Synthesis and crystal structure of double Ln(III) malonates with Co(NH3) 6 3+ in the outer sphere

Double Ln(III) malonates of two different compositions crystallize from malonate solutions containing [Co(NH₃)₆]³⁺ ions. Lanthanides of the beginning of the series form compounds of the composition [Co(NH₃)₆][Ln(mal)₂]₃·6H₂O (I) (Ln = La, Ce, Pr, Nd; mal = C₃H₂O^2?), and those of the end of the series form compounds of the composition [Co(NH₃)₆]₂[Ln₃(mal)₇(Hmal)(H₂O)₄]·nH₂O (II) (Ln = Tb, Ho, Er, Tm). Structure I is based on trimeric anionic complexes [Ln₃(mal)₆]^3? linked with each other to form a branched 3D network with [Co(NH₃)₆]³⁺ cations and water molecules accommodated in large voids. The coordination mode of malonate ions in I with the coordination capacity equal to 5 was unknown previously for lanthanide malonate compounds. The Ln(1) atom has the maximum possible for malonate compounds coordination number (CN) 12, and the Ln(2) atom has CN 9. The structure of II consists of anionic chains [Ln₃(mal)₇(Hmal)(H₂O)₄] _n ^3? between which the [Co(NH₃)6]₃₊ cations and water molecules are arranged. One independent malonate ion in the structure is coordinated in the bidentate chelate fashion to the Ln(1) atom, and the other independent chelate-bridging ligand is coordinated in the bidentate fashion to the Ln(2) atom and in the monodentate fashion to the Ln(1) atom. As a result, tetrameric fragments linked in anionic chains are formed in the structure of II. The Ln(1) and Ln(2) atoms have CN 8.     

Synthesis and crystal structure of new Np(VI) and Pu(VI) phthalates, Na4{AnO2[(OOC)2C6H4]3} · n H2O

Double phthalates of Np(VI) and Pu(VI) of the composition Na₄[AnO₂L₃] · nH₂O [L = (OOC)₂C₆H₄] were synthesized in the crystalline form and studied by X-ray diffraction. The compounds are isostructural, their crystals consist of complex anions [AnO₂L₃]⁴⁻ and Na⁺ cations, forming neutral layers; water molecules are located between the layers. The coordination polyhedra of An(VI) are hexagonal bipyramids, whose average planes are formed by oxygen atoms of three phthalate anions. In passing from Np(VI) to Pu(VI), the actinide contraction is reflected to a greater extent in the variation of the bond lengths with apical oxygen atoms of the bipyramids, whereas the An-O bond lengths in the equatorial plane of the bipyramids vary insignificantly. Original Russian Text ? I.A. Charushnikova, N.N. Krot, I.N. Polyakova, Z.A. Starikova, 2007, published in Radiokhimiya, 2007, Vol. 49, No. 2, pp. 106–110.     

Self-heating of a coal bed under conditions of complicated access for air

The kinetics of the temperature conditions of a coal bed depending on the concentration of oxygen in coal was analyzed. The spatiotemporal dependence of the temperature and oxygen concentration in a coal bed was determined. It was found that oxygen penetrates into the bed to a limited depth; the presence of residual methane prevents the penetration of oxygen into the bed. It was demonstrated that, at limited access of oxygen to the bed, the temperature of the bed always achieves a specific stationary value unlike the case of a constant oxygen concentration, when conditions for an unlimited increase in the temperature can occur; a criterion for the appearance of these conditions was found. The stationary bed temperature was determined depending on the rate constant of sorption, bed voidage, residual methane pressure, bed thickness, coefficient of heat transfer to host rock, and flow rate of air from the headway to the bed.     

Continuously wavelength tuned optical parametric oscillator based on fan-out periodically poled lithium niobate

A PC-controlled optical parametric oscillator (OPO) based on fan-out periodically poled lithium niobate (MgO : PPLN) structures was developed. Continuous wavelength tuning (2.40–3.85 μm) was realized via linear displacements of fan-out MgO : PPLN structures using a PC-controlled precision motorized translation stage. The total wavelength scanning time in the range of 2.40–3.85 μm was ≤1 min. The OPO was developed as a source of tunable radiation for use in a laser photo-acoustic gas analyzer. Studies of the methane absorption spectrum showed a good coincidence of the experimental and theoretical data.     

