52 research outputs found
Functionalised tetrathiafulvalene- (TTF-) macrocycles: recent trends in applied supramolecular chemistry
Tetrathiafulvalene (TTF) has been extensively explored as a Ï-electron donor in supramolecular systems. Over the last two decades substantial advances have been made in terms of constructing elaborate architectures based on TTF and in exploiting the resulting systems in the context of supramolecular hostâguest recognition. The inherent electron-donating character of TTF derivatives has led to their use in the construction of highly efficient optoelectronic materials, optical sensors, and electron-transfer ensembles. TTFs are also promising candidates for the development of the so-called âfunctional materialsâ that might see use in a range of modern technological applications. Novel synthetic strategies, coupled with the versatility inherent within the TTF moiety, are now allowing the architecture of TTF-based systems to be tuned precisely and modified for use in specific purposes. In this critical review, we provide a âstate-of-the-artâ overview of research involving TTF-based macrocyclic systems with a focus on their use in supramolecular hostâguest recognition, as components in non-covalent electron transfer systems, and in the construction of âmolecular machinesâ
Tetrathiafulvalene Porphyrins
Four tetrathiafulvalene (TTF)-annulated porphyrins 1â4 were synthesized and characterized. All contain a tetraphenylporphyrin (TPP) core onto which four, two, or one TTF subunits were annulated. Absorption and fluorescence spectroscopic studies together with electrochemical investigations reveal that interactions between the porphyrin system and the annulated TTF units take place in solution. The annulation of one or more TTF units to the porphyrin core has a profound effect on the reduction potentials associated with this latter framework, with positive shifts in the range of 0.105 to 0.355 V and 0.200 to 0.370 V for the first and second reduction potential, respectively, compared to the corresponding processes in the model compound TPP, 18. The redox potentials for the first oxidation of the TTF units are considerably shifted in 4 (ÎEox1=+0.285 V) and 2 (ÎEox1=â0.140 V), whereas for 1 and 3 these potentials remain within the region expected for a normal TTF unit. Considerable changes in the second oxidation potential associated with the TTF subunits were seen for 2 (ÎEox1=â0.085) and 3 (ÎEox1=â0.175). The emission spectra of 1â4 revealed that the porphyrin fluorescence is almost quenched in the neutral state of the TTF-annulated porphyrins, a finding that is consistent with substantial electron transfer taking place from the TTF subunits to the porphyrin core. Oxidation of the TTF unit(s) (TTFâTTF.+) present in 1â4 leads to the emission intensity being restored
Tetrathiafulvalene-Calix[4]Pyrrole in the Chloride Anion Controled Molecular Recognition of 2,5,7-trinitro-9-dicyanomethylenefluorene-C60
Date du colloque : 05/2008International audienc
The Nuclear Physics of Hyperfine Structure in Hydrogenic Atoms
The theory of QED corrections to hyperfine structure in light hydrogenic
atoms and ions has recently advanced to the point that the uncertainty of these
corrections is much smaller than 1 part per million (ppm), while the
experiments are even more accurate. The difference of the experimental results
and the corresponding QED theory is due to nuclear effects, which are primarily
the result of the finite nuclear charge and magnetization distributions. This
difference varies from tens to hundreds of ppm. We have calculated the dominant
nuclear component of the 1s hyperfine interval for deuterium, tritium and
singly ionized helium, using a unified approach with modern second-generation
potentials. The calculated nuclear corrections are within 3% of the
experimental values for deuterium and tritium, but are roughly 20% discrepant
for helium. The nuclear corrections for the trinucleon systems can be
qualitatively understood by invoking SU(4) symmetry.Comment: 12 pages, 1 figure, latex - submitted to Physics Letters
Self-Assembled Monolayers of Mono-Tetrathiafulvalene Calix[4]pyrroles and Their Electrochemical Sensing of Chloride
Chloride anion sensing: Immobilization of a calix[4]pyrrole endowed with a redox-active mono-tetrathiafulvalene unit on a gold surface produces a redox-responsive self-assembled monolayer that allows for the electrochemical detection of chloride anions down to the submicromolar level (see figure)
Chloride Anion Controlled Molecular âSwitchingâ. Binding of 2,5,7-Trinitro-9-dicyanomethylenefluorene-C60 by Tetrathiafulvalene Calix[4]pyrrole and Photophysical Generation of Two Different Charge-Separated States
The binding of the snake-like trinitrodicyanomethylenefluorene-C60 derivative (TNDCF-C60) to the dynamic receptor, tetrathiafulvalene calix[4]pyrrole (TTF-calix[4]pyrrole), may be controlled via the use of a chloride anion as an external trigger. Whereas, in the absence of a chloride anion, the TNDCF ?tail? of the trinitrodicyanomethylenefluorene-C60 substrate binds to the TTF?calix[4]pyrrole in a 2:1 (substrate/receptor) stoichiometry in CH2Cl2 solution, addition of a chloride anion (yellow) leads the TNDCF tail to be displaced in favor of a bound C60 ?head?, a process that leads to the formation of a complex with overall 1:2:2 substrate/receptor/chloride anion stoichiometry. These chemical switching events are reflected in easy-to-visualize color changes, as well as in the production of two different kinds of charge-separated states following selective femtosecond photoexcitation
Binding studies of tetrathiafulvalene-calix[4]pyrroles with electron-deficient guests
The neutral meso-octamethylporphyrinogen derivative, tetraTTF-calix[4]pyrrole 1 (TTF=tetrathiafulvalene), acts as a multi-faceted receptor in that it interacts with an assortment of different guests in different ways. The conformation of receptor 1 can be reversibly switched between the 1,3-alternate conformation (i.e., 1, Fig. 1) and the cone conformation (i.e., 1·Clâ, Fig. 2) by the repetitive addition of chloride and sodium ions. In this paper, the results of detailed and systematic complexation studies involving both 1 and its chloride-bound complex, 1·Clâ, with a variety of guests are described. Receptor 1 binds quasi-planar nitroaromatic guests in its 1,3-alternate conformation, while release of these guests takes place upon addition of chloride anions. On the other hand, spherical fullerene guests are strongly bound by 1·Clâ. Finally, it was found that a bidentate guest, consisting of a quasi-planar 2,5,7-trinitro-9-dicyanomethylenefluorene moiety tethered to a spherical C60 fullerene, could be recognized by receptor 1 in either its 1,3-alternate or its chloride-bound cone conformation, albeit through very different binding modes
Halogen bonding-based anion coordination in calixarene/inorganic halide/diiodoperfluorocarbon assemblies
Epidural levobupivacaine alone or combined with different morphine doses in bitches under continuous propofol infusion
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