New borate LaB5O8(OH)2 · 1.5H2O with a {4[3T + Δ]∞∞ + Δ}∞∞∞ complex framework. Its place in the structural system based on symmetry and topology analysis in terms of the OD theory

Crystals of a new hydrous rare-earth borate LaB₅O₈(OH)₂ · 1.5H₂O(1), space group P2₁/n, are prepared hydrothermally. The crystal structure is solved using the heavy-atom method without a priori knowledge of the chemical formula. The complex anionic radical is built of pleated layers, which are structurally and topologically related to layered pentaborates but do not have the fifth boron polyhedron in the building block; these layers are linked into the {4[3T + Δ]_∞∞ + [Δ]}_∞∞∞ framework through BO₃ triangles. Lanthanum atoms reside in valleys of the layers; framework voids are occupied by water molecules. The framework of the new borate in its topology and symmetry is an analogue of the centrosymmetric variety of lead borate (hilgardite): in both, the layers are apolar and are type I in terms of the OD theory.     

Protein-induced leakage and membrane destabilization of phosphatidylcholine and phosphatidylserine liposomes

By using spectroscopic and colloidal chemistry methods we studied the interactions of globular proteins with phospholipid membranes in relation to protein-promoted membrane fusion. We considered the effect of protein sorption on the destabilization of phosphatidylcholine and phosphatidylserine liposome membranes. Experimentally, we injected the proteins into fluorophore-quencher embedded liposome dispersions and recorded the leakage of fluorophore-quencher from the liposomes' inner compartment, which is due to the protein-induced destabilization of the phospholipid membranes. The release of fluorophore-quencher strongly depends on the protein concentration. The existence of monovalent and polyvalent cations also influences the protein-induced membrane destabilization by affecting the hydrophobic and electrostatic interactions.     

Infrared spectra and structure of carbanions—XIII: A study of the carbanions generated from acetonitrile,acetonitrile-d3 and acetonitrile-15n

The study of the IR spectral data for metallated acetonitrile (counter ions Li⁺, Na⁺, K⁺ in solvents tetrahydrofuran, THF, and hexamethylphosphotriamide, HMPT) and its D_3? and ¹⁵N- derivatives together with $\text{CNDO}\text{2}$ and normal coordinate calculations showed that the mesomeric ion H₂CCN has a favoured planar structure and the carbon-metal bond has a pronounced ionic character.     

Conversions of Coumarins Accompanied by Intermediate Opening and Recyclization of the Lactone Ring. 2. Study of the Interaction of Malonic Acid Hydrazide and Amide Derivatives with 3-Acyl(3-cyano, 3-ethoxycarbonyl)Coumarins

Reaction between the N,N′-diisopropylidene and N,N′-diacetyl derivatives of malonic acid dihydrazide and 3-acyl(3-cyano, 3-ethoxycarbonyl)coumarins under the conditions of the Michael reaction lead to the formation of N′-isopropylidene and N′-acetyl derivatives of coumarin-3-carboxylic acid hydrazide. Ethoxycarbonylacethydrazide reacts in an analogous manner. Special features have been studied of the interaction of malonic acid amide derivatives with unsubstituted coumarin and with coumarins containing electron-withdrawing groupings in position 3 of the ring. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1502–1514, October, 2005.     

Hydrogen-bonded complexes of nitrous and nitric acids with ethene Ab initio and DFT studies

The complexes formed by ethene with nitric and nitrous (trans and cis) acids have been investigated by ab initio (SCF and MP2) and B3LYP calculations with 6-311++G(d,p) basis set. Full geometry optimisation has been performed for the complexes studied. The most stable structures of the complexes are established. Bearing in mind the corrected values of the dissociation energy the studied hydrogen-bonded complexes can be ordered as follows: C(2)H(4)...HONO(2)>C(2)H(4)...HONO-trans>C(2)H(4)...HONO-cis. In the complexes the acids act as proton donors forming the pi-type of hydrogen bond with ethene. The predicted changes in the vibrational characteristics (vibrational frequencies and infrared intensities) arising from the hydrogen bonding are in good agreement with the experimentally measured. The predicted frequency shift of the stretching OH vibration in the nitric acid is largest (-210 cm(-1)), followed by the shifts in the trans-HONO (-141 cm(-1)) and cis-HONO (-109 cm(-1)). The calculations predict an increase of the IR intensity of the stretching O-H vibration in the complexes from 6 to 10 times.     

