Physicochemical and Sensory Properties of Arabica Coffee Beans of Arara cv. Dried Using Different Methods.

The coffee fruit is preferably harvested at the cherry stage, with high moisture and metabolic activity, and must then undergo a drying process for better preservation of the bean and its sensory attributes. In this context, this study aimed to characterize the final quality of the Arara cultivar Arabica coffee processed using the wet method and subjected to six drying methods: three conducted at the agro-industrial establishment (fixed-bed dryer, rotary drum dryer, and combined drying) and three laboratory-scale methods (convective oven, cast-tape drying, and suspended terrace). Drying was carried out to reduce the coffee's moisture content from an initial value of 46.2% on a wet basis (w.b.) to a final average value of 11.35% (w.b.). The fruits of in natura demucilaged coffee and the processed dry coffee beans were characterized for moisture, ash content, nitrogen compounds, lipids, total titratable acidity, organic acids, sugars, and the instrumental color of the beans. The sensory profile of the Arabica coffee was evaluated by five coffee specialists using the methodology proposed by the Specialty Coffee Association (SCA), and all the coffees were classified as a specialty.

Evaluation of antiplasmodial activity and cytotoxicity assays of amino acids functionalized magnetite nanoparticles: Hyperthermia and flow cytometry applications.

We report the synthesis of magnetite nanoparticles (MNP) and their functionalization with glycine (MNPGly), ß-alanine (MNPAla), L-phenylalanine (MNPPhAla), D-(-)-α-phenylglycine (MNPPhGly) amino acids. The functionalized nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), electron paramagnetic resonance (EPR), vibrating sample magnetometry (VSM), Mössbauer spectroscopy (MS), magnetic hyperthermia (MH), dynamic light scattering and zeta potential. The functionalized nanoparticles had isoelectric points (IEP) at pH ≃ 4.4, 5.8, 5.9 and 6.8 for samples MNPGly, MNPAla, MNPPhGly and MNPPhAla, respectively, while pure magnetite had an IEP at pH 5.6. In the MH experiments, the samples showed specific absorption rate (SAR) of 64, 71, 74, 81 and 66 W/g for MNP, MNPGly, MNPAla, MNPPhGly, and MNPPhAla, respectively. We used a flow cytometric technique to determine the cellular magnetic nanoparticles plus amino acids content. Magnetic fractionation and characterization of Resovist® magnetic nanoparticles were performed for applications in magnetic particle imaging (MPI). We have also studied the antiproliferative and antiparasitic effects of functionalized MNPs. Overall, the data showed that the functionalized nanoparticles have great potential for using as environmental, antitumor, antiparasitic agents and clinical applications.

Structure and magnetism of a binuclear Cu(II) pyrophosphate: transition to a 3D magnetic behaviour studied by single crystal EPR.

A binuclear Cu(II) compound [Cu2(bpa)2(P2O7)(H2O)2]·2.5H2O, 1, (bpa = 2,2'-bipyridylamine), with pairs of Cu(II) ions bridged by one pyrophosphate tetra-anion, was synthesized and crystallized. Its triclinic structure was determined by single-crystal X-ray diffraction. Electron paramagnetic resonance (EPR) spectra of single crystal samples of 1 were recorded for a fixed orientation of the magnetic field (B0) as a function of temperature (T) between 4.7 and 293 K, and at T = 4.7, 50 and 293 K, as a function of the orientation of B0. Below ∼8 K, the spectra are assigned to two types of mononuclear crystal defects hyperfine-coupled to one copper and two nitrogen nuclei. The g-matrices and hyperfine couplings at these T provide information about the structures of these defects. Above 10 K, the spectrum is dominated by the response of the bulk binuclear Cu(II) material, showing hyperfine interactions with two copper nuclei, collapsing to a single peak above 18 K when the units are magnetically connected, and the magnetic behaviour becomes 3D. We attribute the results above 10 K to the interplay of an AFM intrabinuclear exchange interaction J0 = -28(3) cm(-1) (defined as Hex = -J0S1·S2), and three orders of magnitude weaker exchange coupling with average magnitude |J1| ≥ 0.022 cm(-1) between Cu(II) ions in neighbouring binuclear units. The interplays between structure, exchange couplings, magnetic dimension and spin dynamics in the binuclear compound are discussed. A previously unreported situation, where the structure of the spectra arising from the anisotropic spin-spin interaction term (D) within the binuclear unit is averaged out, but the forbidden half field transition is not, is observed and explained.