A nanosecond optical parametric oscillator in the mid-IR region with double-pass pump

An optical parametric oscillator (OPO) with double-pass pump based on MgO:PPLN and PPLN periodic structures is described. A compact nanosecond Nd:YLF laser has been used as a pump source at 1.053 μm (the pumping pulse duration is 5–7 ns at a maximum pulse energy of 300 μJ at frequencies of 1–7 kHz). The oscillation threshold of the OPO based on MgO:PPLN was varied in a range of 11–28 μJ at wavelength of 2.1–4.3 μm. The conversion efficiency from the pump wave to an idler wave decreased from 8.6 to 2.5% in the range of 2.0–4.3 μm. For PPLN-OPO the measured threshold was 36 μJ at 4.2 μm and 49 μJ at 4.7 μm. The conversion efficiency of the pump energy into the energy of an idler wave was 3.3μ-0.4% at wavelengths of 4.2–4.7 μm.     

Synthesis,Crystal Structure,and Spectral Characteristics of the Np(V) Complex with Triphenylphosphine Oxide [NpO2(PO(C6H5)3)4]ClO4

Single crystals of [NpO₂(PO(C₆H₅)₃)₄]ClO₄ were grown and the structure of this compound was studied (CAD4 diffractometer, MoK ; triclinic unit cell: a = 9.140(2), b = 13.528(3), c = 13.918(3) Å, = 97.14(3)°, = 108.17(3)°, = 91.75(3)°, space group P-1, Z = 1, V = 1618.0 ų, d _{c a l c} = 1.521 g cm^-3; R ₁ = 0.0245 for 5342 observed reflections with F ₀ > 4(F ₀), wR ₂ = 0.0677 for 5601 unique reflections, 419 refined parameters). [NpO₂(PO(C₆H₅)₃)₄]ClO₄ consists of complex cations [NpO₂(PO(C₆H₅)₃)₄]⁺ and disordered ClO_4- anions. The Np(V) atom has tetragonal-bipyramidal oxygen surrounding with coordination number (CN) 6. The NpO₂ group is linear, the O = Np = O bond angle is 180.0°, and the Np = O bond length is 1.797(2) Å. The equatorial coordination plane of the bipyramid is formed by oxygen atoms of four triphenylphosphine oxide (TPPO) molecules. The Np-O_eq bond lengths vary from 2.434(2) to 2.442(2) Å (average 2.438 Å). The O_eq-Np-O_eq bond angle is close to the right angle (88.98°). The average bond lengths in TPPO ligands are P-O 1.498, P-C 1.798, and C-C 1.376 Å; the average bond angles are O-P-O 111.12°, C-P-C 107.78°, P-C-C 120.2, and C-C-C 120.0°. The electronic absorption spectra (Shimadzu UV-3100, 900-1050 nm) and IR spectra (Specord-M80, 400-4000 cm^{- 1}) of crystalline [NpO₂(PO(C₆H₅)₃)₄] were measured in an NaCl matrix. The absence of the main characteristic absorption band of the NpO₂ ⁺ dioxocation (980 nm) in the electronic absorption spectrum suggests centrosymmetrical equatorial surrounding of the Np(V) atom. The narrow absorption band ta_{a s}(NpO₂ ⁺) in the IR spectra in the region of 860 cm^-1 suggests the absence of cation-cation interaction, and its position is consistent with a short Np-O bond length in neptunyl(V) groups.     

Aryl[2.2]paracyclophane-Based Chiral Regioisomeric Analogs of Salicyl Aldehyde: Novel Sources for Construction of Phenoxy-Imine Ligands

The efficient, high-yield approaches to two novel regioisomeric salicyl aldehyde analogs, 4-formyl-13-(2-hydroxyphenyl)-[2.2]paracyclophane and 4-formyl-12-(2-hydroxyphenyl)-[2.2]paracyclophane ( iso -FHPhPC and pseudo -FHPhPC , respectively), constructed on the basis of an aryl[2.2]paracyclophane backbone are described. The key stage of the backbone formation is the Suzuki cross-coupling of paracyclophanyl halides with arylboronic acids. Efficient procedures for the resolution of the racemic hydroxy aldehydes into enantiomers via Schiff bases with enantiomers of α-phenylethyl amine were elaborated, and the absolute configurations of enantiomers were established on the basis of X-ray analysis of diastereomeric imines. Starting from these chiral hydroxy aldehydes the first representatives of bi-, tri-, and tetradentate phenoxy-imine ligands belonging to an aryl[2.2]paracyclophane family were obtained. The induction power of the ligands was tested in the Et₂Zn asymmetric addition to aldehydes.