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In the rapidly developing field of photovoltaics, organic–inorganic metal halide perovskites are outstanding for their exceptional power conversion efficiencies (PCE), exceeding 26%. However, the full potential of these materials is often undermined by the prevalence of defects within their structure and at the grain surfaces, leading to significant nonradiative recombination losses. To meet this critical challenge, this study introduces a novel strategy involving a pyrrolidinium derivative and tetrafluoroborate ionic liquid, specifically 2‐pyrrolidin‐1‐ium‐1‐ethylammonium tetrafluoroborate (PyE(BF4)2), as an additive in the perovskite precursor. This approach aims to meticulously control crystallization processes and effectively passivate defects on the surface and grain boundaries of the perovskite. The formation of N─H...I− hydrogen bonds and strong ionic interactions, PyE(BF4)2 not only stabilizes the [PbI6]4− framework but also optimizes the valence band alignment with the hole transport layer. Empirical results demonstrate that perovskite solar cells modified with PyE(BF4)2 have achieved a notable PCE of 23.80% and remarkable stability exceeding 1300 h under standard testing protocols (ISOS‐V‐1). The findings emphasize the transformative potential of multifunctional ionic liquids in enhancing the performance and durability of perovskite‐based photovoltaic devices, marking a significant step forward in pursuing sustainable and efficient solar energy solutions. [ABSTRACT FROM AUTHOR]

Mixed halide perovskite nanocrystals show great promise for high-performance light-emitting diodes (LEDs) due to their tunable band gaps, high photoluminescence efficiency, and excellent color purity. However, one major challenge in using mixed halide CsPbBrxCl3–x NCs for pure blue LEDs is the instability of their electroluminescence (EL) caused by halide segregation. Here, we report an effective pseudohalide tetrafluoroborate (BF4–) passivation approach to improve the EL stability of CsPbBrxCl3–x NC-based LEDs. Our approach involves the solution-processed treatment of CsPbBrxCl3–x NCs by the complex of tributylphosphine oxide and calcium tetrafluoroborate, which yields pseudohalide BF4–-passivated CsPbBrxCl3–x NCs. The BF4– fills the surface halide ion vacancy, providing dual benefits of surface passivation and halide migration suppression. By using these BF4–-passivated CsPbBrxCl3–x NCs as the emitting layer, we have successfully fabricated spectrally stable and pure blue LEDs with an emission peak at 468 nm, a maximum luminance of 275 cd/m2, and a maximum external quantum efficiency of 3.2%. Our proposed BF4–-passivated NCs strategy will pave the way for the development of efficient, stable, and pure blue perovskite LEDs. [ABSTRACT FROM AUTHOR]

Abstract Background Sodium iodide symporter (NIS) imaging by positron emission tomography (PET) is gaining traction in nuclear medicine, with an increasing number of human studies being published using fluorine-18 radiolabelled tetrafluoroborate ([18F]TFB). Clinical success of any radiotracer relies heavily on its accessibility, which in turn depends on the availability of robust radiolabelling procedures providing a radiotracer in large quantities and of high radiopharmaceutical quality. Results Here we publish an improved radiolabelling method and quality control procedures for high molar activity [18F]TFB. The use of ammonium hydroxide for [18F]fluoride elution, commercially available boron trifluoride-methanol complex dissolved in acetonitrile as precursor and removal of unreacted [18F]fluoride on Florisil solid-phase extraction cartridges resulted in the reliable production of [18F]TFB on SYNTHRA and TRACERLAB FXFN automated synthesizers with radiochemical yields in excess of 30%, radiochemical purities in excess of 98% and molar activities in the range of 34–217 GBq/µmol at the end of synthesis. PET scanning of a mouse lung tumour model carrying a NIS reporter gene rendered images of high quality and improved sensitivity. Conclusions A novel automated radiosynthesis procedure for [18F]tetrafluoroborate has been developed that provides the radiotracer with high molar activity, suitable for preclinical imaging of NIS reporter gene.

