N,N′‐Bis(2‐tosyl­amino­benzyl­idene)‐1,2‐ethanedi­amine

The structure of the title compound, C₃₀H₃₀N₄O₄S₂, is highly conditioned in the solid state by two strong N—H?N interactions. The values of the distances between the aminic N atoms [5.865 (3) Å] and the iminic N atoms [2.930 (4) Å], in conjunction with the long distance between the S atoms of the two tosyl groups [7.673 (1) Å], suggest that when the molecule acts as a ligand it will provide a single cavity for N₄ coordination to the metal centre.     

Analysis of an algorithm for the Galerkin-characteristic method

Summary It is shown that the interpretation of the Galerkin-Characteristic method for the scalar advection equation in the framework of particle methods yields a computationally efficient algorithm. Such an algorithm consists of updating the dependent variable at the grid points by cubic spline interpolation at the feet of the characteristic curves. The algorithm is unconditionally stable. The error analysis in the maximum norm shows that for sufficiently smooth functions the feet of the characteristic curves are points of high order convergence.     

Direct determination of molybdenum in mineral waters by atomic absorption spectrometry with electrothermal atomization

A new method for the direct determination of molybdenum by ETA-AAS in mineral waters without prior separation or concentration is proposed. With careful control of the graphite furnace conditions selective volatilization of the salt matrix is successfully attained. The possible spectroscopic interference due to common metals as well as the reproducibility, precision and repeatability of the method has been studied and the molybdenum content of 21 mineral waters measured.     

CZE separation of amitrol and triazine herbicides in environmental water samples with acid-assisted on-column preconcentration

A simple analytical scheme for the detection and quantification of amitrol and triazine herbicides (atrazine, ametryn and atraton) and degradation product (2‐hydroxyatrazine) in environmental water samples by CZE is reported. On‐column preconcentration of analytes from untreated water samples (mineral, spring, tap and river water) is accomplished by introducing an acid plug (200 mM citrate of pH 2.0) after the sample and then proceeding with the CZE separation, using 100 mM formiate buffer of pH 3.5 as running buffer and 25.0 KV as separation voltage. UV detection at 200 nm provides LODs from 50 to 300 nM in untreated samples and they were lowered tenfold by sample preconcentration by evaporation. Calculated recoveries were typically higher than 90%. Minimal detectable concentration of the electroactive amitrol could be decreased about 20‐fold when electrochemical detection was employed by monitoring the amperometric signal at +800 mV using a carbon paste electrode (LOD of 9.6 nM, 0.81 μg/L, versus 170 nM, 14.3 μg/L, using amperometric and UV detection, respectively) in untreated water samples.     

Interaction of Mn(acac)3 with Asymmetrical Schiff Base Ligands containing an Amido Group

Interaction of asymmetrical Schiff base ligands H₃Lⁿ [where H₃Lⁿ are substituted 3–aza–4–(2–hydroxyphenyl)–N– (2–hydroxyphenyl)but–3–enamide] with Mn(acac)₃ (acac = acetylacetonate) has been investigated. Two different type of manganese(III) complexes have been obtained depending on the nature of the substituents on the ligand. We have found that ligands containing donor substituents drives to the formation of two different kinds of complexes from the same reaction: Mn(Lⁿ)(H₂O)_x ( 1a–5a ) and [Mn(HLⁿ)(acac)](H₂O)_y ( 1b–5b ) (where Lⁿ and HLⁿ signify the ligand in its trianionic and dianionic form, respectively). However, when the substituents are electron withdrawing or poor donor only compounds of the type [Mn(HLⁿ)(acac)](H₂O)_y ( 6–10 ) are obtained. All these compounds have been characterized by elemental analyses, IR and ¹H NMR spectroscopy, FAB mass spectrometry, magnetic measurements and molar conductivities. The electrochemical behaviour of these complexes has also been studied.     

Dinuclear nickel complexes with a Ni(2)O(2) core: a structural and magnetic study

The acetylacetonate complexes [Ni(2)L(1)(acac)(MeOH)] x H(2)O, 1 x H(2)O and [Ni(2)L(3)(acac)(MeOH)] x 1.5H(2)O, 2 x 1.5H(2)O (H(3)L(1) = (2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine and H(3)L(3) = (2-(5-bromo-2-hydroxyphenyl)-1,3-bis[4-(5-bromo-2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine) were prepared and fully characterised. Their crystal structures show that they are dinuclear complexes, extended into chains by hydrogen bond interactions. These compounds were used as starting materials for the isolation of the corresponding [Ni(2)HL(x)(o-O(2)CC(6)H(4)CO(2))(H(2)O)] x n MeOH and [Ni(2)HL(x)(O(2)CCH(2)CO(2))(H(2)O)]x nH(2)O dicarboxylate complexes (x = 1, 3; n = 1-3). The crystal structures of [Ni(2)HL(1)(o-O(2)CC(6)H(4)CO(2))(H(2)O)] x MeOH, 3 x MeOH, [Ni(2)HL(3)(o-O(2)CC(6)H(4)CO(2))(H(2)O)] x 3 MeOH, 4 x 3 MeOH and [Ni(2)HL(1)(O(2)CCH(2)CO(2))(H(2)O)] x 2.5H(2)O x 0.25 MeOH x MeCN, 5 x 2.5H(2)O x 0.25 MeOH x MeCN, were solved. Complexes 3-5 show dinuclear [Ni(2)HL(x)(dicarboxylate)(H(2)O)] units, expanded through hydrogen bonds that involve carboxylate and water ligands, as well as solvate molecules. The variable temperature magnetic susceptibilities of all the complexes show an intramolecular ferromagnetic coupling between the Ni(II) ions, which is attempted to be rationalized by comparison with previous results and in the light of molecular orbital treatment. Magnetisation measurements are in accord with a S = 2 ground state in all cases.     

Evidence of the presence of opticlike collective modes in a liquid from neutron scattering experiments

Inelastic neutron scattering data from liquid DF close to the melting point show, in addition to spectra comprising quasielastic and heavily damped acoustic motions, an intense, nondispersive band centered at about 27 meV along with a broader higher energy feature. Observation of the former band provides the first direct verification of the existence within the liquid state of collective opticlike excitations as predicted by molecular dynamics simulations. The latter corresponds to mainly reorientational motions assigned from mode eigenvector analysis carried out by computer simulations.