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Kim M Baines - One of the best experts on this subject based on the ideXlab platform.
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a cryptand encapsulated germanium ii Dication
Science, 2008Co-Authors: Paul A Rupar, Viktor N Staroverov, Kim M BainesAbstract:Unlike cations of metals such as sodium or calcium, oxidized silicon and germanium centers generally require strongly bound covalent ligands. We report the synthesis and characterization of a germanium(II) Dication in the form of the salt (Ge·cryptand[2.2.2])(O3SCF3)2. The salt is isolated in 88% yield from the reaction of cryptand [2.2.2] and an N-heterocyclic carbene complex of GeCl(O3SCF3) as an air-sensitive, white solid. The crystal structure of the salt shows minimal interaction between the cryptand-encapsulated germanium(II) ion and the two –O3SCF3 counterions. These results suggest a widely expanded role of cryptands and related molecules in stabilizing nonmetallic cations.
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a germanium ii centered Dication
Journal of the American Chemical Society, 2007Co-Authors: Paul A Rupar, Viktor N Staroverov, Paul J Ragogna, Kim M BainesAbstract:The Dicationic 42+ complex with three N-heterocyclic carbenes coordinated to a germanium center is reported. The complex was characterized by 1H NMR and FT Raman spectroscopy, and the structure was determined by single-crystal X-ray diffraction. Electronic structure calculations reveal a partial positive charge at germanium and that the germanium lone pair shows no evidence for π bonding.
Jana Roithová - One of the best experts on this subject based on the ideXlab platform.
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probing isomers of the benzene Dication in a low temperature trap
Journal of the American Chemical Society, 2014Co-Authors: Juraj Jasik, Dieter Gerlich, Jana RoithováAbstract:The structure of doubly ionized benzene has been spectroscopically studied for the first time. Helium-tagged complexes were prepared at temperatures below 4 K and analyzed using infrared predissociation spectroscopy. Double ionization of benzene yields primarily high-energy Dications with a six-membered-ring structure. Some of the Dications undergo rearrangement to a more stable pyramidal isomer with a C5H5 base and CH at the apex. By means of isomer-selective heating by a CO2 laser, infrared predissociation spectra of both the classical and pyramidal Dications were obtained.
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Reactivity of C9Hn2+ Dications with methane
International Journal of Mass Spectrometry, 2012Co-Authors: Jana Vachelová, Jana RoithováAbstract:Abstract The reactivities of C 9 H x 2+ Dications ( x = 6–8) generated by electron ionization (EI) of indene, 1-phenylpropyne, and 3-phenylpropyne, respectively, were studied in thermal collisions with methane. The most reactive Dications correspond to dehydrogenated C 9 H 6 2+ , which show about 65% yield of C–C coupling products. The yield of coupling products in the reactions of radical Dications C 9 H 7 2+ drop to about 15% and the reactivity is dominated by electron transfer and charge-separation processes. The reaction between C 9 H 8 2+ and methane leads mostly to proton transfer. There are differences between reactivities of analogous Dications generated from different neutral precursors and therefore it can be stated that even Dications generated by EI retain a partial memory of the structure of the neutral precursor.
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Formation of Organoxenon Dications in the Reactions of Xenon with Dications Derived from Toluene
Chemistry: A European Journal, 2011Co-Authors: Zins El, Petr Milko, Detlef Schröder, Julia Aysina, Daniela Ascenzi, Jan Zabka, Christian Alcaraz, Stephen D. Price, Jana RoithováAbstract:The bimolecular reactivity of xenon with C(7)H(n)(2+) Dications (n=6-8), generated by double ionization of toluene using both electrons and synchrotron radiation, is studied by means of a triple-quadrupole mass spectrometer. Under these experimental conditions, the formation of the organoxenon Dications C(7)H(6)Xe(2+) and C(7)H(7)Xe(2+) is observed to occur by termolecular collisional stabilization. Detailed experimental and theoretical studies show that the formation of C(7)H(6)Xe(2+)+H(2) from doubly ionized toluene (C(7)H(8)(2+)) and xenon occurs as a slightly endothermic, direct substitution of dihydrogen by the rare gas with an expansion to a seven-membered ring structure as the crucial step. For the most stable isomer of C(7)H(6)Xe(2+), an adduct between the cycloheptatrienyldiene Dication and xenon, the computed binding energy of 1.36 eV reaches the strength of (weak) covalent bonds. Accordingly, electrophiles derived from carbenes might be particularly promising candidates in the search for new rare-gas compounds.
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selective dissociation in Dication molecule reactions
Physical Chemistry Chemical Physics, 2010Co-Authors: Michael A Parkes, Jana Roithová, Detlef Schröder, Stephen D. Price, Jessica F. Lockyear, Zdenek HermanAbstract:The single electron transfer reactions between 13CO22+ and 12CO2 and between 18O22+ and 16O2 have been studied, using a position-sensitive coincidence technique, to test recently proposed explanations for the preferential dissociation of the 13CO2+ ion (the capture monocation) formed following electron transfer to 13CO22+. In our studies of the carbon dioxide collision system, in agreement with previous work, the capture monocation shows a greater propensity to dissociate than the monocation formed from the neutral, 12CO2+ (the ejection monocation). The coincidence data clearly show that the dissociation pathways of the 13CO2+ and 12CO2+ ions are different and are consistent with the ejection monocation dissociating via population of the C2Σ+g state, whilst the capture ion is predominantly directly formed in dissociative quartet states. This state assignment is in accord with an expected preference for one-electron transitions in the electron transfer process. A propensity for one-electron transitions also rationalizes our observation that following dissociative single electron transfer between 18O22+ and 16O2 the ejection monocation (16O2+) preferentially dissociates; the opposite situation to that observed for carbon dioxide. The coincidence results for this reaction indicate the 16O2+ dissociation results from population of the B(2Σ−g) state. The less favoured dissociation of the capture monocation clearly involves population of a different electronic state(s) to those populated in the ejection ion. Indeed, the experimental data are consistent with the dissociation of the capture monocation via predissociated levels of the b(4Σ−g) state. Since the population of the B(2Σ−g) state from the neutral O2 molecule involves a one-electron transition, and the population of the valence dissociative states of O2+ from the Dication are multi-electron processes, the preferential dissociation of the ejection monocation in this collision system can be rationalized by the same principles used to explain the electron transfer reactivity of CO22+ with CO2.
