A novel copper(II)-Schiff base complex containing pyrrole ring: Synthesis, characterization and its modified electrodes applied in oxidation of aliphatic alcohols

International audienceA new copper(II) complex Cu(II)-L containing N2O2 donor atoms has been prepared from 6-[3′-(N-pyrrol)propoxy]-2-hydroxyacetophenone and diaminoethane in the presence of copper acetate monohydrate. It was characterized by spectroscopic methods such as FT-IR, UV-vis, mass spectra, elemental analysis and cyclic voltammetry. The molecular structure of Cu(II)-L has also been confirmed by X-ray diffraction analysis. The electrochemical behavior of copper(II)-Schiff base complex containing pyrrol groups has been investigated in DMF and acetonitrile solutions using cyclic voltammetry. Thus, conducting polymeric films of polypyrrole were obtained on the surfaces of glassy carbon and ITO electrodes using copper(II) complex as monomer. The modified electrodes were electrochemically and morphologically characterized and their electrocatalytic properties in heterogeneous phase have also been investigated. The AFM studies show that the morphology of polypyrrole (PPy) films on ITO-electrodes depends on the number of cyclical scans. The electrocatalytic performances of this complex seem to be more efficient towards the electro-oxidation of isopropylic alcohol than any other kinds of alcohols such as methanol, ethanol and benzyl alcohol. The electro-reduction of carbon dioxide was also examined

3d and 4d coordination complexes and coordination polymers involving electroactive tetrathiafulvalene containing ligands

International audienceThe "through bond" approach has been recently developed to increase the interaction between the mobile π and localized d electrons in multifunctional molecular materials involving tetrathiafulvalene-based ligands. This article reviews the 3d and 4d coordination complexes and polymers elaborated from a library of tetrathiafulvalene derivatives containing ligands obtained recently in our group. The different synthetic ways of the complexes are highlighted as well as their chemical and physical properties

Wells-Dawson Polyoxometelates [HP2W18-nMonO62]Fe2.5, xH2O; n = 0, 6: Synthesis, spectroscopic characterization and catalytic application for dyes oxidation

International audienceThe synthesis, IR, 31P NMR and cyclic voltammetry characterizations of new Wells-Dawson-type heteropolyanions that contain iron, HFe2.5P2W18O62, 23H2O and HFe2.5P2W12Mo6O62, 22 H2O, are reported. The catalytic activity of these compounds was evaluated through the oxidation of methyl violet dye, by hydrogen peroxide. The influence of different parameters such as the initial pH, the initial H2O2 concentration, the catalyst mass, and the initial dye concentration have been studied

A new approach towards ferromagnetic conducting materials based on TTF-containing polynuclear complexes

International audienceFive complexes containing binuclear cation [Cu2(LH)2]2+ (LH2 = 1 : 2 Schiff base of 1,3-diaminobenzene and butanedione monoxime) were prepared and characterized. Metathesis of one perchlorate anion in [Cu2(LH)2(H2O)2](ClO4)2 (1) by anionic TTF-carboxylate (TTF-CO2−) leads to the complex [Cu2(LH)2(CH3OH)2](TTF-CO2)(ClO4)*H2O (2). Reactions of 1 with substituted pyridines bipy, dpe and TTF-CH = CH-py result in formation of the complexes {[Cu2(LH)2(bipy)](ClO4)2}n*2nH2O (3), [Cu2(LH)2(dpe)2](ClO4)2*2CH3OH (4) and [Cu2(LH)2(TTF-CH = CH-py)(H2O)](ClO4)2*1.5H2O (5), where bipy = 4,4′-bipyridine, dpe = trans-(4-pyridyl)-1,2-ethylene and TTF-CH = CH-py = 1-(2-tetrathiafulvalenyl)-2-(4-pyridyl)ethylene. Whereas complex 2 is built from discrete ionic particles (with rather long Cu-S contacts), compounds 1 and 3 contain 1D polymeric chains, in which structural units are bonded through Cu-O bonds or through bridging bipy molecule, respectively. Dinuclear complexes 4 and 5 are linked though π-stacking of dpe or TTF-CH = CH-py, respectively. All complexes are characterized by dominating ferromagnetic behavior with J values in the range from +9.92(8) cm−1 to +13.4(2) cm−1 for Hamiltonian H = -JS1S2. Magnetic properties of the compounds, containing stacks of aromatic molecules in crystal structures (4 and 5), correspond to ferromagnetic intradimer and antiferromagnetic intermolecular interactions (zJ′ = −0.158(3) and −0.290(2) cm−1, respectively). It was found that TTF-CH = CH-py ligand in [Cu2(LH)2(TTF-CH = CH-py)(H2O)]2+ could be electrochemically oxidized to cation-radical form in the solution

(Benzene­carbothio­amide-κS)­penta­carbonyl­tungsten(0)

