Ferromagnetic versus antiferromagnetic exchange interactions in tetrathiafulvalene-based 3d/4f heterobimetallic complexes

(TTF-salphen)M compounds (TTF-salphen(2-)=4,5-bis(propylthio)tetrathiafulvalene-N,N'-phenylenebis(salicylideneimine) dianion; M=Cu(II) and Ni(II)) have been treated with Ln(hfac)(3)·2H(2)O precursors (hfac(-)=1,1,1,5,5,5-hexafluoroacetylacetonate anion; Ln=Gd(III), Tb(III), and Dy(III)) to elaborate unprecedented 3d/4f TTF-based heterobimetallic complexes of formula [(TTF-salphen)MLn(hfac)(3)]. All the structures of these compounds have been resolved by X-ray diffraction on single crystals. The structures of these complexes are formed by a TTF-salphen(2-) ligand coordinated to the 3d metal ions in the inert tetradentate N(2)O(2) site. The Ln(hfac)(3) fragment is coordinated to the (TTF-salphen)M one through the two phenolate bridges. Even if the complexes are similar in both Cu(II) and Ni(II) families, the crystal packing is different. In the first case, dimers of TTF-salphen(2-) donors constitute the organic network. In the other case, a reminiscent organic network is observed with S···S contacts. The photophysical properties of [(TTF-salphen)CuDy(hfac)(3)] (3) in chloroform solution highlight the redshift of the TTF→salphen charge transfer (400 cm(-1)) relative to the analogue excitations in (TTF-salphen)Cu, which attest to the stability of these structures in solution. Static magnetic measurements have allowed us to quantify the ferromagnetic interactions (J=+1.29 cm(-1)) between Cu(II) and Gd(III) in the [(TTF-salphen)CuGd(hfac)(3)] complex. Finally, an empirical method that consists of the comparisons of the magnetic properties of [(TTF-salphen)CuTb(hfac)(3)] with [(TTF-salphen)NiTb(hfac)(3)] and [(TTF-salphen)CuDy(hfac)(3)] with [(TTF-salphen)NiDy(hfac)(3)] has established that ferromagnetic interactions take place between Cu(II) and Tb(III) ions, whereas unusual antiferromagnetic interactions have been identified between Cu(II) and Dy(III) ions.     

Modeling of the molecular and electronic structures of some mono- and biosmium complexes of fullerene C60

The modeling of the molecular and electronic structures of the following mono- and biosmium complexes of fullerene C₆₀ was performed by quantum chemical methods (MNDO/PM3 and DFT/PBE): (??²-C₆₀)[Os(PPh₃)₂(CO)CNMe], (??²,??²-C₆₀)[Os(PPh₃)₂(CO)(CNMe)]₂, (??²-C₆₀)[Os(PH₃)₂(CO)H], (??²,??²-C₆₀)[Os(PH₃)₂(CO)H]₂, (??²-C₆₀)[Os(PH₃)₂(CO)CNMe], (??²,??²-C₆₀)[Os(PH₃)₂(CO)CNMe]₂, and (5-C₆₀H₅)[Os(C₅H₅)], (5, 5-C₆₀H₁₀)[Os(C₅H₅)]₂.The osmium atoms in the first six complexes are ??²-coordinated by fullerene C₆₀. In the last two complexes, the ??⁵-coordination mode is observed. The structures of the radical anions of these complexes were calculated. The energies of the frontier orbitals were evaluated. The acceptor properties of the complexes are discussed. The electron affinities were estimated in two ways: from the energy of the lowest unoccupied molecular orbital (LUMO) and as the energy difference between the neutral molecule and its radical anion.     

Stability of anisotropic electroactive polymers with application to layered media

The stability of anisotropic electroactive polymers is investigated. A general criterion for the onset of instabilities under plane-strain conditions is introduced in terms of a sextic polynomial whose coefficients depend on the instantaneous electroelastic moduli. In a way of an example, the stable domains of layered neo-Hookean dielectrics are determined. It is found that depending on the direction of the electrostatic excitation field relative to the lamination direction, the critical stretch ratios at which instabilities may occur can be either larger or smaller than the ones for the purely mechanical case.     

