Showing papers by "Jean Roncali published in 2004"

Crown‐Tetrathiafulvalenes Attached to a Pyrrole or an EDOT Unit: Synthesis, Electropolymerization and Recognition Properties

Abstract: A crown-tetrathiafulvalene electroactive receptor has been covalently linked to electropolymerizable pyrrole or 3,4-ethylenedioxythiophene monomers. The synthetic route to the monofonctionalized tetrathiafulvalene (TTF) ligand has been optimized. Two derivatives of pyrrole (N- and 3-substituted) were synthesized. The various substituted monomers have been electropolymerized to produce polypyrrole (PP) and poly(ethylenedioxothiophene) (PEDOT) films bearing the electroactive TTF moiety. The electroactivity of the polymer films is efficiently controlled by the well-defined two-step redox behavior of the TTF unit. In the case of PEDOT, an alternative post-polymerization derivatization strategy has been used, involving the grafting of the crown-TTF ligand on the previously grown PEDOT backbone. Though chemical derivatization is realized under heterogeneous conditions, in the bulk of the film, this strategy proved to be particularly efficient. These electrodes constitute the first examples of conducting polymer-based modified electrodes incorporating a TTF electrochemical probe, able to interact with a guest ion, such as Ba2+. The cation recognition properties of these various electrodes have been analyzed by cyclic voltammetry and their electroactivity in water as well as their regeneration capability have been investigated.

3,4-Phenylenedioxythiophene (PheDOT): a novel platform for the synthesis of planar substituted π–donor conjugated systems

Abstract: 3,4-Phenylenedioxythiophene (PheDOT), a benzenic analogue of 3,4-ethylenedioxythiophene (EDOT), has been synthesized using two different routes namely etherification of 2,5-dicarboethoxy-3,4-dihydroxythiophene with halo-aromatics and transetherification of 3,4-dimethoxythiophene with catechols. Quantum calculations and electrochemical measurements show that replacement of the ethylene bridge of EDOT by a phenyl group leads to an increase of the HOMO level and to a stabilization of the cation radical, making electropolymerization of PheDOT more difficult than that of EDOT. The synthesis of several PheDOT derivatives is described together with preliminary results on their electrochemical polymerization and on the properties of the resulting polymers and copolymers.

Effect of substitution of 3,4-ethylenedioxythiophene (EDOT) on the electronic properties of the derived electrogenerated low band gap conjugated polymers

Abstract: Introduction of a long alkoxy chain at an sp3 carbon of the ethylenedioxy bridge of EDOT induces a large increase of the band gap of the resulting polymer.

Electrogenerated poly(thiophenes) derivatized by bipyridine ligands and metal complexes

Abstract: The synthesis of a series of bithiophenic precursors of electrogenerated conjugated polymers functionalized by bipyridine ligands is described. The precursor structure involves two polymerizable groups attached at both ends of a bipyridine ligand and fixed at an internal β-position of thiophene via an alkylsulfanyl or alkoxy spacer. Electrochemical and optical data show that the low polymerization potential resulting from the association of 3,4-ethylenedioxythiophene (EDOT) and alkylsulfanyl or alkoxy thiophene combined with the multi-site polymerization approach allows a straightforward electrosynthesis of extensively conjugated and stable functionalized polymers. On the basis of these results, iron and ruthenium complexes of these precursors have been synthesized and electropolymerized. The analysis of the electrochemical behavior of the resulting polymers shows that they exhibit the typical electrochemical signature of both the conjugated polythiophene backbone and the immobilized metal complex.

Quantum chemical DFT and spectroscopic study of a push–pull chromophore for second-order nonlinear optics containing bithiophene as the electron relay

Abstract: We report on a density functional theory and spectroscopic study of a π-conjugated push–pull chromophore with second order nonlinearities, 5-[1,3-bis(dicyanomethylidene)indan-2-ylidenemethyl]-5′-[(E)-4-N,N-dimethylaminobenzylidene)methyl]-2,2′-bithiophene. The effects of the intramolecular charge transfer (ICT) from the donor to the acceptor groups on the molecular geometry and atomic charge distribution of this NLO-phore are derived from its DFT//B3LYP/6-31G* minimum-energy structure and Natural Population Analysis. The optical absorptions of this chromophore in the UV–Vis spectral region are analyzed with the help of TDDFT//B3LYP/6-31G* calculations of one-electron vertical excitations and of the DFT//B3LYP/6-31G* topologies of the relevant molecular orbitals. The main infrared and Raman features of the NLO-phore are also analyzed by performing DFT//B3LYP/3-21G* vibrational calculations. The great resemblance, in peak positions and relative intensities, between the infrared and Raman spectra of this compound reveals that it really behaves as an efficient push–pull system.