Tetrafluoroborate (BF4−) has long been used as a spectator counter anion. Herein, we report an unprecedented salt metathesis between a variety of BF4− salts and a series of organoboronic acids yielding the corresponding organotrifluoroborates. We identified conditions for fast and efficient fluoridation (<1 h) with minimal workup. Fundamentally, this work discloses the proclivity of BF4− to exchange fluoride atoms with organoboronates, highlighting the lability of BF4−. [ABSTRACT FROM AUTHOR]

Background: Sodium iodide symporter (NIS) imaging by positron emission tomography (PET) is gaining traction in nuclear medicine, with an increasing number of human studies being published using fluorine-18 radiolabelled tetrafluoroborate ([18F]TFB). Clinical success of any radiotracer relies heavily on its accessibility, which in turn depends on the availability of robust radiolabelling procedures providing a radiotracer in large quantities and of high radiopharmaceutical quality. Results: Here we publish an improved radiolabelling method and quality control procedures for high molar activity [18F]TFB. The use of ammonium hydroxide for [18F]fluoride elution, commercially available boron trifluoride-methanol complex dissolved in acetonitrile as precursor and removal of unreacted [18F]fluoride on Florisil solid-phase extraction cartridges resulted in the reliable production of [18F]TFB on SYNTHRA and TRACERLAB FXFN automated synthesizers with radiochemical yields in excess of 30%, radiochemical purities in excess of 98% and molar activities in the range of 34–217 GBq/µmol at the end of synthesis. PET scanning of a mouse lung tumour model carrying a NIS reporter gene rendered images of high quality and improved sensitivity. Conclusions: A novel automated radiosynthesis procedure for [18F]tetrafluoroborate has been developed that provides the radiotracer with high molar activity, suitable for preclinical imaging of NIS reporter gene. [ABSTRACT FROM AUTHOR]

An AgI-based coordination polymer (CP), namely, poly[[[μ3-2-(1,3,5-triaza-7-phosphoniatricyclo[3.3.1.13,7]decan-7-yl)ethanoate-κ4N:N′:O,O′]silver(I)] tetrafluoroborate], {[Ag(C9H16N3O2P)]BF4}n, was synthesized in an aqueous solution of zwitterionic 2-(1,3,5-triaza-7-phosphoniatricyclo[3.3.1.13,7]decan-7-yl)ethanoate (L) and AgBF4 with exclusion of light at room temperature. The colourless and light-insensitive CP crystallized in the monoclinic space group Cc. The asymmetric unit consists of an AgI cation, the zwitterionic L ligand and a BF4− counter-ion. Each AgI ion is coordinated by two carboxylate oxygen atoms in a chelating coordination mode, as well as one of the nitrogen atoms of two neighbouring L ligands. The crystal structure of the CP was classified as a unique three-dimensional arrangement. The CP was also characterized in aqueous solutions by multinuclear NMR and HRMS spectroscopies and elemental analysis.

The crystal and molecular structure of an organic salt, in which a 2,4,6‐trimethylpyrylium cation forms a salt with a tetrafluoroborate anion, namely, 2,4,6‐trimethylpyrylium tetrafluoroborate, C8H11O+·BF4−, has been experimentally realized. The compound crystallizes in the orthorhombic centrosymmetric space group Pnma. The crystal packing is stabilized via a subtle interplay of [F3—B—F]−...O+—C fluorine/oxygen‐centred halogen/chalcogen bonds and Cδ+...Fδ− tetrel‐bonded contacts. Although the O centre has a formal charge of +1, the estimation of the partial negative charges on O is in accordance with electronegativity considerations. Hirshfeld surface analysis, which also includes an analysis of the three‐dimensional deformation density, along with molecular electrostatic potential (MESP) calculations, provides quantitative insights into the nature of the intermolecular interactions. The topological analysis of the electron‐density distribution has been performed using AIMAll and TOPOND, and unequivocally establishes the bonding character associated with the different noncovalent interactions. In addition, NBO analysis and polarizability calculations using PolaBer render deeper physical insights into the electronic characteristics of these noncovalent interactions. [ABSTRACT FROM AUTHOR]