Quantitative estimates for a new complex Durrmeyer operator in compact disks

In the recent years the extension of linear positive operators from real to complex domain is one of the interesting area of research. In this context, we present the exact order of simultaneous approximation and Voronovskaja kind results with quantitative estimate for a new type of complex Durrmeyer operator (different from those previously studied), attached to analytic functions in compact disks. In this way, we put in evidence the overconvergence phenomenon for this kind of Durrmeyer operator, namely the extensions of approximation properties with exact quantitative estimates, from the real interval [1/3, 2/3] to compact disks in the complex plane.     

Selected bibliography on degeneracy

A selected bibliography on degeneracy problems organized according to the appearance of the respective references in various fields of operations research is given.     

n-Dimensional hyperbolic complex numbers

Direct product rings have received relatively little attention, perhaps because they are sometimes labeled “trivial” [8, p.6]. Nevertheless, the 2-dimensional direct product ring of the reals, when expressed in the “hyperbolic basis”, is analogous in many ways to the system of complex numbers and also has a physical interpretation. This prompted an exploratory foray into the world ofn-dimensional direct product rings of the reals to see how much can be extended from the 2-dimensional case (see, e.g. [3,4,5]). Section 1 provides algebraic notation, up to the point of defining polar coordinates. Section 2 uses analysis to explore differentiability and conformality.     

Study of the pumping-radiation-absorption effect on the generation efficiency of solutions of complex organic compounds

Using the method of mathematical simulation, we calculate the energy efficiency of the generation of 1,4-di[2-(5-phenyloxazolile)] benzene solutions in dioxane with allowance for the reabsorption of pumping radiation in a system of excited singlet states. The results of calculation agree with experimental data. Deceased. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 744–747, November–December, 1997.     

Synthesis and characterization of fluorene‐based low‐band gap copolymers containing propylenedioxythiophene and benzothiadiazole derivatives for bulk heterojunction photovoltaic cell applications

The following noble series of soluble π‐conjugated statistical copolymers was synthesized by palladium catalyzed Suzuki polymerization: poly[(9,9‐dioctylfluorene)‐alt‐(4,7‐bis(3′,3′‐dihepyl‐3,4‐propylenedioxythienyl)‐2,1,3‐benzothiadiazole)] (PFO‐PTBT) derived from poly(9,9‐dioctylfluorene) (PFO) and poly[(4,7‐bis(3′,3′‐dihepyl‐3,4‐propylenedioxythienyl)‐2,1,3‐benzothiadiazole)] poly(heptyl₄‐PTBT). The structure and properties of these polymers were characterized using ¹H‐, ¹³C‐NMR, UV–visible spectroscopy, elemental analysis, GPC, DSC, TGA, photoluminescence (PL), and cyclic voltammetry (CV). The statistical copolymers, PFO‐PTBT (9:1, 8.4:1.6, 6.5:3.5), were soluble in common organic solvents and easily spin coated onto indium‐tin oxide (ITO) coated glass substrates. The weight‐average molecular weight (M_w) and polydispersity of the PFO‐PTBT ranged from (1.0–4.2) × 10⁴ and 1.5–2.3, respectively. Bulk heterojunction photovoltaic cells with an ITO/PEDOT/PFO‐PTBT:PCBM/LiF/Al configuration were fabricated, and the devices using PFOPTBT (6.5:3.5) showed the best performance compared with those using PFO‐PTBT (9:1, 8.4:1.6). A maximum power conversion efficiency (PCE) of 0.50% (V_oc = 0.66 V, FF = 0.29) was achieved with PFO‐PTBT (6.5:3.5). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6175–6184, 2008     

Multistep contributions to 13C(π+, π°)13N within a modified eikonal formalism

Analog (π⁺, π⁰) charge exchange on ¹³C in the (3, 3) resonance region is considered within a modified eikonal formalism, which makes use of traditional eikonalization only for pion-nuclear processes, but not for pion-nucleon processes. Corrections to DWIA, based on two-step processes as suggested by Eisenberg and Gal are evaluated. The calculated charge exchange total cross section is found to increase due to these corrections by 15 %, and is still well below the measured one for T_π > 150 MeV.