Unusual conformation of a dinuclear paddle wheel copper(II) complex. Synthesis, structural characterization and EPR studies.

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.

Single crystal electron paramagnetic resonance spectra of Cu(II) ions in Cu(tyrosine)(2): a study of weak exchange interactions mediated by resonance assisted hydrogen bonds (RAHB).

EPR measurements have been performed on single crystals of [Cu(L-tyrosine)(2)](∞) at 33.8 GHz and at room temperature. The EPR spectra display partially resolved EPR lines for most orientations of the magnetic field in the ab plane, and only one resonance for orientations close to the crystal axes, while only a single line is observed along any direction in the ca and cb crystal planes. This behavior is a result of the selective collapse of the resonances corresponding to the four copper sites in the unit cell produced by the exchange interactions between the copper ions. The magnitudes of the exchange interactions between the copper ions were evaluated from the angular variation of the line width and the collapse of the EPR lines. The value |J(AD)/k(B)|=0.8 K between neighboring copper atoms at 4.942 Å is assigned to a syn-anti equatorial-apical carboxylate bridge with a total bond length of 6.822 Å, while the small value |J(AB)/k(B)|=0.004 K is assigned to a long bridge of 11 atoms with a total bond length of 19.186 Å, that includes one resonance assisted hydrogen bond (RAHB). This finding is discussed in terms of values obtained for similar paths in other model compounds and in proteins.

Exchange interactions through π-π stacking in the lamellar compound [{Cu(bipy)(en)}{Cu(bipy)(H2O)}{VO3}4]n.

Structural, magnetic, and powder and single-crystal electron paramagnetic resonance (EPR) studies were performed on [{Cu(bipy)(en)}{Cu(bipy)(H(2)O)}{VO(3)}(4)](n) (bipy = 2,2'-bipyridine, en = ethylenediamine), which is a new copper-vanadium hybrid organic-inorganic compound containing Cu(II) and V(V) centers. The oxovanadium units provide an anionic scaffolding to the structure, where two types of Cu(II) coordination modes, octahedral (Cu1) and square pyramidal (Cu2), contribute to the magnetic properties. The crystal structure contains layers including Cu1 and Cu2 ions, separated by stacked arrangements of 2,2'-bipyridine molecules. Each type of Cu(II) ion in these layers forms parallel spin chains described by exchange coupling parameters J(1) and J(2) for Cu1 and Cu2, respectively (exchange couplings defined as H(ex)(i,j) = -J(ij)S(i)S(j)), which, for necessity, are assumed to be equal to J. These chains are coupled by much weaker Cu1-Cu2 exchange interactions J(3) connecting neighbor Cu1 and Cu2 ions within a layer, through paths acting as rungs of a ladder chain structure. The average coupling J, which is antiferromagnetic (J < 0), according to the susceptibility data, is estimated with similar results with a mean field approximation (J = -1.4 cm(-1)), and with a uniform chain model (J = -1.7 cm(-1)). The EPR spectra of powdered samples and oriented single crystals are shown to be independent of J(1) and J(2), but are dependent on the weak coupling J(3), and the data allow a lower limit to be established: |J(3)| > 0.04 cm(-1). The spectra are also strongly sensitive to extremely weak coupling interactions with average magnitude J(4) between copper atoms in neighboring layers, separated by ∼10 Å, using the stacked 2,2'-bipyridine molecules, which produce a 2D-to-3D quantum phase transition. This is observed in single-crystal samples when the energy levels are changed with the orientation of the magnetic field. From the characteristics of these transitions, we estimate a value of |J(4)| = 0.0034 ± 0.0004 cm(-1) between Cu(II) ions in neighboring layers. This work emphasizes the important possibilities of EPR to evaluate extremely small exchange couplings between metal ions in a solid material, even in the presence of other much larger couplings.

