N. S. Chilingarov

Electron affinity of rhodium tetrafluoride

Knudsen-cell mass spectrometry was used for the investigation of ion-molecule equilibria in the gas phase of some fluoride systems. The combined ion source used allows the partial pressures of negative ions and neutral molecules to be measured within the scope of one experiment. By the third law of thermodynamics the following quantities at T = 298.15 K have been determined: FeF4−(g)=FeF3(g)+F−(g); ΔrHm°=(456.1±13.7)kJ·mol−1 ; MnF4−(g)=MnF3(g)+F−(g); ΔrHm°=(421.0±13.0)kJ·mol−1 ; RhF4−(g)=RhF3(g)+F−(g); ΔrHm°=(400.8±14.4)kJ·mol−1 ; RhF4−(g)=RhF3(g)+F(g); ΔrHm°=(248.0±15.0)kJ·mol−1 ; ΔfHm°(FeF4−,g)=−(1475.2±15.2)kJ·mol−1 ; ΔfHm°(MnF4−,g)=−(1462.7±60.0)kJ·mol−1 ; (EaRhF4)=(482±19)kJ·mol−1 ;

Mass Spectrometry Study of C60 and C60-NiF2 Fluorination with Molecular Fluorine

Abstract Fluorination of [60]fullerene and [60]fullerene-NiF2(s) has been studied in situ by Knudsen cell mass spectrometry with admission of molecular fluorine. The fluorination processes were controlled in the temperature range 500 − 800 K at molecular fluorine pressure 10−4 − 10−5 atm. Temperature, time of fluorination and fluorine pressure were varied during the investigation. It was found that variation of these parameters did not lead to the selective fluorination. It was shown that NiF2(s) significantly influences the composition of the product mixture: a large amount of nickel difluoride in the system suppresses the fluorination reaction while the presence of a small amount promotes the selective fluorination. C60Fi18 (50% in the gas phase) was produced in our experiments under the following conditions: 20 h, 720 K, P(F2) = 2 10−4 atm in the prefluorinated (inner surface covered with NiF2(s) layer) Ni-reactor. An important point of the study was verification of the thermodynamic equilibrium in the...

Thermochemistry of gaseous gold trifluoride by knudsen cell mass spectrometry

Knudsen cell mass spectrometry was used to study the equilibrium vapour in the AuXeF2MnF3 system. A combined ion source made it possible to determine constants of molecular/molecular and ion/molecular equilibria. The enthalpies ΔrH298 K0 (kJ mol−1) were determined for the reactions

Mass spectrometric studies of 1-ethyl-3-methylimidazolium and 1-propyl-2,3-dimethylimidazolium bis(trifluoromethyl)-sulfonylimides

RATIONALE Ionic liquids ([Cat(+)][An(-)]) were believed to decompose before reaching vaporization temperatures, but recently some of them have been shown to vaporize congruently. Low-temperature vaporization of ionic substances is an intriguing phenomenon, so the vapor-phase composition and reactions of ionic liquids deserve more extensive study. METHODS Evaporation of two ionic liquids, [C2MIM(+)][Tf2 N(-)] and [C3MMIM(+)][Tf2N(-)], was studied by means of Knudsen effusion mass spectrometry. These liquids were also characterized using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, UV/Vis, IR, NMR spectroscopy, and elemental analysis. RESULTS The vaporization enthalpies of (118 ± 3) and (124 ± 2) kJ·mol(-1) were determined for [C2MIM(+)][Tf2N(-)] and [C3MMIM(+)][Tf2N(-)], respectively. The corresponding equations for their saturated vapor pressures are: ln(p{[C2MIM(+)][Tf2N(-)]}/Pa) = -(14213 ± 325)/(T/K) + (26.57 ± 1.04), ln(p{[C2MMIM(+)][Tf2N(-)]}/Pa) = -(14868 ± 221)/(T/K) + (27.19 ± 0.60). The MALDI studies (positive and negative ion modes) enabled detection of monomeric [Cat(+)] and [An(-)] ions, the cluster ions {[Cat(+)]2 [An(-)]}(+) and {[Cat(+)][An(-)]2}(-), and some complex anions {2[An(-)] + Na(+)}(-), {2[An(-)] + K(+)}(-), {2[An(-)] + Cu(+)}(-) and {3[An(-)] + Ca(2+)}(-). CONCLUSIONS Knudsen effusion mass spectrometry proved to be a valuable method to study the thermodynamics of ionic liquids. The saturated vapor pressure and vaporization enthalpy of [C3MMIM(+)][Tf2N(-)] were accurately determined for the first time. MALDI is also capable of providing indirect information on hydrogen bonding.

