Preparation and properties of monoorganoantimony tetrachloride adducts

Several adducts of monoorganoantimony tetrachlorides, RSbCl₄L (R = CH₃, C₆H₅, p-CH₃C₆H₄; L = HMPT, PyO, 4-CH₃PyO, DMSO), were prepared. In the solid state all of these adducts are stable at room temperature. They are monomeric in solution, and the existence of hexacoordinate antimony is indicated. CH₃SbCl₄L (L = PyO, 4-CH₃PyO) exists in two isomeric forms in solution and decomposes above 70° into CH₃Cl and SbCl₃L. CH₃SbCl₄(HMPT) decomposes in a similar manner even at room temperature.     

Anionic NaCl-type frameworks of [Mn(II)(HCOO)(3)(-)], templated by alkylammonium, exhibit weak ferromagnetism

We present the synthesis, characterization by IR, TGA, single crystal X-ray structure and magnetic properties of a novel series of NaCl-type frameworks of [AmineH(+)][Mn(HCOO)(3)(-)], templated by alkylammonium. The anionic NaCl-framework of [Mn(HCOO)(3)(-)] is counter-balanced by the alkylammonium cations located in the cavities of the framework to which they are hydrogen-bonded. The divalent manganese ions have octahedral geometry and are bridged by the formate in an anti-anti mode of coordination. All the compounds exhibit long-range antiferromagnetism below 9 K with a slight non-collinear arrangement of the moments. The canting, likely due to second-order spin-orbit coupling, is via a Dzyaloshinski-Moriya antisymmetric exchange mechanism. A spin-flop is observed in each case at fairly low fields. An orthorhombic to monoclinic transformation was observed for the protonated cyclotrimethyleneamine that is accompanied by localization of the cations into two positions below 240 K from the rapid dynamic flipping of the ring observed at room temperature.     

Self-assembly of oligothiophene chromophores by m-calix[3]amide scaffold

m-Calix[3]amides carrying the bithiophene chromophore (BTC3A) and terthiophene chromophore (TTC3A) were synthesized by the cyclic trimerization of m-aminobenzoic acid esters for the purpose of the control and understanding of the self-assembly of oligothiophene chromophores. Polymers and model compounds were also prepared for comparison. From the (1)H NMR experiments, cyclic trimer BTC3A showed the syn/anti equilibrium in solution, and the syn/anti conformer ratio (76/24 in CDCl(3)) was influenced by the solvent character. Namely, the population of the syn conformer was lowest (70%) in THF-d(8) and was highest (86%) in CDCl(3)/CD(3)OD (1/1 in volume). On the other hand, the population of the syn conformer of cyclic trimer TTC3A was high (84%) even in CDCl(3). In a CHCl(3) solution of cyclic trimer BTC3A, the absorption maximum (342 nm) blue-shifted and the emission maximum (448 nm) red-shifted compared with those of polymer BTPA and model compound BTM. The solvent character also had an impact on the optical properties of cyclic trimer BTC3A. The red-shifted emission maximum (481 nm) of cyclic trimer BTC3A in CH(3)OH indicated the interaction between three bithiophene chromophores. The emission maxima of cyclic trimer TTC3A (486 nm) demonstrated a small red-shift from model compound TTM (477 nm), and no solvent dependency was observed, unlike cyclic trimer BTC3A.     

Iridoid and acyclic monoterpene glycosides, kankanosides L, M, N, O, and P from Cistanche tubulosa

Three iridoid glycosides, kankanosides L, M, and N, and two acyclic monoterpene glycosides, kankanosides O and P, were isolated from fresh stems of Cistanche tubulosa (Orobanchaceae) together with eight iridoid glycosides, five acyclic monoterpene glycosides, three phenylpropanoid glycosides, and four lignan glycosides. Their structures were elucidated on the basis of chemical and physicochemical evidence.     

