RESUMEN
The gas-phase reactions of noble gas (Ng) cations, namely Kr+ and Xe+, with SF6 were investigated experimentally by Fourier transform ion cyclotron resonance mass spectrometry and computationally using RI-MP2 and BCCD(T) methods. The study revealed a new interaction between Kr+ and neutral SF6 that gave rise to a new cationic, weakly bound complex of Kr, [KrSF5]+, although the major reaction channel was dissociative electron transfer to yield SF5+ and {Kr, F}. Experimental studies examined the formation and stability of the new species and computational studies addressed the energetics of the reaction and indicated that [KrSF5]+ is stable by ca. 1 kcal mol-1. The same computational approach was used to examine the reaction of Xe+ with SF6 and showed it to be thermodynamically unfavourable by ca. 35 kcal mol-1, confirming the non-observation of reaction in the mass spectrometry experiments. An analysis of the bonding in [KrSF5]+ clearly showed that it is a non-covalently bound species, while in its presumed precursor [KrSF6]+ a partially covalent Kr-F bond is present.
RESUMEN
Electrocrystallization from solutions of the dissymmetrical ET derivative cyanobenzene-ethylenedithio-tetrathiafulvalene (CNB-EDT-TTF) in the presence of triiodide I3- affords two different polymorphs (ßâ³ and κ) with the composition (CNB-EDT-TTF)4I3, both with a bilayer structure of the donors. These polymorphs differ in the packing patterns (ßâ³- and κ-type) of the donor molecules in each layer, in both cases with bifurcated C-N···H interactions effectively coupling head-to-head donor molecules between layer pairs. Two ßâ³ polymorphs can be obtained with different degrees of anionic ordering. In one disordered phase, ßâ³d, with a smaller unit cell, the triiodide anions are disordered over two possible positions in a channel between the donor bilayers, while in the ordered phase, ßâ³o, the triiodide anions occupy only one of those positions in this channel, leading to the doubling of the unit cell in the layer plane. These results for ßâ³ phases contrast with the κ polymorph previously reported, for which weaker disorder of the triiodide anions, over two possible orientations with 94 and 6% occupation factors, was observed. While the ßâ³ polymorphs remains metallic down to 1.5 K with a ρ300K/ρ4K resistivity ratio of 250, the κ polymorph presents a much smaller resistivity ratio in the range of 4-10 and superconductivity with an onset temperature of 3.5 K.
RESUMEN
A dissymmetric TTF-type electron donor, cyanobenzene-ethylenedithio-tetrathiafulvalene (CNB-EDT-TTF), was obtained in high yield, by a cross-coupling reaction with triethyl phosphite between 2-thioxobenzo[d][1,3]dithiole-5-carbonitrile and 5,6-dihydro-[1,3]dithiolo[4,5-b][1,4]dithiin-2-one. This new donor was characterized namely by single crystal X-ray diffraction, cyclic voltammetry, NMR, UV-visible and IR spectroscopy.
RESUMEN
The electrocrystallization from solutions of cyanobenzene-ethylenedithio-tetrathiafulvalene (CNB-EDT-TTF) in the presence of different anions X = ClO4(-), PF6(-), and I3(-), affords a new type of 2D molecular metals with composition (CNB-EDT-TTF)4X based on an unprecedented bilayer structure of the donors induced by effective head to head interdonor interactions through the nitrile groups, which is responsible for 2D metallic systems with unusual properties such as the higher band filling, larger effective mass of carriers, and almost degenerated double Fermi surfaces.
