An anhydrous copper carboxylate compound of formula [Cu(trans-2-butenoate)(2)](n) has been characterized. X-ray analysis reveals a structure built by paddlewheel units bridged by pairs of Cu...O axial bonds to give infinite chains arranged in a new topological motif. Susceptibility measurements in the 10-300 K temperature range, and isothermal magnetization curves at 2, 5, 10, and 50 K with fields up to 5 T, were obtained. Electron Paramagnetic Resonance (EPR) spectra of powder samples were measured at 33.9 GHz at 300 K, and at 9.60 GHz at temperatures in the range 90

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This study consisted of an investigation of the thermo-mechanical properties of post-consumer high impact polystyrene (HIPS) through five consecutive injection moulding steps to simulating the recycling cycles. The selectively collected HIPS residue was ground, washed only in water, dried, agglutinated and then moulded as a set of mechanical test specimens before the first step. The melt flow index (MFI), glass transition temperature (Tg), complex viscosity (η*), deflection temperature under flexural load (HDT), tensile, flexural and impact strength tests were determined at each reprocessing cycles. The results revealed that the degradative effect of consecutive recycling on the material's thermal properties was low and may be considered negligible. After five reprocessing cycles, the results showed an ∼8°C decrease of Tg in DSC, an increase of MFI, a decrease in viscosity and a slight decrease of HDT, which could be attributed to chain scission caused by consecutive cycles of exposure to shear stresses and high temperature. The material became slightly more rigid and fragile, as indicated by the mechanical tests.

We report the molecular structure and a single crystal EPR study at 9.8 and 33.9 GHz of a new copper(II) compound with the amino acid L-Glutamine, Cu[NH 2 CO 2 CH(CH 2 ) 2 -CONH 2 ] 2 . The Cu II ion is in an elongated octahedral environment equatorially trans-coordinated by two glutamine molecules acting as bidentate ligands through the nitrogen atom and one oxygen atom of each amino acid group, and axially by two carboxylate oxygen atoms of two neighboring glutamine molecules. Copper ions are arranged in layers connected by syn-anti carboxylate bridges that provide equatorial and apical ligands to the copper ions. Neighboring layers are connected by long chemical paths, which include two amino acid side chains connected by H bonds. Single crystal EPR spectra show a single exchange-collapsed resonance at both microwave frequencies for any magnetic field orientation. The evaluation of the molecular g-tensor from the angu-

A new series of dinuclear dysprosium­(III) complexes, [Dy2(LCH3 )2(NO3)2(MeOH)2] (I), [Dy2(LCH3 )2(NO3)2(DMF)2]·2DMF (II), [Dy2(LCl)2(NO3)2(DMF)2]·2DMF (III), and [Dy2(LCH3O)2(NO3)2(DMF)2] (IV), with 2,2′-[[(2-pyridinylmethyl)­imino]­di­(methylene)]­bis­(4-R-phenol), where R = CH3, Cl, and CH3O, were investigated as potential white light emitters. All octacoordinated dysprosium­(III) are phenoxo-bridged species and have a similar coordination environment. Nevertheless, I has a MeOH ligand molecule, while for II–IV a DMF ligand replaces that of MeOH. The nature of the coordinated solvent molecule plays an important role in the behavior of the thermal dependence of the Y/B (yellow/blue) emission ratio of the DyIII complexes (Y: 4F9/2 → 6H13/2, yellow and B: 4F9/2 → 6H15/2, blue transitions),, since for I the variation of this ratio is significant, while for the other DyIII complexes with DMF as ligand the ratio remains constant within experimental error. At room temperature the CIE (Commission International d’Eclairage) color coordinates for the DyIII complexes, I (0.286, 0.317), III (0.302, 0.324), and IV (0.322, 0.348) are close to the NTSC (National Television System(s) Committee) standard value for white color. Varying the temperature from 16 to 300 K the CIE coordinates for I change from the blueish to white region of the chromaticity diagram, while those of II present an inverse thermal dependence as compared to I. The CCT (Correlated Color Temperature) values at room temperature for I (8384 K), II (17235 K), and IV (5948 K) permit us to consider these complexes as candidates for white cold light emitters, the high value of II being uncommon. For I and II the CCT values vary strongly with temperature, showing a decrease with increasing temperature for I, and an increase with increasing temperature for II, thus making evident the influence on the photophysical properties of the nature of the coordinated solvent molecule in these complexes.

A series of luminescent phenoxo-bridged dinuclear TbIII complexes with tripodal ligands, 2,2′-[[(2-pyridinylmethyl)­imino]­di­(methylene)]-bis­(4-R-phenol), where R = CH3 (LCH3) (I), Cl (LCl) (II), CH3O (LCH3O) (III), COOCH3 (LCOOCH3) (IV), were prepared to probe the effect of para-substitution on the phenol ring of the ligand on the TbIII luminescence. For these TbIII complexes a complete suppression of the ligand-centered fluorescence is observed, which demonstrates an efficient ligand-to-metal energy transfer. Complex IV was found to be the one that shows the greater intensity of the emission at room temperature. The obtained quantum yields follow the trend IV > II ≫ I > III. The quantum yield for II and IV is approximately five times greater than those obtained for I and III, indicating that the LCl and LCOOCH3 are better sensitizers of the TbIII ions. These results were rationalized in terms of the variation of the energy gap between the triplet level (T1) of the ligand and the emissive 5D4 level of TbIII, due to the electron-acceptor or electron-donor properties of the substituents. The τav values are in the millisecond range for all the studied complexes and resulted independent of temperature. The Commission International d’Eclairage coordinates (CIE) for all complexes are in the green color region, being insensitive to the variation of temperature. Moreover, the color purity (CP) is ca. 90% for all complexes, being ca. 100% for IV. Thus, the introduction of electron-acceptor substituents on the ligand permitted us to improve the luminescent properties of the TbIII complexes.

An unusual and unique conformation of a paddle wheel type binuclear copper(II) complex containing acetate and acetamido ligands, {Cu2(μ2-O2CCH3)4}(OCNH2CH3) (1), was obtained by solvothermal synthesis. The structural characterization of this compound shows that the apical (acetamido) ligands are disposed at a 62° dihedral angle, generating a special conformation as a consequence of the synthetic method used. This conformation has not been reported in other paddle wheel copper(II) tetraacetate compounds. Electron paramagnetic resonance (EPR) spectra of powder samples of (1) were obtained at 9.5 and 33.8 GHz, while single crystal spectra were obtained at 33.8 GHz with a B0 applied in three orthogonal planes. The fit of the single crystal experimental data allowed gave g∥ = 2.345 ± 0.003, and g⊥ = 2.057 ± 0.005. The angular variation of the EPR line allows evaluation of the fine structure of (1), giving D = -0.337 ± 0.002 cm(-1) and E = -0.005 ± 0.001 cm(-1). The line width angular dependence, used together with the Anderson model and Kubo-Tomita theory, permitted the interdimer interaction to be evaluated as |J'| = (0.051 ± 0.002) cm(-1). Using the powder spectral temperature dependence it was possible to evaluate the intradinuclear exchange coupling constan J0 as -101 ± 2 cm(-1), which is considerably lower than that reported for other analogous copper(II) tetraacetate paddle wheel compounds (Cu(II)-PW), showing the remarkable effect of the conformation of the terminal ligands on the magnetic interaction.

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