Dynamics of femtosecond-laser-ablated liquid-aluminum nanoparticles probed by means of spatiotemporally resolved X-ray absorption spectroscopy

We investigated spatiotemporal evolution of expanding ablation plume of aluminum created by a 100-fs, 10¹⁴–10¹⁵-W/cm² laser pulse. For diagnosing dynamic behavior of ablation plume, we employed the spatiotemporally resolved X-ray absorption spectroscopy (XAS) system that consists of a femtosecond-laser-plasma soft X-ray source and a Kirkpatrick–Baez (K–B) microscope. We successfully assigned the ejected particles by analyzing structure of absorption spectra near the L _II,III absorption edge of Al, and we clarified the spatial distribution of Al⁺ ions, Al atoms, and liquid droplets of Al in the plume. We found that the ejected particles strongly depend the irradiated laser intensity. The spatial distribution of atomic density and the expansion velocity of each type of particle were estimated from the spatiotemporal evolution of ablation particles. We also investigated a temperature of the aluminum fine particles in liquid phase during the plume expansion by analyzing the slope of the L _II,III absorption edge in case of 10¹⁴-W/cm² laser irradiation where the nanoparticles are most efficiently produced. The result suggests that the ejected particles travel in a vacuum as a liquid phase with a temperature of about 2500 to 4200 K in the early stage of plume expansion.     

Finite sheeted covering maps over 2-dimensional connected, compact Abelian groups

Let G be a 2-dimensional connected, compact Abelian group and s be a positive integer. We prove that a classification of s-sheeted covering maps over G is reduced to a classification of s-index torsionfree supergroups of the Pontrjagin dual . Using group theoretic results from earlier paper we demonstrate its consequences. We also prove that for a connected compact group Y:

(1)

Every finite-sheeted covering map from a connected space over Y is equivalent to a covering homomorphism from a compact, connected group.

(2)

If two finite-sheeted covering homomorphisms over Y are equivalent, then they are equivalent as topological homomorphisms.

     

Zero distribution and division results for exponential polynomials

An exponential polynomial of order q is an entire function of the form

$$g(z) = {P_1}(z){e^{{Q_1}(z)}} + ...{P_k}(z){e^{{Q_k}(z)}},$$

where the coefficients P_j(z),Q_j(z) are polynomials in z such that

$$\max \{ deg({Q_j})\} = q.$$

It is known that the majority of the zeros of a given exponential polynomial are in domains surrounding finitely many critical rays. The shape of these domains is refined by showing that in many cases the domains can approach the critical rays asymptotically. Further, it is known that the zeros of an exponential polynomial are always of bounded multiplicity. A new sufficient condition for the majority of zeros to be simple is found. Finally, a division result for a quotient of two exponential polynomials is proved, generalizing a 1929 result by Ritt in the case q = 1 with constant coefficients. Ritt’s result is closely related to Shapiro’s conjecture that has remained open since 1958.

     

Luminescence tuning of imidazole-based lanthanide(III) complexes [Ln = Sm, Eu, Gd, Tb, Dy

To tune the lanthanide luminescence in related molecular structures, we synthesized and characterized a series of lanthanide complexes with imidazole-based ligands: two tripodal ligands, tris{[2-{(1-methylimidazol-2-yl)methylidene}amino]ethyl}amine (Me(3)L), and tris{[2-{(imidazol-4-yl)methylidene}amino]ethyl}amine (H(3)L), and the dipodal ligand bis{[2-{(imidazol-4-yl)methylidene}amino]ethyl}amine (H(2)L). The general formulas are [Ln(Me(3)L)(H(2)O)(2)](NO(3))(3)·3H(2)O (Ln = 3+ lanthanide ion: Sm (1), Eu (2), Gd (3), Tb (4), and Dy (5)), [Ln(H(3)L)(NO(3))](NO(3))(2)·MeOH (Ln(3+) = Sm (6), Eu (7), Gd (8), Tb (9), and Dy (10)), and [Ln(H(2)L)(NO(3))(2)(MeOH)](NO(3))·MeOH (Ln(3+) = Sm (11), Eu (12), Gd (13), Tb (14), and Dy (15)). Each lanthanide ion is 9-coordinate in the complexes with the Me(3)L and H(3)L ligands and 10-coordinate in the complexes with the H(2)L ligand, in which counter anion and solvent molecules are also coordinated. The complexes show a screw arrangement of ligands around the lanthanide ions, and their enantiomorphs form racemate crystals. Luminescence studies have been carried out on the solid and solution-state samples. The triplet energy levels of Me(3)L, H(3)L, and H(2)L are 21?000, 22?700, and 23?000 cm(-1), respectively, which were determined from the phosphorescence spectra of their Gd(3+) complexes. The Me(3)L ligand is an effective sensitizer for Sm(3+) and Eu(3+) ions. Efficient luminescence of Sm(3+), Eu(3+), Tb(3+), and Dy(3+) ions was observed in complexes with the H(3)L and H(2)L ligands. Ligand modification by changing imidazole groups alters their triplet energy, and results in different sensitizing ability towards lanthanide ions.