)1−y(CO3)y

Carbocuprate compounds are generally described as multiple perovskites with CO ₃ ² - and Cu-O alternating layers containing Ba and/or Sr; they have gained an unexpected importance in the high temperature superconductivity field, because many compounds with transition temperature above 100 K belong to this class of materials.We have started a systematic study on phase formation and stabilisation in the Ba-Cu-C-O system in the temperature range 20-600°C, by using thermal analysis techniques. Starting from a BaCO₃-BaO₂-CuO mixture (311 mol), a new phase isomorphic with BaCO₃ formed after heat treatment above 390°C in air. TG, DSC, EGA and high temperature XRD were employed to follow the complex interaction of the reactants with the atmosphere and the formation of the new phase.     

Photoelectron spectroscopy of (CO2)n(H2O) m − clusters

Photoelectron spectra of (CO₂)_nH₂O^? (2≤n≤8) and (CO₂)_n(H₂O) ₂ ^? (1≤n≤2) were measured at the photon energy of 3.49 eV. The spectra show unresolved broad features, which are approximated by Gaussians. The vertical detachment energies (VDEs) were determined as a function of the cluster size. For (CO₂)_nH₂O^?, the VDE-n plots exhibit a sharp discontinuity between n=3 and 4; the VDE value is ≈3.5 eV at n=3, while it drops down abruptly to 2.59 eV at n=4. This discontinuity in VDE is ascribed to "core switching" at n=4; a C₂O ₄ ^? dimer anion forms the core of (CO₂)_nH₂O^? for n≤3, while a monomer CO ₂ ^? is the core for n≥4. The (CO₂)₂(H₂O) ₂ ^? ion has a VDE of 2.33 eV, indicating the presence of a CO ₂ ^? monomer core in the binary clusters containing two H₂O molecules.     

Radical C−H Trifluoromethoxylation of (Hetero)arenes with Bis(trifluoromethyl)peroxide

Trifluoromethoxylated (hetero)arenes are of great interest for several disciplines, especially in agro- and medicinal chemistry. Radical C−H trifluoromethoxylation of (hetero)arenes represents an attractive approach to prepare such compounds, but the high cost and low atom economy of existing ^. OCF₃ radical sources make them unsuitable for the large-scale synthesis of trifluoromethoxylated building blocks. Herein, we introduce bis(trifluoromethyl)peroxide (BTMP, CF₃OOCF₃) as a practical and efficient trifluoromethoxylating reagent that is easily accessible from inexpensive bulk chemicals. Using either visible light photoredox or TEMPO catalysis, trifluoromethoxylated arenes could be prepared in good yields under mild conditions directly from unactivated aromatics. Moreover, TEMPO catalysis allowed for the one-step synthesis of valuable pyridine derivatives, which have been previously prepared via multi-step approaches.     

Photochromic Coatings Containing Ag(Cl1−xBrx) Microcrystals

Photochromic ormosil coatings containing Ag(Cl_1–x Br _x ) microcrystals were formed on a glass substrate via the sol-gel process. Methyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane were used as starting materials of the ormosil matrices. 3-chloropropyltrimethoxysilane and bromophenyltrimethoxysilane were added as halogen sources and silver colloidal dispersion was introduced into the precursor sol. The coated glass became transparent and photosensitive after Ag(Cl_1–x Br _x ) microcrystals were precipitated in the coatings above 300°C. Insertion of a SiO₂ buffer layer between the substrate and photochromic layer was effective in preventing Ag⁺ migration into the substrate. Photochromic performances were improved by the substitution of Cl with Br and the incorporation of a minute amount of Cu.     

Structure of the Mo(CN)8 4− ion

Summary The question of the hybridization of the atomic orbitals of Mo in the Mo(CN)₈ ^4– ion is examined, and it is shown that the dodecahedral structure can exist without the participation off electrons.     

The electrochemical Peltier heats of Fe(CN) 6 3− /Fe(CN) 6 4− system at 295.15 K

A specially designed thermo-electrochemical calorimeter was applied to measure the electrochemical Peltier heats (EPH) of Fe(CN) ₆ ^3?/4? system at 295.15 K. The curves of the electrode potential changes and temperature changes against time for Fe(CN) ₆ ^3?/4? couple with five groups of different concentrations were obtained under the condition of various constant-current polarizations. The EPH values for the considered electrode reaction are determined to be ?41.31, ?42.73, ?44.28, ?45.87, and ?46.65 kJ mol^?1 at the respective concentrations of 0.125, 0.175, 0.225, 0.275, and 0.300 mol dm^?3; and the EPH and the apparent enthalpy change corresponding to the infinite dilution to be ?37.42 and ?84.10 kJ mol^?1 at 295.15 K, respectively.     