New Lead Silicates: Structures and Topology and Symmetry Analysis

Crystallography Reports - Crystals of a new complex layered lead carbonate silicate Pb19.4Na1.9[Si10O25](CO3)9(OH)12.7 ? 1.3H2O and lead silicogermanate...     

Generalized Arago–Fresnel laws: the EME-flow-line description

We study experimentally and theoretically the influence of light polarization on the interference patterns behind a diffracting grating. Different states of polarization and configurations are considered. The experiments are analyzed in terms of electromagnetic energy (EME) flow lines, which can be eventually identified with the paths followed by photons. This gives rise to a novel trajectory interpretation of the Arago–Fresnel laws for polarized light, which we compare with interpretations based on the concept of “which-way” (or “which-slit”) information.     

Theoretical study of the changes in the vibrational characteristics arising from the hydrogen bonding between Vitamin C (L-ascorbic acid) and H2O

The vibrational characteristics (vibrational frequencies, infrared intensities and Raman activities) for the hydrogen-bonded system of Vitamin C (L-ascorbic acid) with five water molecules have been predicted using ab initio SCF/6-31G(d,p) calculations and DFT (BLYP) calculations with 6-31G(d,p) and 6-31++G(d,p) basis sets. The changes in the vibrational characteristics from free monomers to a complex have been calculated. The ab initio and BLYP calculations show that the complexation between Vitamin C and five water molecules leads to large red shifts of the stretching vibrations for the monomer bonds involved in the hydrogen bonding and very strong increase in their IR intensity. The predicted frequency shifts for the stretching vibrations from Vitamin C taking part in the hydrogen bonding are up to -508 cm(-1). The magnitude of the wavenumber shifts is indicative of relatively strong OH...H hydrogen-bonded interactions. In the same time the IR intensity and Raman activity of these vibrations increase upon complexation. The IR intensity increases dramatically (up to 12 times) and Raman activity increases up to three times. The ab initio and BLYP calculations show, that the symmetric OH vibrations of water molecules are more sensitive to the complexation. The hydrogen bonding leads to very large red shifts of these vibrations and very strong increase in their IR intensity. The asymmetric OH stretching vibrations of water, free from hydrogen bonding are less sensitive to the complexation than the hydrogen-bonded symmetric OH stretching vibrations. The increases of the IR intensities for these vibrations are lower and red shifts are negligible.     

Crystallization,crystal-structure refinement,and IR spectroscopy of a synthetic hexahydroborite analog

The crystal structure of the hexahydroborite analog Ca[B(OH)₄]₂ · 2H₂O (a = 7.9941(3) Å, b = 6.6321(2) Å, c = 7.9871(3) Å, β = 104.166(4)°, V = 410.58(3) ų, sp. gr. P2/c, Z = 2, ρ_calc = 1.891 g/cm³; Xcalibur S CCD automated diffractometer, 1196 reflections with I > 2σ(I), λMoK _α), which was synthesized by the hydrothermal method via the recrystallization of calciborite CaB₂O₄ (M) in the M ? B₂O₃ ? H₂O system (t = 250°C and P = 70–80 atm), was refined by the least-squares method with anisotropic displacement parameters (H atoms were located; R ₁ = 0.0260). The structure of synthetic hexahydroborite consists of infinite columns running along the c axis. The columns are formed by Ca polyhedra linked together and to [B(OH)₄] orthotetrahedra by sharing edges. Along the two other axes, the translationally equivalent columns are linked only by hydrogen bonds. The presence of a stronger bond between the discrete (Ca-B-O) columns along the shortest (b = 6.6 Å) axis accounts for the possibility of the shift of the columns by 1/2T _b and the formation of the second modification of Ca[B(OH)₄]₂ · 2H₂O. The crystals of synthetic hexahydroborite were studied by IR spectroscopy. A crystal-chemical analysis was performed for a series of natural metaborates with the general formula CaB₂O₄ · nH₂O (CaO: B₂O₃ = 1: 1, n = 0–6), including calciborite CaB₂O₄ and hexahydroborite CaB₂O₄ · 6H₂O as the end members.