The asymmetric unit of the title complex, [W(C7H7NS)(CO)5], comprises two independent mol­ecules. In each, the W atom is coordinated by five CO groups and the S atom of the benzencarbothioamide ligand in a distorted octa­hedral geometry. The crystal packing can be described as undulating layers of W(CO)5 and benzene­carbothio­amide parallel to (001). In the crystal, components are linked via inter­molecular N—H⋯O and C—H⋯O hydrogen bonds to form a dimeric chains along the [010] direction. Intra­molecular N—H⋯C inter­actions are also observed

Penta­carbon­yl(imidazolidine-2-thione-κS)tungsten(0)

In the title complex, [W(C3H6N2S)(CO)5], the W atom displays an octa­hedral coordination with five CO mol­ecules and an imidazolidine-2-thione mol­ecule. The W(CO)5 unit is coordinated by the cyclic thione ligand through a W—S dative bond. The W—S and C—S bond lengths are 2.599 (2) and 1.711 (9) Å, respectively. This last distance is significantly longer than that of free cyclic thio­ureas. The geometry of the title compound suggests sp 3-hybridization of the S atom caused by the greatly polarized linkage W—S—C bond angle, which is close to tetra­hedral [109.50 (3)°]. In the crystal packing, N—H⋯O and N—H⋯S hydrogen-bonding inter­actions stabilize the structure and build up chains parallel to [101]

Field-Induced Dysprosium Single-Molecule Magnet Based on a Redox-Active Fused 1,10-Phenanthroline-Tetrathiafulvalene-1,10-Phenanthroline Bridging Triad

Tetrathiafulvalene and 1,10-phenanthroline moieties present, respectively remarkable redox-active and complexation activities. In this work, we investigated the coordination reaction between the bis(1,10-phenanthro[5,6-b])tetrathiafulvalene triad (L) and the Dy(hfac)3·2H2O metallo precursor. The resulting {[Dy2(hfac)6(L)]·CH2Cl2·C6H14}3 (1) dinuclear complex showed a crystal structure in which the triad L bridged two terminal Dy(hfac)3 units and the supramolecular co-planar arrangement of the triads is driven by donor-acceptor interactions. The frequency dependence of the out-of-phase component of the magnetic susceptibility highlights three distinct maxima under a 2000 Oe static applied magnetic field, a sign that 1 displays a Single-Molecule Magnet (SMM) behavior with multiple magnetic relaxations. Ab initio calculations rationalized the Ising character of the magnetic anisotropy of the DyIII ions and showed that the main anisotropy axes are perpendicular to the co-planar arrangement of the triads. Single-crystal rotating magnetometry confirms the orientation of the main magnetic axis. Finally combining structural analysis and probability of magnetic relaxation pathways through Quantum Tunneling of the Magnetization (QTM) vs. excited states (Orbach), each DyIII center has been attributed to one of the three observed magnetic relaxation times. Such coordination compound can be considered as an ideal candidate to perform redox-magnetic switching

Synthesis, Crystal Structure, Magnetic, and Electron Paramagnetic Resonance Properties of a Spiroconjugated Biradical. Evidence for Spiroconjugation Exchange Pathway

A spiroconjugated nitronyl nitroxide biradical, 6,6‘-(4,4,5,5-tetramethylimidazolidine-3-oxide-1-oxyl)-3,3,3‘,3‘-tetramethyl-1,1‘-spirobisindane (1), has been prepared by functionalization of a 3,3,3‘,3‘-tetramethyl-1,1‘-spirobisindane framework followed by Ullman condensation and subsequent oxidation. The biradical crystallizes in the monoclinic space group C2/c with four molecules in the unit cell of dimensions a = 24.861(10) Å, b = 12.129(3) Å, and c = 12.258(6) Å. X-ray analysis of a blue-plate single crystal has revealed dihedral angles of 28° between the nitronyl nitroxide moiety and aromatic ring with intramolecular through space radical−radical distances of 8.25 and 10.11 Å. In the solid state, the temperature dependence of the molar magnetic susceptibility reveals antiferromagnetic interactions. These interactions are best fit using a pair model, affording the value J = −4.0 cm^(-1) where J is the interaction parameter appearing in the spin Hamiltonian H = −JS_1·S_2. The field dependence of the magnetization measured at 2 K is consistent with a pair model. Frozen matrix EPR spectra of biradical 1 in CH_2Cl_2 at 100 K shows a half field transition at 1700 G. Temperature dependence of the half field transition intensity has been found to be consistent with a ground singlet state and thermally accessible triplet state. The magnetic interaction observed in the solid state is also observed in solution. Thus, room-temperature solution spectra display a nine-line pattern, with hyperfine coupling to four “equivalent” nitrogen atoms and a hyperfine coupling constant a_N = 3.8 G. Temperature dependence of the solution EPR spectra of biradical 1 displays alternating line width effects caused by conformational dynamics in solution. This behavior has been attributed to modulation of exchange and hyperfine interactions most likely caused by rotational motion about the nitronyl nitroxide−phenyl bond. Biradical 1 therefore exists as a ground-state singlet with a thermally accessible triplet at ca. 4 cm^(-1) higher in energy with a conformational dependence of intramolecular exchange in solution. This coupling may present evidence for spiroconjugation as an exchange pathway. Density functional calculations (B3/6-311G(D)) have been performed to investigate this possibility