Pyrophosphate-bridged Cu(II) chain magnet: {[Na3Cu(P2O7)(NO3)].3H2O}n.

A Cu(II)...Cu(II) pyrophosphate-bridged compound of formula {[Na(3)Cu(P(2)O(7))(NO(3))].3H(2)O}(n) (1) has been characterized. X-ray diffraction measurements show that it crystallizes in the monoclinic space group P2(1)/m, with unit cell dimensions a = 7.2492(5) A, b = 8.2446(6) A, c = 9.9050(7) A, beta = 107.123(1) degrees, and Z = 2. The structure consists of chains of Cu(II) cations at inversion symmetry sites bound to four equatorial oxygen atoms provided by two pyrophosphate anions halved by a symmetry plane and two axial oxygen atoms of nitrate anions. The molar magnetic susceptibility chi(0) of a powdered sample was measured in the temperature range 2 K < T < 273 K, and an isothermal magnetization curve, M(B(0),T), was obtained at T = 30 K, with the magnetic field B(0) between 0 and 5 T. Fitting a spin-chain model to the susceptibility data, we evaluate an antiferromagnetic exchange coupling 2J = -24.3(1) cm(-1) (defined as H(ex) = -2JS(i)S(j)) between Cu(II) neighbors. For any orientation of B(0), single-crystal electron paramagnetic resonance (EPR) spectra obtained at 9.8 and 33.9 GHz at 300 K display a single signal having a g matrix with orthorhombic symmetry, arising from the merger produced by the exchange interaction of the resonances corresponding to the two rotated Cu(II) sites. The g matrices of the individual molecules calculated assuming axial symmetry yielded principal values g(parallel) = 2.367(1) and g(perpendicular) = 2.074(1) at both frequencies, indicating a d(x(2)-y(2)) ground-state orbital for the Cu(II) ions. The angular variation of the EPR line width suggests exchange narrowing in a system with one-dimensional spin dynamics, as expected from the structure and susceptibility data. The results, discussed in terms of the crystal and electronic structures and of the spin dynamics of the compound, are compared with those obtained in other materials.

Magnetism and structure in chains of copper dinuclear paddlewheel units.

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

Alternate Cu2 and Er2 spin carriers in a carboxylate-bridged chain: EPR study.

We report powder EPR measurements at 9.48 GHz and temperatures of 4 K < or = T < or = 300 K and at 33.86 GHz and T = 300 K for the polymeric compound {[Cu2Er2(L)10(H2O)4].3H2O}n (HL = trans-2-butenoic acid) having alternate Cu2 and Er2 dinuclear units bridged by carboxylates along a chain. Above 70 K, when the Er(III) resonance is unobservable and uncoupled from the Cu(II) ions, the spectrum arises from the excited triplet state of antiferromagnetic Cu2 units, decreasing in intensity as T decreases, and disappearing when these units condensate into the singlet ground state. Fit of a model to the spectra at 9.48 and 33.86 GHz and 300 K gives g(Cu)(parallel) = 2.379, g(Cu)(perpendicular) = 2.065, D(Cu) = -0.340 cm(-1), and E(Cu) approximately 0 for the g-factors and zero field splitting parameters. From the T dependence of the intensity of the spectrum above 70 K, we obtain J(Cu-Cu) = -336(11) cm(-1) for the intradinuclear exchange interaction. Below 50 K, a spectrum attributed to Er(2) units appears, narrows, and resolves as T decreases, due to the increase of the spin-lattice relaxation time T1. The spectrum at 4 K allows calculating g values g1 = 1.489, g2 = 2.163, and g3 = 5.587 and zero field splitting parameters D(Er) = -0.237 cm(-1) and E(Er) = 0.020 cm(-1). The results are discussed in terms of the properties of the Cu and Er ions, and the crystal structure of the compound.