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Generation of the ArCF22+ Dication
Journal of Physical Chemistry Letters, 2009Co-Authors: Jessica F. Lockyear, Jana Roithová, Stephen D. Price, Kevin M. Douglas, Malgorzata Karwowska, Karol J. Fijalkowski, Wojciech Grochala, Marek Remeš, Detlef SchröderAbstract:Thermal reactions of the CF32+ Dication with argon lead to the formation of an ArCF22+ Dication, a new type of metastable species with an argon−carbon bond. None of the other rare gases undergo a similar reaction with CF32+. For the lighter rare gases (He and Ne), no reactions with CF32+ other than those due to electronically excited reactant ions are observed, whereas for the heavier rare gases (Kr and Xe), the prevailing reactive pathways involve single-electron transfer. At elevated collision energies, single-electron transfer predominates for collisions with all rare gases (He−Xe).
Olivier Cuisenaire - One of the best experts on this subject based on the ideXlab platform.
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locally adaptable mathematical morphology using distance transformations
Pattern Recognition, 2006Co-Authors: Olivier CuisenaireAbstract:We investigate how common binary mathematical morphology operators can be adapted so that the size of the structuring element can vary across the image pixels. We show that when the structuring elements are balls of a metric, locally adaptable erosion and dilation can be efficiently implemented as a variant of distance transformation algorithms. Opening and closing are obtained by a local threshold of a distance transformation, followed by the adaptable dilation.
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Locally adaptable mathematical morphology
IEEE International Conference on Image Processing 2005, 2005Co-Authors: Olivier CuisenaireAbstract:We investigate how common binary mathematical morphology operators can be adapted so that the size of the structuring element (SE) can vary across the image. We show that when the SE are balls of a metric, locally adaptable erosion and dilation can be efficiently implemented as a variant of distance transformation algorithms. Opening and closing are obtained by a local threshold of a distance transformation, followed by the adaptable dilation.
Paul A Rupar - One of the best experts on this subject based on the ideXlab platform.
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a cryptand encapsulated germanium ii Dication
Science, 2008Co-Authors: Paul A Rupar, Viktor N Staroverov, Kim M BainesAbstract:Unlike cations of metals such as sodium or calcium, oxidized silicon and germanium centers generally require strongly bound covalent ligands. We report the synthesis and characterization of a germanium(II) Dication in the form of the salt (Ge·cryptand[2.2.2])(O3SCF3)2. The salt is isolated in 88% yield from the reaction of cryptand [2.2.2] and an N-heterocyclic carbene complex of GeCl(O3SCF3) as an air-sensitive, white solid. The crystal structure of the salt shows minimal interaction between the cryptand-encapsulated germanium(II) ion and the two –O3SCF3 counterions. These results suggest a widely expanded role of cryptands and related molecules in stabilizing nonmetallic cations.
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a germanium ii centered Dication
Journal of the American Chemical Society, 2007Co-Authors: Paul A Rupar, Viktor N Staroverov, Paul J Ragogna, Kim M BainesAbstract:The Dicationic 42+ complex with three N-heterocyclic carbenes coordinated to a germanium center is reported. The complex was characterized by 1H NMR and FT Raman spectroscopy, and the structure was determined by single-crystal X-ray diffraction. Electronic structure calculations reveal a partial positive charge at germanium and that the germanium lone pair shows no evidence for π bonding.
Andrzej Rajca - One of the best experts on this subject based on the ideXlab platform.
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high spin diradical Dication of chiral π conjugated double helical molecule
Journal of the American Chemical Society, 2019Co-Authors: Hui Zhang, Arnon Olankitwanit, Suchada Rajca, Andrzej RajcaAbstract:We report an air-stable diradical Dication of chiral D2-symmetric conjoined bis[5]diazahelicene with an unprecedented high-spin (triplet) ground state, singlet triplet energy gap, ΔEST = 0.3 kcal mol–1. The diradical Dication possesses closed-shell (Kekule) resonance forms with 16 π-electron perimeters. The diradical Dication is monomeric in dibutyl phthalate (DBP) matrix at low temperatures, and it has a half-life of more than 2 weeks at ambient conditions in the presence of excess oxidant. A barrier of ∼35 kcal mol–1 has been experimentally determined for inversion of configuration in the neutral conjoined bis[5]diazahelicene, while the inversion barriers in its radical cation and diradical Dication were predicted by the DFT computations to be within a few kcal mol–1 of that in the neutral species. Chiral HPLC resolution provides the chiral D2-symmetric conjoined bis[5]diazahelicene, enriched in (P,P)- or (M,M)-enantiomers. The enantiomerically enriched triplet diradical Dication is configurationally st...