Redox-active proligands from the direct connection of 1,3-dithiol-2-one to tetrathiafulvalene (TTF): syntheses, characterizations and metal complexation

International audienceIn the search for novel tetrathiafulvalene-substituted dithiolene ligands, two tetrathiafulvalene (TTF) molecules directly connected to 1,3-dithiol-2-one fragments have been synthesized and characterized by single crystal X-ray diffraction, electrochemical and spectroscopic analyses. TTF1 was obtained, in moderate yield, by the cross-coupling of 4,5-bis(methylthio)-1,3-dithiole-2-one with 4,4′-bis(1,3-dithiole-2-one) in triethylphosphite, whereas for TTF2, the 1,3-dithiol-2-one fragment was introduced, in high yield, by an original reaction of the alkyne group of an ethynyl TTF (Me3TTF-C[triple bond, length as m-dash]CH) with xanthogen in the presence of a radical initiator. Opening of the 1,3-dithiol-2-one fragments with sodium methanolate leads to the formation of two new 1,2-dithiolate ligands functionalized with redox-active TTF moieties, which can efficiently coordinate metals. As an illustration, two original heteroleptic bis(cyclopentadienyl)dithiolene titanium complexes were isolated and characterized

New Trends in Beverage Packaging Systems: A Review

New trends in beverage packaging are focusing on the structure modification of packaging materials and the development of new active and/or intelligent systems, which can interact with the product or its environment, improving the conservation of beverages, such as wine, juice or beer, customer acceptability, and food security. In this paper, the main nutritional and organoleptic degradation processes of beverages, such as oxidative degradation or changes in the aromatic profiles, which influence their color and volatile composition are summarized. Finally, the description of the current situation of beverage packaging materials and new possible, emerging strategies to overcome some of the pending issues are discussed

Functionalization of hydrogen-terminated silicon surfaces by tetrathiafulvalene and dithiolene complexes

La fonctionnalisation de surfaces de silicium hydrogéné par des films de molécules organiques suscite un intérêt croissant en raison des nombreuses applications potentielles (photovoltaïsme, détection chimique et biochimique, électronique moléculaire...). Dans ce cadre, nous avons cherché à greffer des tétrathiafulvalènes ou des complexes dithiolène de platine à ligand bipyridine, électroactifs, sur cette surface par hydrosilylation d’alcynes. Nous avons montré que ces composés organiques étaient bien immobilisés par une liaison robuste Si-C et nous avons noté la présence de plusieurs états redox stables et réversibles associés aux molécules greffées. Les méthodes de greffage direct et de post-fonctionnalisation de monocouches, ont permis l’obtention de films denses stables aux constantes de transfert de charge élevées.The functionalization of silicon surfaces by thin layers of organic molecules raises increasing interest due to the large extent of potential applications (photovoltaics, chemical and biochemical detection, molecular electronics and so on). In this context, we have prepared TTF and platinum dithiolene complex-modified silicon surfaces through a hydrosilylation reaction between hydrogen-terminated silicon and alkyne-terminated precursors. We have shown that these organic compounds were covalently bound to the surface through a robust Si-C bond. We have demonstrated that the electroactivity of the grafted molecules characterized by several reversible one-electron systems was maintained after the immobilization step. Post-functionalization and direct grafting reactions lead to dense and stable films, with high values of electron-transfer rate constants

Fonctionnalisation de surfaces de silicium hydrogéné par des tétrathiafulvalènes et des complexes dithiolène

