Quantum-chemical study,IR spectra,and intramolecular hydrogen bonds in dimeric 5- and 6-methyluracils

Comparative analysis of the geometry, atomic charges, force constants, and IR spectra of crystals of isomeric 5- and 6-methyluracils was performed by quantum-chemical methods. Dimeric and trimeric associates of C-methyluracil molecules and their dimers with adenine were calculated in order to estimate the energies of intramolecular hydrogen bonds. Thymine in DNA is impossible to replace by 6-methyluracillargely by steric reasons.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 12, 2004, pp. 2038–2047.Original Russian Text Copyright © 2004 by Naumov, Tafipolskii, Reznik.This revised version was published online in April 2005 with a corrected cover date.     

Unexpected formation of a novel macrocyclic tetraphosphine: (RSSR)-1,9-dibenzyl-3,7,11,15-tetramesityl-1,9-diaza-3,7,11,15-tetraphosphacyclohexadecane

The title compound was synthesised in moderate yield via stereoselective self-assembly of two bisphosphine, four formaldehyde and two primary amine molecules.     

Investigation of the anisotropy of the properties of glass-reinforced plastic shells

The load-carrying capacity and deformation of cylindrical and conical glass-reinforced plastic (ÉDT-10 resin) shells loaded in axial compression have been investigated experimentally in relation to the orientation of the fabric reinforcement. The results of the tests are compared with the relations of the theory of elasticity of an orthotropic body.Zhukovskii Central Aerohydrodynamics Institute, Moscow Region; Scientific Research Institute of Production Technology and Organization, Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 814–818, September–October, 1969.     

The effect of alkyl chain length on the thermodynamic properties of the half esters of o-phthalic acid

The temperature, heat and entropy of fusion of four half esters of o-phthalic acid have been measured. These values are compared to other aromatic acid properties on the basis of molecular weight. The calorimetric data have an accuracy of ±5% and agree well with values predicted from simple entropy, geometric and electronic considerations.     

Optical and gain properties of series of crystals LiF-YF3-LuF3 doped with Ce and Yb ions

Here, we present first results of systematic studies of host cation variation impact on spectral-kinetic, photochemical and gain properties of Ce³⁺-doped LiYF₄ (YLF), LiLuF₄ (LLF) and LiY_1−xLu_xF₄ family crystals. 5d-4f luminescence decay of Ce³⁺ ions studies, together with pump-probe experiments, indicate that previously reported twice higher luminescence quantum yield in LLF compared with that of YLF crystals is provided by more efficient upper lasing level feeding due to recombination and higher color center destruction rate in LLF against YLF crystals. Namely, it is responsible for higher energetic characteristics of laser based on Ce³⁺:LLF crystals. Strong and wide pump-induced absorption band centered at 310 nm is observed in Ce³⁺:YLF. This band is shifted to blue and its intensity goes down with Lu content. We have evaluated free charges recombination rate, excited state absorption cross-section for Ce³⁺ ions and some other photodynamic processes related microparameters. Fitting results indicate that pump-induced color centers lifetime decreases with Lu-content in LiYF₄-LiLuF₄ mixture and it can be associated with more efficient color center bleaching by Ce³⁺ ions 5d-4f fluorescence.     

Phase transformations in CuO caused by bombardment by He<Superscript>+</Superscript> ions and by the action of spherical shock waves

The valence state of copper ions and the phase composition of copper monoxide CuO subjected to bombardment by He⁺ ions and explosive shock waves are studied by the methods of x-ray photoelectron spectroscopy (XPS) and x-ray emission spectroscopy (XES). Measurements of photoelectron Cu 2p and emission O K_α spectra revealed a decrease in the concentration of Cu²⁺ ions and partial reduction of CuO to Cu₂O as a result of both ion bombardment and shock-wave loading. The concentration of the Cu₂O phase attained values of 10–15%. The Cu₂O phase is revealed by the XPS and XES methods even at concentrations lower than its threshold concentration for detection by x-ray diffraction measurements. This points to the effectiveness of XPS and XES techniques in studying nanocrystalline materials and defect structures containing finely dispersed inclusions. A model for the emergence of Cu₂O due to the formation of charged clusters under the action of stress waves is proposed.     

Synthesis and structures of Cu<Superscript>I,II</Superscript> complexes with a 2,2´-bipyridine derivative bearing a (+)-3-carene moiety

The complex salt {[CuL₂][Cu₄I₆]?MeCN}_n (1) and the compound [Cu₄L₃I₄]?3 MeCN (2) (L is a chiral ligand bearing a natural monoterpene (+)-3-carene moiety) were synthesized. The crystal structures of compounds 1 and 2 were determined by X-ray diffraction. The structure of compound 1 consists of complex cations [CuL₂]²⁺ (N₃O₂ polyhedron is a trigonal bipyramid) and Cu^I coordination polymers (CuI₄ polyhedron is a tetrahedron) as anions. The experimental magnetic moment μ_eff at 300 K is 1.90 μ_B, which is consistent with the X-ray diffraction data and the assumption that compound 1 is mixed-valence. The structure of compound 2 comprises a tetranuclear Cu^I complex, in which three Cu atoms are coordinated by two N atoms of the ligand L and two I atoms, and the fourth Cu atom is coordinated by four I atoms (coordination polyhedra are distorted tetrahedra). Compounds L and 2 were found to influence the viability of human laryngeal carcinoma cells (Hep2). The IC₅₀ value for complex 2 (13.0±1.7 μM) is substantially smaller than IC₅₀ for compound L (30.5±0.5 μM).     

Synthesis and Physicochemical Study of Iron(II), Cobalt(II), Nickel(II), and Copper(II) Complexes with 4-(2-Pyridyl)-1,2,4-Triazole

New complexes of iron(II), cobalt(II), and nickel(II) with 4-(2-pyridyl)-1,2,4-triazole (PyTrz), [Fe₃(PyTrz)₈(H₂O)₄]A₆ (A = NO₃ ^-, ClO₄ ^-, Br^-) and [M₃(PyTrz)₈(H₂O)₄](NO₃)₆ (M = Co, Ni), were synthesized and studied by X-ray diffraction, magnetochemical method, and electronic and IR spectroscopy. The complex [Fe₃(PyTrz)₈(H₂O)₄](NO₃)₆) was also studied by adiabatic calorimetry. The Fe(II), Co(II), and Ni(II) nitrate complexes were shown to be isostructural to the previously synthesized linear trinuclear [Cu₃(PyTrz)₈H₂O)₄](NO₃)₆ complex. In all compounds, antiferromagnetic exchange interactions between M²⁺ ions were detected. The complex [Fe₃(PyTrz)₈(H₂O)₄](NO₃)₆ undergoes the ¹ A ₁ ⁵ T ₂ spin transition.