Kane Jacob

Functionalization of Non-activated CH Bonds of Alkanes: An Effective and Recyclable Catalytic System Based on Fluorinated Silver Catalysts and Solvents

The complexes F(n)-Tp(4Bo,3Rf)Ag(L) (F(n)-Tp(4Bo,3Rf)=a perfluorinated hydrotris(indazolyl) borate ligand; L=acetone or tetrahydrofuran) efficiently catalyze the functionalization of non-activated alkanes such as hexane, 2,3-dimethylbutane, or 2-methylpentane by insertion of CHCO(2)Et units (from N(2)CHCO(2)Et, ethyl diazoacetate, EDA) into their C-H bonds. The reactions are quantitative (EDA-based), with no byproducts derived from diazo coupling being formed. In the case of hexane, the functionalization of the methyl C-H bonds has been achieved with the highest regioselectivity known to date with this diazo compound. This catalytic system also operates under biphasic conditions by using fluorous solvents such as Fomblin or perfluorophenanthrene. Several cycles of catalyst recovery and reuse have been performed, with identical chemo- and regioselectivities.

Nanoparticles of organic conductors: synthesis and application as electrode material in organic field effect transistors

Stabilization of TTF·TCNQ nanoparticles is studied by varying the ionic liquid nature and solvent medium. The best dispersion is obtained in an acetonitrile/acetone mixture and the smaller size by using [BMIM][BF4], as a stabilizing ionic liquid. Applications of well-dispersed TTF·TCNQ nanoparticles (mean diameter of about 35 nm) as electrode material in organic field-effect transistors are also reported.

Highly fluorinated aryl-substituted tris(indazolyl)borate thallium complexes: diverse regiochemistry at the B-N bond.

The synthesis and characterization (mainly by (19)F NMR and X-ray diffraction) of highly fluorinated aryl-4,5,6,7-tetrafluoroindazoles and their corresponding thallium hydrotris(indazolyl)borate complexes are reported [aryl = phenyl, pentafluorophenyl, 3,5-dimethylphenyl, 3,5-bis(trifluoromethyl)phenyl]. Thanks to N-H···N hydrogen bonds, the indazoles crystallize as dimers that pack differently depending on the nature of the aryl group. The thallium hydrotris(indazolyl)borate complexes Tl[Fn-Tp(4Bo,3aryl)] resulting from the reaction of aryl-4,5,6,7-tetrafluoroindazoles [aryl = phenyl, 3,5-dimethylphenyl, 3,5-bis(trifluoromethyl)phenyl] with thallium borohydride adopt overall C(3v) symmetry with the indazolyl groups bound to boron via their N-1 nitrogen in a conventional manner. When the perfluorinated pentaphenyl-4,5,6,7-tetrafluoroindazole is reacted with thallium borohydride, a single regioisomer of C(s) symmetry having one indazolyl ring bound to boron via its N-2 nitrogen, TlHB(3-pentafluorophenyl-4,5,6,7-tetrafluoroindazol-1-yl)(2)(3-pentafluorophenyl-4,5,6,7-tetrafluoroindazol-2-yl) Tl[F27-Tp((4Bo,3C6F5)*)], is obtained for the first time. Surprisingly, the perfluorinated dihydrobis(indazolyl)borate complex Tl[F(18)-Bp(3Bo,3C6F5)], an intermediate on the way to the hydrotris(indazolyl)borate complex, has C(s) symmetry with two indazolyl rings bound to boron via N-2. The distortion of the coordination sphere around Tl and the arrangement of the complexes in the crystal are discussed.

Charge injection from organic charge-transfer salts to organic semiconductors

Highly conducting films of organic charge-transfer (CT) salts are fabricated by a solution process from the dispersions stabilized by poly(vinylpyrrolidone). This method provides a general way to obtain conducting films of nonvolatile organic cation- and anion-radical salts with inorganic counter ions. Carrier injection from organic CT salts to organic semiconductors is investigated by using these films as electrodes in organic field-effect transistors. Efficient hole injection is observed not only from organic cation-radical salts but also from anion-radical salts to pentacene and sexithiophene. Electron injection is dominant from both types of CT salts to C60, but hole injection and ambipolar characteristics are observed for cation-radical salts. The Fermi levels of the CT salts are discussed on the basis of these observations.

Catalytic Functionalization of Methane and Light Alkanes in Supercritical Carbon Dioxide

The development of catalytic methods for the effective functionalization of methane yet remains a challenge. The best system known to date is the so-called Catalytica Process based on the use of platinum catalysts to convert methane into methyl bisulfate with a TOF rate of 10(-3) s. In this contribution, we report a series of silver complexes containing perfluorinated tris(indazolyl)borate ligands that catalyze the functionalization of methane into ethyl propionate upon reaction with ethyl diazoacetate (EDA) by using supercritical carbon dioxide (scCO2) as the reaction medium. The employment of this reaction medium has also allowed the functionalization of ethane, propane, butane, and isobutane.

Silver-Catalyzed Functionalization of Esters by Carbene Transfer: The Role of Ylide Zwitterionic Intermediates

The reaction of esters with ethyl diazoacetate catalyzed by the complex [F27–Tp  4 Bo,3 CF 2CF 3 Ag(acetone)] generates α‐(acyloxy)acetates in moderate to high yields. This is a novel transformation in the context of carbene‐transfer reactions from diazo compounds that, according to experimental and theoretical data, is suggested to occur through zwitterionic intermediates.