Mass spectrometric and FTIR spectroscopic identification of FeF4 molecules in gaseous phase

Abstract The existence of a new compound – gaseous FeF4 – was assumed based on the results of Knudsen effusion mass spectrometry and FTIR spectroscopy. Hyperfluorination was achieved by applying excessive amount of CeF4(s) fluorinating agent in reaction with FeF3(s) at high temperatures (T=930–1050 K). The 758.5 cm−1 vibrational frequency was attributed to the Fe–F stretching mode of argon isolated FeF4 molecules.

In situ time-resolved X-ray diffraction study of manganese trifluoride thermal decomposition

Abstract The first in situ time-resolved X-ray diffraction study of MnF3 crystal structure evolution during its thermal decomposition was performed on the GILDA beam line at the European Synchrotron Radiation Facility (ESRF, France). Mn2F5(s) was observed as intermediate phase during the process of decomposition of MnF3(s) to MnF2(s).

Enthalpy of formation of platinum hexafluoride

Abstract Knudsen-cell mass spectrometry was used for the investigation of the gas-phase equilibrium: PtF 4 + F 2 = PtF 6 , generated within an effusion cell by heating a (Pt + TbF 4 ) mixture. By use of the third law the following quantities at T = 298.15 K have been determined: Δ r H m o = −(152 ± 12) kJ·mol −1 ; Δ f H m o (PtF 6 , g) = −(676 ± 28) kJ·mol −1 ; Δ f H m o (PtF 6 , s, I) = −(714 ± 28) kJ·mol −1 ; Δ f H m o (PtF 6 , s, II) = −(722 ± 28) kJ·mol −1 .

MASS SPECTROMETRIC DETERMINATION OF COBALT TRIFLUORIDE SATURATED VAPOR PRESSURE. ENTHALPY OF FORMATION OF GASEOUS COF4 AND COF4

Knudsen cell mass spectrometry has been used for measuring the saturated vapor pressure of cobalt trifluoride. Enthalpy of sublimation of cobalt trifluoride, ΔSH0(CoF3,0 K), has been determined as 213.7±11.0 kJ/mol. Enthalpies of formation of the gaseous molecules CoF3, CoF4, and of the anion CoF4−, ΔfH0(0 K), have been recalculated as −572.3±32.0, −649.0±32.3 and −1265.3±40.6 kJ/mol, respectively. The electron affinity of cobalt tetrafluoride, EA(COF4), was found to be 6.4±0.3 eV.

Use of superionics for studying complex negative ions in vapors of nonvolatile compounds

The effect of cerium trifluoride on the ion emission in the KF-K3AlF6 system is studied by high-temperature mass spectrometry. It is shown that negative ions’ signals are absent when the system is evaporated from a clean Knudsen nickel cell. The ions are only detected after the long-term heating of the KF-K3AlF6 system or the preliminary annealing of CeF3. The results are explained by the formation in the cell of a salt layer with high anionic conduction induced by either KF or CeF3, respectively.

Fluorinated microwave exfoliated graphite oxide: structural features and double layer capacitance

ABSTRACT Fluorinated microwave exfoliated graphite oxide (MEGO) samples containing 5.7–29.3 at.% of fluorine were prepared by gas phase treatment of MEGO with XeF2. According to X-ray photoelectron spectroscopy and infrared spectroscopy data, fluorination of MEGO occurs at C=C bonds while leaving the oxygenated domains intact, and increases the O/C ratio. Cyclic voltammetry studies of fluorination effect on double layer capacitance of MEGO shows 67% growth of its specific capacitance, making such and related carbon materials prospective for supercapacitor applications.