La fonctionnalisation de surfaces de silicium hydrogéné par des films de molécules organiques suscite un intérêt croissant en raison des nombreuses applications potentielles (photovoltaïsme, détection chimique et biochimique, électronique moléculaire...). Dans ce cadre, nous avons cherché à greffer des tétrathiafulvalènes ou des complexes dithiolène de platine à ligand bipyridine, électroactifs, sur cette surface par hydrosilylation d alcynes. Nous avons montré que ces composés organiques étaient bien immobilisés par une liaison robuste Si-C et nous avons noté la présence de plusieurs états redox stables et réversibles associés aux molécules greffées. Les méthodes de greffage direct et de post-fonctionnalisation de monocouches, ont permis l obtention de films denses stables aux constantes de transfert de charge élevées.The functionalization of silicon surfaces by thin layers of organic molecules raises increasing interest due to the large extent of potential applications (photovoltaics, chemical and biochemical detection, molecular electronics and so on). In this context, we have prepared TTF and platinum dithiolene complex-modified silicon surfaces through a hydrosilylation reaction between hydrogen-terminated silicon and alkyne-terminated precursors. We have shown that these organic compounds were covalently bound to the surface through a robust Si-C bond. We have demonstrated that the electroactivity of the grafted molecules characterized by several reversible one-electron systems was maintained after the immobilization step. Post-functionalization and direct grafting reactions lead to dense and stable films, with high values of electron-transfer rate constants.RENNES1-Bibl. électronique (352382106) / SudocSudocFranceF

Multiredox tetrathiafulvalene-modified oxide-free hydrogen-terminated Si(100) surfaces.

International audienceTetrathiafulvalene (TTF) monolayers covalently bound to oxide-free hydrogen-terminated Si(100) surfaces have been prepared from the hydrosilylation reaction involving a TTF-terminated ethyne derivative. FTIR spectroscopy characterization using similarly modified porous Si(100) substrates revealed the presence of vibration bands assigned to the immobilized TTF rings and the Si-C═C- interfacial bonds. Cyclic voltammetry measurements showed the presence of two reversible one-electron systems ascribed to TTF/TTF(.+) and TTF(.+)/TTF(2+) redox couples at ca. 0.40 and 0.75 V vs SCE, respectively, which compare well with the values determined for the electroactive molecule in solution. The amount of immobilized TTF units could be varied in the range from 1.7 × 10(-10) to 5.2 × 10(-10) mol cm(-2) by diluting the TTF-terminated chains with inert n-decenyl chains. The highest coverage obtained for the single-component monolayer is consistent with a densely packed TTF monolayer

Multiredox Tetrathiafulvalene-Modified Oxide-Free Hydrogen-Terminated Si(100) Surfaces

Tetrathiafulvalene (TTF) monolayers covalently bound to oxide-free hydrogen-terminated Si(100) surfaces have been prepared from the hydrosilylation reaction involving a TTF-terminated ethyne derivative. FTIR spectroscopy characterization using similarly modified porous Si(100) substrates revealed the presence of vibration bands assigned to the immobilized TTF rings and the Si–CC– interfacial bonds. Cyclic voltammetry measurements showed the presence of two reversible one-electron systems ascribed to TTF/TTF^.+ and TTF^.+/TTF²⁺ redox couples at ca. 0.40 and 0.75 V vs SCE, respectively, which compare well with the values determined for the electroactive molecule in solution. The amount of immobilized TTF units could be varied in the range from 1.7 × 10^–10 to 5.2 × 10^–10 mol cm^–2 by diluting the TTF-terminated chains with inert <i>n</i>-decenyl chains. The highest coverage obtained for the single-component monolayer is consistent with a densely packed TTF monolayer

Controlled Grafting of Tetrathiafulvalene (TTF) Containing Diacetylenic Units on Hydrogen-Terminated Silicon Surfaces: From Redox-Active TTF Monolayer to Polymer Films

