Refinement of the angular dependence of the peptide vicinal NHCαH coupling constant

The refined dependence of the peptide NHCαH vicinal coupling constant on the dihedral angle θ have been derived on the basis of the accumulated experimental data. The mean permissible values (in Hz) are approximated by ³J_NHCH = 9·4 cos² θ - 1·1 cos θ + 0·4 An analogous relationship for the sum of two vicinal NHCαH₂ coupling constants in the glycyl residue have been calculated from the above dependence. Measurements on N-methylacetamide in various solvents and in the presence of an alkali salt showed the vicinal constant NHCH to vary by not more than ± 3%. Some of the other proposed ³J_NHCH(θ) dependencies give too low values for the cis-oriented NH and CαH bonds. This may be due to the fact that in these correlations the data for compounds with cis-amide bonds have been used for 0° ? θ ? 90° region of the dependence.     

Acoustic and dielectric anomalies in the temperature range of a ferroelectric phase transition in glycine phosphite crystals

The acoustical and dielectric properties of glycine phosphite crystals are investigated in the temperature range of a ferroelectric phase transition. The acoustic anomalies for longitudinal waves along the X, Y, and Z crystallographic axes (where Y is the spontaneous polarization axis) are analyzed in the framework of the Landau theory. It is shown that pronounced acoustic anomalies of the velocity can be quantitatively described within the pseudoproper ferroelectric phase transition model with due regard for the long-range dipole-dipole interaction. For longitudinal acoustic waves propagating along the polar crystal axis, the striction anomaly of the velocity is only partly suppressed by the long-range dipole-dipole forces and an abrupt jump in the velocity is observed in the vicinity of the phase transition. The temperature coefficients of the velocity in the paraphase are determined. The striction contribution and the contributions biquadratic in the order parameter and in the strain to the velocity anomaly are separated.     

Synthesis and Luminescent Properties of Lanthanide Complexes with Benzothiazolylphenolate and -Naphtholate Ligands

Russian Journal of Coordination Chemistry - Sm, Er, and Yb complexes containing anionic (4,5,6,7-tetrafluorobenzothiazol-2-yl)-2-(3,4,5,6-tetrafluoro)phenolate (SONF) and...     

Synthesis,structure, and luminescence properties of sodium and ytterbium complexes with 2-(benzothiazol-2-yl)selenophenolate ligands

Russian Chemical Bulletin - With the aim of designing new heteroorganic ligands capable of sensitizing the metal-centered photoluminescence (PL) of YbIII through the redox mechanism, a new...     

On Fredholm Solvability of the Dirichet Problem for Linear Differential Equations of Infinite Order

We propose a new approach to investigation of solvability of the Dirichlet problem for differential equations of infinite order. Namely, by using the embedding theorems obtained by the author in previous papers for the energy spaces, corresponding to operators of infinite order, the initial differential operator of infinite order is expressed as a sum of the main and subordinate operators of infinite order. The conditions, under which the above Dirichlet problems are soluble, are established by using the main term of the corresponding differential operator.     

The experimental and computer studies of the double-scattering effect for polycrystals

The effect of double scattering of 10–35 keV Ar ions by a copper polycrystal has been studied in the case of asymmetric reflection. Contributions from collisions of various multiplicities to the obtained energy spectra have been analysed theoretically. The spectra are computer-calculated using the statistical trial method with due account for a discrete set of possible distances between the surface atoms which scatter the ions. The charge-exchange processes are also included in the calculations.     

Lanthanide complexes with the Schiff base containing sterically hindered phenol: Synthesis,structure, and luminescence properties

The syntheses of the 2,6-di-tert-butyl-4-(2-hydroxybenzylideneamino)phenolate (L) complexes of Gd (I), Nd (II), Er (III), Yb (IV), Tm (V), Sm (VI), and Tb (VII) are described. The structures of the Gd and Er complexes are determined by X-ray diffraction analysis (CIF files CCDC nos. 1558820 (I) and 1558819 (III)). All synthesized compounds exhibit ligand-centered photoluminescence in a range of 405–485 nm. In addition, the luminescence spectra of solid samples of the neodymium and ytterbium complexes contain narrow bands of f–f transitions characteristic of Nd³⁺ and Yb³⁺ ions.     

ate complexes of lanthanides with aryloxide ligands: Synthesis, structures, and luminescence properties

(2-Benzox(thi)azol-2-yl)phenolate and -naphtholate ate complexes of Sc, Y, La, Sm, Tb, and Yb are synthesized. The structure of (benzoxazolyl)phenolate complexes of La, Sm, and Yb are determined by X-ray diffraction analysis. All synthesized compounds manifest ligand-centered photo- and electroluminescence in a range of 510–540 nm. In addition, the spectra of the samarium and terbium complexes exhibit narrow bands of f-f transitions characteristic of Sm³⁺ and Tb³⁺ ions.