Nanoparticles of molecule-based conductors

State of the art molecule-based conductors that have been isolated as nanoparticles are reviewed. Research efforts in this field is justified by their insolubility and low vapour pressure, making their integration into electronic devices difficult. Their availability as nanoparticles would allow researchers to study their properties at the nanoscale and as stable dispersions, offering new opportunities for processing. Molecular conductors and superconductors that have been isolated as nanoparticles are: TTF·TCNQ, TTF[Ni(dmit)2]2, TTFCl0.77 and TTFBr0.59, (BEDT-TTF)Cl0.66 and (BEDT-TTF)2Br, (TMTSF)2ClO4 and (TMTSF)2PF6. Nanoparticle formation and shape depend on the stabilizing agent used for controlling the growth: ionic liquids, long-chain ammonium salts or neutral liquid polymers. The conductivities of the nanoparticle powders are reported.

Perfluorinated 1H-indazoles and hydrotris(indazol-1-yl)borates. Supramolecular organization and a new synthetic procedure to form scorpionate ligands

This paper describes the syntheses and full characterization of perfluorinated 1H-indazoles 2–5 and hydrotris(indazolyl)borate thallium complexes 6–9 that contain linear perfluoroalkyl chains varying from two to six carbon atoms in the 3-position. In the solid state, the perfluorinated 1H-indazoles exhibit supramolecular structures that depend on the length of the perfluoroalkyl chain. A catemer of order 3 is observed for the CF2CF3 derivative 2 (chiral space group P32), catemers of order 2 are observed for the C3F7 and C4F9 derivatives 3 (chiral space group P212121, one type of helix in the unit cell) and 4 (space group P21/n, two types of helices in the unit cell), respectively, and stacks of dimers are observed for the indazole with the longer C6F13 chain 5 (space group P21/c). The perfluorinated hydrotris(indazolyl)borate thallium complexes 6–9 [TlFn–Tp4Bo,3Rf] have been obtained by a new reaction based on the reaction of HBBr2 (generated in situ from BBr3 and Et3SiH) with the indazolates of 2–5 followed by cation exchange. The X-ray crystal structure of [TlF33–Tp4Bo,3C3F7] 7 shows that, in addition to coordination to the three nitrogens, the thallium is buried in a nest of fluorines with seven short intramolecular Tl⋯F contacts with the pendant perfluoropropyl chains. The potential of these highly fluorinated molecules to act as ligands is highlighted.

Vibrational and Optical Studies of Organic Conductor Nanoparticles

To create free electrons in organic solids and thus generate an organic material exhibiting electrical conductivity, a simple way is to build an organic complex, in which there is a charge transfer from the atoms or molecules of an electron donor (D) to those of an electron acceptor (A). In 1973, the charge transfer salt TTF·TCNQ (donor: tetrathiafulvalene, TTF; acceptor: tetracyanoquinodimethane, TCNQ) was synthesized (figure 1) (Ferraris et al., 1973). In TTF·TCNQ single crystals, TTF and TCNQ form segregated columnar stacks along the b-axis of the crystal structure. The interplanar spacings in the TTF and TCNQ molecular stacks at room temperature are 3.47 A and 3.17 A, respectively (Kistenmacher et al., 1974). The TTF and TCNQ molecular planes tilt at an angle of 24.5 ° and 34.0 °, respectively with respect to the b-axis forming a herringbone arrangement. As single crystals, this compound behaves like a metal (the dc conductivity increases with decreasing temperature) down to 54 K, temperature at which it undergoes a metal-to-semiconductor transition. The maximum of conductivity in TTF·TCNQ is along the b-axis (about 600 1 cm1). Conductivity values range from 10−2 to 1 1 cm1 in a direction perpendicular to the direction of maximum conductivity. The amount of charge transfer from the TTF donor molecule to the TCNQ acceptor molecule has been investigated by various techniques. Using X-ray photoelectron spectroscopy, a value of 0.56  0.05 has been extracted from the shape of the S2p signal (Ikemoto et al., 1977). Values in the range 0.500.60 have been obtained by a numerical integration of X-ray diffraction amplitudes (Coppens, 1975). However, the most convenient technique is based on infrared spectroscopy. Using the linear correlation of the nitrile stretching mode for TCNQ as a function of the degree of charge transfer, a value of 0.59  0.01 has been obtained (Chappell et al., 1981). Although synthesized for many years, TTF·TCNQ currently attracts much interest because of its interesting physical properties. Moreover, it is the one-dimensional conductor which is the most intensively processed in forms others than single crystals. For instance, TTF·TCNQ was prepared as thin films on (100)-oriented alkali halide substrates (Fraxedas et al., 2002), as self-organized monolayers on Au(111) (Yan et al., 2009), or as nanowires on stainless steel conversion coatings (Savy et al., 2007). We report in this chapter the preparation and spectral studies of TTF·TCNQ prepared as nanoparticles.

Synthesis, characterization, and thermoelectric properties of superconducting (BEDT-TTF)2I3 nanoparticles

The synthesis of (BEDT-TTF)2I3 in the presence of two neutral amphiphilic molecules [N-octylfurfurylimine and 1-octanamine, N-(2-thienylmethylene)] leads to single and aggregated nanoparticles of 2 to 6 nm size. The samples contain highly crystalline nanoparticles of the βCO-(BEDT-TTF)2I3 phase, confirmed by XRD. Temperature dependent resistance and magnetic susceptibility studies evidence the superconducting transition characteristics of the βCO-(BEDT-TTF)2I3 phase. The I–V curve of a single nanoparticle aggregate, measured using AFM, exhibits an expected semiconductor-like behaviour. Thermoelectric studies led to a ZT of 1.47 × 10−3 at 300 K.