International audienceA tetrathiafulvalene (TTF)-terminated butadiyne derivative was synthesized and used for the preparation of redox-active TTF-modified hydrogen-terminated oxide-free silicon (Si−H) surfaces. TTF monolayer-modified silicon surfaces were produced when low grafting temperatures were used (typically 45 °C), whereas higher temperatures (90 °C) led to TTF polymer-modified surfaces. IR spectroscopy characterization provided evidence that TTF units bound to the surface through the formation of enyne linkers via hydrosilylation of the terminal alkyne bond. The TTF monolayers prepared at 45 °C were densely packed with a surface coverage of ca. 5.4 × 10−10 mol of TTF per cm2. For such systems, electrochemical measurements showed the redox signature of the bound TTF centers characterized by two reversible one-electron systems at ca. 0.40 and 0.73 V versus saturated calomel electrode (SCE). High values of electron-transfer rate constants were determined (>200 s−1) and ascribed to the presence of the conjugated bridge between the attached redox-active center and the underlying silicon surface. The TTF polymer-modified surfaces prepared at 90 °C resulted from the direct grafting of polymeric structures on Si−H and/or the postattachment functionalization of the preformed TTF monolayer. Polymerization process of the TTF-terminated butadiyne derivative was also investigated in solid state by means of differential scanning calorimetry and diffuse reflectance IR spectroscopy measurements

Charge-Gating Dibenzothiophene-S,S-dioxide Bridges in Electron Donor–Bridge–Acceptor Conjugates

The synthesis of a series of new electron donor–bridge–acceptor (D–B–A) conjugates (18–20) comprising electron-donating zinc(II) porphyrins (ZnPs) and electron-accepting fullerenes (C60s) connected through various co-oligomer bridges containing both dibenzothiophene-S,S-dioxide and fluorene units is reported. Detailed investigations using cyclic voltammetry, absorption, fluorescence, and femto/nanosecond transient absorption spectroscopy in combination with quantum chemical calculations have enabled us to develop a detailed mechanistic view of the charge-transfer processes that follow photoexcitation of ZnP, the bridge, or C60. Variations in the dynamics of charge separation, charge recombination, and charge-transfer gating are primarily consequences of the electronic properties of the co-oligomer bridges, including their electron affinity and the energy levels of the excited states. In particular, placing one dibenzothiophene-S,S-dioxide building block at the center of the molecular bridge flanked by two fluorene building blocks, as in 20, favors hole rather than electron transfer between the remote electron donors and acceptors, as demonstrated by exciting C60 rather than ZnP. In 18 and 19, in which one dibenzothiophene-S,S-dioxide and one fluorene building block constitute the molecular bridge, photoexcitation of either ZnP or C60 results in both hole and electron transfer. Dibenzothiophene-S,S-dioxide is thus shown to be an excellent building block for probing how subtle structural and electronic variations in the bridge affect unidirectional charge transport in D–B–A conjugates. The experimental results are supported by computational calculations

Assembly of Platinum Diimine Dithiolate Complexes onto Hydrogen-Terminated Silicon Surfaces

International audienceThe synthesis and structural characterization of the platinum diimine dithiolate complexes [Pt(R2bipy)(dmipi)] (dmipi = 4,5-dimercapto-l,3-dithiol-2-propargylimino and R = H, tBu) are described together with the X-ray crystal structure of the dithiolate proligand. These heteroleptic Pt complexes have been covalently bound to hydrogen-terminated silicon (100) surfaces using either a one-step or two-step procedure. The redox-active organometallic film modified surfaces were prepared from a hydrosilylation reaction at 90 °C of either the Pt complex bearing an ethyne terminal group or an ethyne-terminated dithiolate precursor followed by the subsequent anchoring of the Pt complex. Cyclic voltammetry measurements showed the presence of a single reversible one-electron-oxidation process corresponding to the oxidation of the complex into its radical cation species at 0.42 and 0.46 V vs SCE for the unsubstituted and tBu-substituted bipyridine dithiolate Pt complex-modified Si(100) surfaces, respectively. Such values compare well with those determined for the electroactive molecules in solution. Moreover, FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS) measurements were consistent with the expected structure of grafted molecular chains and revealed a significant oxidation of the underlying silicon surface. Nevertheless, the one-step procedure was found to lead to redox-active films of density higher than those produced from the two-step procedure. From XPS data, the surface coverage was estimated at 0.10 and in the range 0.03–0.06 Pt complex per surface silicon atom for the one-step and two-step procedures, respectively