Interactions of thiophenes and acidophilic,thermophilic bacteria

The growth and oxygen consumption of a variety of thermophilic, acidophilic bacteria in the presence of thiophene-2-carboxylate (T2C) and dibenzothiophene (DBT) have been determined. T2C was extremely toxic to the acidophiles in comparison with neutrophiles, but appeared to be degraded by a heterotrophicSulfolobus- like thermophile. DBT proved to be unstable at high temperatures, even in the absence of bacteria, and was not a substrate for the thermophiles.     

Alkaline side-coordination strategy for the design of nickel(II) and nickel(III) bis(1,2-diselenolene) complex based materials

The deprotonated form of the pyrazine-2,3-diselenol (pds) ligand, pds(2-), reacts with Ni(II) inorganic salts to form the nickel compounds [Ni(II)(pds)(2)](nBu(4)N)(2) (1), [Ni(II)(pds)(2)]Na(2).2H(2)O (2), and [Ni(III)(pds)(2)](2)Na(2).4H(2)O (3), depending on the reaction conditions. They are characterized by NMR, EPR, UV-vis, and IR spectroscopies, elemental analysis, cyclic voltammetry, and X-ray crystallography. The crystal structure of compound 3 shows the formation of segregated stacks of Ni(pds)(2-) units, with a strong dimerization along the stacks. The stacked fashion of the crystal packing was expected since the supramolecular forces of the alkaline side coordination to the pyrazine moieties dominate, as happens in the recently reported analogous copper system [Cu(III)(pds)(2)]Na.2H(2)O. The structure of 2 further emphasizes the alkaline coordination as the dominating supramolecular event, and an orthogonal array of 2D layers is observed. The absence of alkaline cations in complex 1 is reflected in a crystal packing with isolated complex Ni(pds)(2)(2-) units. The dimerization found in the paramagnetic Ni(III) complex 3 promotes a very strong antiferromagnetic interaction, leading to a singlet ground state.     

Periodic Solutions of the Duffing DifferentialEquation Revisited via the Averaging Theory

We use three different results of the averaging theory of first order for studying the existence of new periodic solutions in the two Duffing differential equations $ddot y+ a sin y= b sin t$ and $ddot y+a y-c y^3=bsin t$, where $a$, $b$ and $c$ are real parameters.     

Limit Cycles of Piecewise Smooth Differential Equations on Two Dimensional Torus

In this paper we study the limit cycles of some classes of piecewise smooth vector fields defined in the two dimensional torus. The piecewise smooth vector fields that we consider are composed by linear, Ricatti with constant coefficients and perturbations of these one, which are given in (3). Considering these piecewise smooth vector fields we characterize the global dynamics, studying the upper bound of number of limit cycles, the existence of non-trivial recurrence and a continuum of periodic orbits. We also present a family of piecewise smooth vector fields that posses a finite number of fold points and, for this family we prove that for any 2k number of limit cycles there exists a piecewise smooth vector fields in this family that presents k number of limit cycles and prove that some classes of piecewise smooth vector fields presents a non-trivial recurrence or a continuum of periodic orbits.     

Cyclometallated platinum(II) compounds with imine ligands derived from amino acids: Synthesis and oxidative addition reactions

The reactions of [PtMe₂(μ-SMe₂)]₂ with imines 4-ClC₆H₄CHNCHRCO₂Me (R = H (1a), Me (1b), ⁱPr (1c), CH₂C₆H₄(4’-OH) (1d), C₆H₅ (1e), CH₂C₆H₅(1f)) derived from natural amino acids produced under mild conditions cyclometallated platinum(II) compounds [PtMe{κ²-(C,N)-4-ClC₆H₃CHNCHRCO₂Me}(SMe₂)] (2a-2f). These compounds gave the corresponding phosphine derivatives [PtMe{κ²-(C,N)-4-ClC₆H₃CHNCHRCO₂Me}(PPh₃)] (3a-3f). The corresponding cyclometallated platinum(IV) compounds [PtMe₂I{κ²-(C,N)-4-ClC₆H₃CHNCHRCO₂Me}(PPh₃)] (4) arising from intermolecular oxidative addition of methyl iodide were obtained with a high degree of stereo selectivity. Analogous results were obtained for imine 2,6-Cl₂C₆H₃CHNCH(CH₂C₆H₅)CO₂Me (1g) in a process involving intramolecular oxidative addition of a C-Cl bond. The obtained compounds were fully characterized including structure determinations for compounds 3f, 4d and 4f.     

Towards the detection of single polychlorotriphenylmethyl radical derivatives by means of Electron Spin Noise STM

The Electron Spin Noise Scanning Tunnelling Microscopy (ESN-STM) technique is one of the most promising techniques detecting one single spin, combining the spatial resolution of the STM with the ability of spectral resolution and spin manipulation of Electron Spin Resonance. After its first observation, the effectiveness of this technique has been tested by different groups to study the properties of small aggregates or single organic radical molecules.We report on the ongoing ESN-STM study on nano-aggregates of tris(2,4,6-thrichlorophenyl)methyl radical (TTM) derivatives, whose possibility to be used as wires, switches and memory devices has already been investigated in bulk. After deposition on Au(111), TTM radicals preserved their magnetism. To treat the collected noise data we followed a statistical approach; some peculiar characteristics of this analysis will be addressed.