Synthesis and Photophysical Properties of α-(N-Biphenyl)-Substituted 2,2′-Bipyridine-Based Push–Pull Fluorophores

A series of new α-(N-biphenyl)-substituted 2,2′-bipyridines were obtained through the combination of the ipso-nucleophilic aromatic substitution of the C5-cyano group, aza-Diels–Alder and Suzuki cross-coupling reactions, starting from 5-cyano-1,2,4-triazines. For the obtained compounds, photophysical and fluorosolvatochromic properties were studied. Fluorophores 3l and 3b demonstrated unexpected AIEE activity, while 3a and 3h showed promising nitroexplosive detection abilities.     

Morphology- and phase-controlled iron oxide nanoparticles stabilized with maleic anhydride grafted polypropylene

About phase: Ferromagnetic γ-Fe(2) O(3) nanowires (left in the figure) with a saturation magnetization (M(s) ) of 54.0?emu?g(-1) and coercivity of 518?Oe at room temperature, and superparamagnetic hollow α-Fe(2) O(3) nanoparticles (right) with a room-temperature M(s) of 2.9?emu?g(-1) were synthesized by the thermal decomposition of [Fe(CO)(5) ] but with the stabilizing action of maleic anhydride grafted polypropylene.     

New molecular magnetic metals: κ-(BDH-TTP)4CuCl4·(H2O)n and κ-(BDH-TTP)2[CuCl4]0.67·(H2O)0.33 (BDH-TTP is 2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene)

New radical cation salts based on 2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene (BDH-TTP), viz., κ-(BDH-TTP)₄CuCl₄·(H₂O) _n (1) and κ-(BDH-TTP)₂[CuCl₄]_0.67· ·(H₂O)_0.33 (2), were synthesized and structurally characterized. Single crystals were prepared by the electrochemical oxidation of BDH-TTP under galvanostatic conditions. The X-ray diffraction study showed that the salts have layered structures characterized by the presence of κ-type BDH-TTP conducting layers. These layers alternate with the complex anions composed of [CuCl₄]²⁻ units and water molecules. Both salts exhibit the temperature dependence of the metallic conductivity down to 4.2 K. Spin-spin antiferromagnetic correlations in the Cu²⁺ subsystem were observed in the crystals of 2.     

Integration of the sine-Gordon equation with a self-consistent source of the integral type in the case of multiple eigenvalues

The paper is dedicated to the evolution of the scattering data for a Dirac-type nonself-adjoint operator with multiple eigenvalues whose potential is a solution of the sine-Gordon equation with a self-consistent source of the integral type.     

Negatively charged pi-(C60-)2 dimer with biradical state at room temperature

A negatively charged pi-(C60-)2 dimer bonded by two single bonds was found in the ionic multicomponent complex {(MDABCO+).CoIITMPP}2.(C60-)2.(C6H4Cl2)2.5.(C6H5CN)1.5 (1). In contrast to the previously described diamagnetic sigma-(C60-)2 dimer, the negatively charged pi-dimer has a biradical state at room temperature: (C60*-)2 (S = 1). The behavior of spins in this dimer can be described by a model with a singlet ground state (S = 0) and a close lying excited triplet (S = 1) state with the energy gap of 2|JAF| = 70 +/- 2 cm-1. On the whole, complex 1 shows a strong antiferromagnetic interaction of spins with a Weiss constant of -34 K.     

The Korteweg-de Vries equation with a self-consistent source in the class of periodic functions

We use the inverse spectral problem method to integrate the Korteweg-de Vries equation with a self-consistent source in the class of periodic functions.     

Structural aspects of two-stage dimerization in an ionic C60 complex with bis(benzene)chromium: Cr(C6H6)2.C60.C6H4Cl2

Single crystals of the ionic C60 complex with bis(benzene)chromium: {Cr(I)(C6H6)2(.+)}.(C60.-)).C6H4Cl2 (1) were obtained. The crystal structure of 1 shows the presence of monomeric C60.- radical anions at 250 K and the formation of single-bonded (C60-)2 dimers at 90 K. The dimerization is realized in two types of the C60.-) pairs with different interfullerene center-to-center distances of 10.052 and 10.279 A arranged in zigzag chains along the a-direction. As a result, two symmetrically independent (C60-)2 dimers found in 1 at 90 K have different environments, intercage C-C bond lengths and C60- center-to-center distances. Such differences should provide different thermal stability of these dimers and result in the appearance of two stages at the dimerization. Indeed, according to SQUID measurements, the magnetic moment of 1 decreases stepwise at the dimerization in two temperature ranges at 240-200 and 200-160 K.     

A Mössbauer investigation of zirconium distribution and diffusion in ball milled nanocrystalline iron powders

Ball milled nanocrystalline iron with minor zirconium additions was examined using ⁵⁷Fe Mössbauer spectroscopy and X-ray diffraction. Powder samples were synthesized using 0, 5, and 10 wt.% zirconium additions and milled at room temperature for periods up to 24 h. Progressive decrease in grain size as determined by X-ray diffraction was observed as a function of milling time. Mössbauer spectroscopy indicates increased iron-zirconium coordination with increased milling time. After milling, the powder samples were then heat treated in an inert atmosphere of argon at up to 925 K for various times up to 25 min. Analysis of X-ray peak line width (FWHM) was used to characterize grain size and grain growth kinetics as a function of heat treatment, milling time, and alloy content and reveal an increasingly finer post-heated structure in the alloy samples containing more zirconium. Mössbauer measurements were made and suggest Zr is steadily distributed into the Fe lattice with milling and rapidly diffuses to the grain boundaries with heat treatment. The impurity-rich grain boundaries appear to considerably stabilize the refined structure.     

Radical Cation Salts of Tetrathiotetracene and Tetraselenotetracene with Photochromic Anion [Fe(NO)(CN)5]2–

Radical cation salts of tetrathiotetracene (TTT) and tetraselenotetracene (TSeT) with photochromic anion [Fe(NO)(CN)₅]^2– having the compositions (TTT)₃[Fe(NO)(CN)₅] (I) and (TSeT)₃[Fe(NO)(CN)₅] (II) were synthesized. Their crystal structures and conducting and optical properties were studied. The salt structures are featured by stacks of TTT or TSeT triads. Analysis of the bond lengths in TTT and TSeT revealed localization of a charge in the triads, where one molecule is neutral and the other two molecules are charged (1+). At room temperature, the conductivity of crystals I and II along the stack direction is 6 × 10^–2 and 5–7 Ohm^–1 cm^–1, respectively. Unlike I, the temperature dependence of conductivity of II has peculiarities at 285 and 160 K due to phase transitions. The transition at 160 K was discovered also in the reflection spectra.