High pressure stabilization and emergent forms of PbH4

A wide decomposition pressure range of 132 GPa is predicted for PbH4 above which it emerges in very different forms compared with its group-14 congeners. This triply Born-Oppenheimer system is a nonmolecular, three-dimensional, metallic alloy, despite a prominent layered structure. A significant number of enthalpically near-degenerate structures, with exceedingly small energy barriers for distortions, and characteristic instabilities in the phonon spectra suggest that even at very high pressures PbH4 may exhibit both metallic and liquidlike properties and sublattice or even full melting.     

Relativity and the lead-acid battery

The energies of the solid reactants in the lead-acid battery are calculated ab?initio using two different basis sets at nonrelativistic, scalar-relativistic, and fully relativistic levels, and using several exchange-correlation potentials. The average calculated standard voltage is 2.13?V, compared with the experimental value of 2.11?V. All calculations agree in that 1.7-1.8?V of this standard voltage arise from relativistic effects, mainly from PbO2 but also from PbSO4.     

Preliminary thermal characterization of natural resins from different botanical sources and geological environments

The preliminary studies on thermal behavior of differently aged natural resins from Russia (Khatanga), Dominican Republic (El Valle), Colombia and Poland (Jantar) were performed. Thermal stability and behavior under elevated temperature were investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC), while the differences in the structure and composition by FT-IR spectroscopy. Analyzed resins show different thermal effects during heating suggesting that possible post-reactions and structural changes occurred. TG results indicated that Dominican, Russian and Colombian resins present relatively high thermal stability under air conditions in the range of 228–300 °C, whereas the mass loss of 5mass% at about 217 °C was observed for Baltic amber. During DSC experiments, the analyzed resins expose thermal events which make impossible determination of glass transition temperature in a raw sample. The results indicate that both TG and DSC cannot be considered as methods for age dating of natural resins and more advanced techniques should be applied. Careful analysis of FT-IR data in the carbonyl region may provide additional information about the composition and history of the natural resin.

     

From nanostrips to nanorings: the elastic properties of gold-glued polyauronaphthyridines and polyacenes

The previously proposed flat 2,6-diauro-1,5-naphthyridine polymers were bent to closed rings with up to 12 monomers. Their bending energies and lowest in-plane deformation frequencies were calculated at the DFT level using quasirelativistic pseudopotentials for gold. The ring-formation energies were compared with those for polyacene rings and found to be of the same order of magnitude, suggesting sufficient stability for the predicted polyauronaphthyridines. As function of the ring radius, r, the frequencies and deformation energies were shown to behave as r(-2) and r(-1), respectively. The molecules thus behave as classical elastic bodies.     

Basis-set limit of the aurophilic attraction using the MP2 method: the examples of [ClAuPH3]2 dimer and [P(AuPH3)4]+ ion

The basis-set limit of the aurophilic attraction is studied at the MP2 level for the free model dimer [ClAuPH(3)](2) and for a [P(AuPH(3))(4)](+) ion. The latter system is found to prefer a C(4v) symmetry, instead of T(d), in agreement with Li and Pyykko [Inorg. Chem. 32, 2630 (1993)] but in contradiction to recent results of Fang and Wang [J. Phys. Chem. A. 111, 1562 (2006)]. The Karlsruhe split valence and the Dunning correlation-consistent basis sets converge to the same limit.     

Structure and bonding of the MCN molecules, M=Cu,Ag,Au,Rg

High-precision calculations are reported for the title series with M=Cu, Ag, Au, using CCSD(T) with the latest pseudopotentials and basis sets up to cc-pVQZ. The bond lengths for M=Cu, Ag, Au agree with experiment within better than 1 pm. The role of deep-core excitations is studied. The second-order spin-orbit effects are evaluated at the density functional theory level, including M=Rg. A qualitative bonding analysis suggests multiple M-C bonding. The calculated vibrational frequencies are expected to be more accurate than the available experimental estimates. The M-C bond lengths obey Cu相似文献   

Synthesis and Preliminary Anticancer Activity Assessment of N-Glycosides of 2-Amino-1,3,4-thiadiazoles

The addition of 2-amino-1,3,4-thiadiazole derivatives with parallel iodination of differently protected glycals has been achieved using a double molar excess of molecular iodine under mild conditions. The corresponding thiadiazole derivatives of N-glycosides were obtained in good yields and anomeric selectivity. The usage of iodine as a catalyst makes this method easy, inexpensive, and successfully useable in reactions with sugars. Thiadiazole derivatives were tested in a panel of three tumor cell lines, MCF-7, HCT116, and HeLa. These compounds initiated biological response in investigated tumor models in a different rate. The MCF-7 is resistant to the tested compounds, and the cytometry assay indicated low increase in cell numbers in the sub- G1 phase. The most sensitive are HCT-116 and HeLa cells. The thiadiazole derivatives have a pro-apoptotic effect on HCT-116 cells. In the case of the HeLa cells, an increase in the number of cells in the sub-G1- phase and the induction of apoptosis was observed.     

Possible schemes of photoassociation processes in the KLi molecule with newly calculated potential energy curves

We present four promising schemes for photoassociative formation of KLi molecule in its ground electronic state. Analysis is based on newly calculated adiabatic potentials supported by transition dipole moments and Franck-Condon factors.     

Synthesis and Characterization of Platinum(IV) Complexes Containing 1-Phenyl-1H-pyrazole and α-Diimine Ligands

The paper deals with the synthesis of a series of cationic [Pt(ppz)₂(N^N)]²⁺ complexes containing deprotonated 1-phenyl-1H-pyrazole as cyclometallating (C^N) ligands and α-diimines (N^N) in the form of water-soluble salts with OTf⁻ (trifluoromethanesulfonate) counter ions. These complexes were obtained from cis-[Pt(ppz)₂Cl₂] through chloride ligands substitution with α-diimines. The complexes were identified by means of NMR spectroscopy and their molecular structures were confirmed by X-ray crystallography. The photophysical properties of these complexes were studied in detail. These complexes showed strong luminescence in MeOH/EtOH 1 : 1 glasses at 77 K but were almost non-emitting in MeCN solutions at room temperature. Their emission properties were compared to analogues Ir^III complexes.