Search results for "Dication"
showing 10 items of 733 documents
Metachromatic behavior of methylorange in the presence of ionenes
1994
The addition of different ionenes, polycations with defined structure and charge distances, to methylorange1 in very dilute solutions of water resulted in an observable shift of the absorption maxima from 464 nm to shorter wavelengths. The extent of this so-called metachromasy effect was found to be dependent on the nature of the hydrophobic unit of the polymer backbone. The comparison of UV/VIS spectra's of these solutions with the absorption of a film of a model substance — a dication with methylorange as counteranion — lead to the conclusion that ionenes undergo an exchange of the counteranions when added to a dilute solution of methylorange. Precipitation is slowed down, but the absorpt…
Weak interactions between resorcinarenes and diquaternary alkyl ammonium cations
2005
The interactions of resorcin[4]arenes 1 with alkyl ammonium cations bearing a 1,4-diazabicyclo[2.2.2]octane (DABCO) scaffold (32+, 42+ and 52+) were analyzed in the solid state by X-ray crystallography, in solution by 1H NMR spectroscopy, and in the gas phase by ESI-TOF mass spectrometry. The results are complemented with AM1 calculations and compared to previous reports on complexation studies of resorcinarenes with quaternary alkyl ammonium cations. The NMR titration results indicate that there are hardly any differences in the binding of the quaternary tetramethyl ammonium cation 2+ and the diquaternary N,N’-dimethyl DABCO dication 42+. The large N,N’-dibenzyl DABCO dication 52+ has two …
A Study by Spectroelectrochemical FTIR and Density Functional Theory Calculations of the Reversible Complexing Ability of an Electroactive Tetrathiaf…
2006
We report on the study of the electrochemically targeted complexation/expulsion of a metal cation (Ba2+) by a crown ether tetra(thiomethyl)tetrathiafulvalene derivative (crown-TTM-TTF). Real time, in situ FTIR spectroelectrochemistry was used to obtain spectroscopic evidence of this electrochemically triggered phenomenon. Density functional theory calculations allowed the spectral information collected to be assigned. Both experimental and theoretical results clearly show that neutral crown-TTM-TTF complexes well Ba2+. Complexation is evidenced by a significant downshift of the frequency corresponding to the asymmetric stretching of the C-O-C ether groups. Concerning the cation crown-TTM-TT…
Effect of Protonated Organic Cations and Anion−π Interactions on the Magnetic Behavior of Hexabromorhenate(IV) Salts
2015
Two novel Re-IV compounds of formula (Hbpym)(2)[(ReBr6)-Br-IV]center dot 4H(2)O (1) and (H(4)biim)[(ReBr6)-Br-IV]center dot 4H(2)O (2) [Hbpym(+) = 2,2'-bipyrimidinium cation and H(4)biim(2+) = 2,2'-biimidazolium dication] have been prepared and magnetostructurally characterized. 1 and 2 exhibit distinct crystal packing, and the presence of weak intermolecular contacts, such as Re-Br...B-rRe (1 and 2), Re-Br center dot center dot center dot(H2O)center dot center dot center dot BrRe (1 and 2), and Re-Br center dot center dot center dot pi center dot center dot center dot Br-Re (2), lead to different magnetic behaviors. While 1 is antiferromagnetic, 2 is a ferromagnetic compound and indeed the…
The First Examples of a Crown Ether Intramolecularly Encapsulating Mono- and Diorganotin Dications: Synthesis and Structures of [PhSnCH2([16]crown-5)…
2010
The reaction of silver perchlorate with [PhI 2 SnCH 2 ([16]crown-5)] (1) and [I 3 SnCH 2 ([16]crown-5)] (2) gave the organotin(IV)-substituted crown ether complexes [PhSnCH 2 ([16]crown-5)][ClO 4 ] 2 (3) and [HOSnCH 2 ([16]crown-5)][Y] 2 (4: Y= ClO 4 , 5: Y=CF3 S 03 ) , respectively. All compounds have been isolated as air-stable materials and characterised by 1 H, 13 C, 119 Sn and 119 Sn MAS (5) NMR spectroscopy, ESIMS spectrometry, elemental analysis and by single-crystal X-ray diffraction analysis. The molecular structures of 3-5 show that the tin(IV) cation fits perfectly into the crown ether cavity and is coordinated by the five oxygen atoms of the ring to give a pentagonal bipyramidal…
A new type of pi-electron donors with one dithiole unit: Substituted 7-(1,3-dithiol-2-ylidene)-7-hydrobenz[d,e]anthracenes
1999
New electron donors 11a–c bearing only one 1,3-dithiole ring conjugated with an acene backbone have been synthesized by Wittig–Horner reactions from 7H-benz[d,e]anthracen-7-one (10) and differently substituted phosphonate esters 9a–c. The donor properties of 11 have been characterized by means of both experimental techniques and quantum chemical calculations. Cyclic voltammetry measurements on the novel compounds predict donor abilities comparable to those of TTF and BEDT-TTF. The voltammograms show a multi-stage redox behaviour with oxidation up to the trication, where the first two oxidation processes take place at very close potentials. These processes have been assigned to a simultaneou…
Cathodic behaviour of dicationic imidazolium bromides: the role of the spacer
2019
The cathodic reduction of dicationic imidazolium bromides, whose spacer is either an aliphatic chain or a xylyl group, leads to the formation of the corresponding N-heterocyclic carbenes (NHCs), which were isolated as the corresponding thiones, after reaction with elemental sulfur. The behaviour of the dications was compared with the corresponding monocations. The behaviour of dicarbenes depends on the nature of the spacer. This study evidenced that dicarbenes deriving from xylyl dications are less stable than the corresponding aliphatic ones (giving lower yields in thiones), due to a debenzylation reaction. On the other hand, the yields in thiones starting from aliphatic dications are high…
Revindication of religious organizations’ properties in Poland : Thirty years’ experience of building a democratic state ruled by law
2022
Celem tego artykułu jest analiza przepisów, na mocy których odbywa się w Polsce po 1989 r. rewindykacja nieruchomości osób prawnych związków wyznaniowych upaństwowionych w okresie Polski Ludowej. Omówiono w nim zarówno tryby, jak i sposoby regulacji spraw majątkowych wyznaniowych osób prawnych, uwzględniając liczne zmiany stanu prawnego wprowadzane kolejnymi nowelizacjami przepisów oraz ewolucję ich wykładni dokonywanej przez judykaturę i doktrynę. Zwrócono szczególną uwagę na dyskusyjne kwestie prawne, w tym na nieuprawnione zróżnicowanie sytuacji prawnej poszczególnych związków wyznaniowych. Przeprowadzone w artykule analizy prowadzą do wniosku, że ustawodawca konsekwentnie uwłaszczył wsz…
Etudier la dimension communciationnelle des religions
2014
International audience
Critical limb ischaemia: definition and natural hystory
2004
The term critical limb ischemia refers to a condition characterized by chronic ischemic at-rest pain, ulcers, or gangrene in one or both legs attributable to objectively proven arterial occlusive disease. Critical limb ischemia implies chronicity and is to be distinguished from acute limb ischemia. Its incidence is approximately 500 to 1000 per million year, with the highest rates among older subjects, smokers and diabetics. The rate of primary amputation ranges from 10% to 40%, and was performed only when no graftable distal vessels were present, or in neurologically impaired or hopelessly nonambulatory patients. Contrarily, in some highly specialized and aggressive centres about 90% of pa…