Small Gold(I) and Gold(I)–Silver(I) Clusters by C−Si Auration

Auration of o-trimethylsilyl arylphosphines leads to the formation of gold and gold–silver clusters with ortho-metalated phosphines displaying 3c–2e Au−C−M bonds (M=Au/Ag). Hexagold clusters [Au₆L₄](X)₂ are obtained by reaction of (L−TMS)AuCl with AgX, whereas reaction with AgX and Ag₂O leads to gold–silver clusters [Au₄Ag₂L₄](X)₂. Oxo-trigold(I) species [Au₃O]⁺ were identified as the intermediates in the formation of the silver-doped clusters. Other [Au₅], [Au₄Ag], and [Au₁₂Ag₄] clusters were also obtained. Clusters containing PAu−Au−AuP structural motif display good catalytic activity in the activation of alkynes under homogeneous conditions.     

Ni(II) Precatalysts Enable Thioetherification of (Hetero)Aryl Halides and Tosylates and Tandem C−S/C−N Couplings

Ni-catalyzed C−S cross-coupling reactions have received less attention compared with other C-heteroatom couplings. Most reported examples comprise the thioetherification of most reactive aryl iodides with aromatic thiols. The use of C−O electrophiles in this context is almost uncharted. Here, we describe that preformed Ni(II) precatalysts of the type NiCl(allyl)(PMe₂Ar’) (Ar’=terphenyl group) efficiently couple a wide range of (hetero)aryl halides, including challenging aryl chlorides, with a variety of aromatic and aliphatic thiols. Aryl and alkenyl tosylates are also well tolerated, demonstrating, for the first time, to be competent electrophilic partners in Ni-catalyzed C−S bond formation. The chemoselective functionalization of the C−I bond in the presence of a C−Cl bond allows for designing site-selective tandem C−S/C−N couplings. The formation of the two C-heteroatom bonds takes place in a single operation and represents a rare example of dual electrophile/nucleophile chemoselective process.     

C−H Bond Activation by Iridium(III) and Iridium(IV) Oxo Complexes

Oxidation of an iridium(III) oxo precursor enabled the structural, spectroscopic, and quantum-chemical characterization of the first well-defined iridium(IV) oxo complex. Side-by-side examination of the proton-coupled electron transfer thermochemistry revealed similar driving forces for the isostructural oxo complexes in two redox states due to compensating contributions from H⁺ and e⁻ transfer. However, C−H activation of dihydroanthracene revealed significant hydrogen tunneling for the distinctly more basic iridium(III) oxo complex. Our findings complement the growing body of data that relate tunneling to ground state properties as predictors for the selectivity of C−H bond activation.     

Simple fast preparation of neutral palladium(II) complexes with SnCl− 3 and Cl− ligands

A new method for preparing neutral trichlorostannate complexes of Pd^II, based on the interaction between solid [PdCl₂(MeCN)₂] and SnCl₂ suspension and a solution of an appropriate ligand in CH₂Cl₂, has been developed. The analogous method can be used to prepare complexes without tin, as well as compounds containing mixed anionic ligands. A number of complexes (including several new compounds) with amines, phosphines and diene ligands have been obtained by these methods. The procedures are simple and fast – the total preparation time (without recrystallisation) is ca. 30 min.     

Low-Frequency Sub-Terahertz Absorption in HgII−XCN−FeII (X=S,Se) Coordination Polymers

Self-assembly Fe^II complexes of phenazine (Phen), quinoxaline (Qxn), and 4,4′-trimethylenedipyridine (Tmp) with tetrahedral building blocks of [Hg^II(XCN)₄]²⁻ (X=S or Se) formed six new high-dimensional frameworks with the general formula of [Fe(L)_m][Hg(XCN)₄]⋅solvents (L=Phen, m/X=2/S, 1 ; L=Qxn, m/X=2/S, 2 ; L=Qxn, m/X=1/S, 3 ; L=Qxn, m/X=1/Se, 3-Se ; L=Tmp, m/X=1/S, 4 ; and L=Tmp, m/X=1/Se, 4-Se ). 1 , 3 , and 3-Se show an intense sub-terahertz (sub-THz) absorbance of around 0.60 THz due to vibrations of the solvent molecules coordinated to the Fe^II ions and crystallization organic molecules. In addition, crystals of 1 , 4 , and 4-Se display low-frequency Raman scattering with exceptionally low values of 0.44, 0.51, and 0.53 THz, respectively. These results indicate that heavy metal Fe^II−Hg^II systems are promising platforms to construct sub-THz absorbers.     

Photoelectron spectroscopy of silicon and germanium-fluorine binary cluster anions (SinF m − , GenF m − )

Electronic properties of silicon-fluorine and germanium-fluorine cluster anions (Si_nF _m ^? n = 1–9, m = 1–3, Ge_nF _m ^? ; n =1–9, m = 1–3) were investigated by photoelectron spectroscopy using a magnetic-bottle type electron spectrometer. The binary cluster anions were generated by a laser vaporization of a silicon/germanium rod in an He carrier gas mixed with a small amount of SiF₄ or F₂ gas. Comparison between photoelectron spectra of Si_nF^?/Ge_nF^? and Sin /Gen (n = 4–9) gives the insight that the doped F atom can remove one electron from the corresponding Sin _n ^? /Ge _n ^? cluster without any serious rearrangement of Sin/Gen framework, because only the first peak of Si _n ^? /Ge _n ^? , corresponding singly occupied molecular orbital (SOMO), disappears and other successive spectral features are unchanged with the F atom doping