Magnesium and its alloys are widely used in many areas because of their light weight, excellent dimensional stability, and high strength-to-weight ratio. However, the material exhibits poor wear and corrosion resistance, which limits its use. Plasma electrolytic oxidation (PEO) is an effective surface modification method for producing ceramic oxide layers on Mg and their alloys. The influence of the additions of sodium tetrafluoroborate (NaBF4) and sodium fluoride (NaF) into alkaline-silicate electrolyte on the properties of the conversion layers formed in the magnesium AZ91D alloy has been investigated. Surface morphology and chemical composition were determined by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The anticorrosive properties of the layers were evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) methods in simulated body fluid (SBF). The presence of NaBF4 or NaF in the electrolyte increases the corrosion resistance of the protective layer. However, the best anticorrosive properties show the layers obtained in the presence of NaBF4. This is probably caused by the incorporation of boron and fluorine in the form of Mg (BF4)2 mainly in the barrier layer. [ABSTRACT FROM AUTHOR]

Although metal-halide perovskite nanocrystals (NCs) have garnered significant attention for optoelectronic applications, the presence of electrically insulating organic ligands in CsPbBr 3 NCs hinders efficient charge injection and transportation in light-emitting diodes (LEDs). A common approach to address this issue involves ligand exchange with shorter ligands and precise control of the surface ligand density through additional purification steps. Nevertheless, the practical application of these methods has been hindered by their poor structural integrity and high surface-defect density, which remain a challenge. Our investigation reveals that NOBF 4 treatment effectively replaces native ligands with BF 4 - anions, in which BF 4 - anions are readily coordinated with the positively charged CsPbBr 3 surface metal centers, thereby improving the photoluminescence quantum yield (PLQY) and thermal stability. In particular, the presence of BF 4 - anions coordinated at CsPbBr 3 surfaces efficiently suppresses the pathway of excitons toward thermally activated nonradiative recombination, leading to minimal thermal quenching and superior device performance in green-emitting PeLEDs. Notably, PeLEDs based on CsPbBr 3 NCs with the reconstructed surface via NOBF 4 treatment exhibit an improved current efficiency of 31.12 cd/A and an external quantum efficiency of 11.24%, increased by 2.8 times compared to that of the pristine sample, indicating the enhanced hole-electron injection and transport into the CsPbBr 3 NCs. Therefore, our results highlight the potential of NOBF 4 as a versatile reagent for the ligand exchange and surface passivation of CsPbBr 3 NCs, thereby offering promising prospects for the development of stable, high-performance PeLEDs.

The reaction of copper(II) tetrafluoroborate with dimethylglyoxime (H2dmg) leads to the formation of the dinuclear complexes [Cu2(dmg)(Hdmg)(EtOH)(H2dmg)]BF4 (1) and [Cu2(dmg ⋅ BF2)(Hdmg)(H2dmg)]BF4 (2). In 2, BF2 deriving from BF4− has been inserted into the oxime groups to form an O,O‐bidentate difluoroboron complex. Co‐crystallization of 1 and 2 impeded a thorough characterization of 2. In further attempts to prepare pure 2, the difluoroboron complexes [Cu(dmg ⋅ BF2)2(MeCN)] (3) and [Cu(dmg ⋅ BF2)(Hdmg)] (4) have been obtained. Attempts to isolate the BF2‐bridged ligand failed. Even though BF4− readily is decomposed to formally form BF2+ that is inserted into the resulting complexes and F−, the nascent F− ions are not a suitable F− source for organic fluorination reactions. Nevertheless, the described, facile route to prepare O,O‐bidentate difluoroboron complexes without the usage of the highly toxic BF3 ⋅ OEt2 but BF4− instead is of interest for synthetically working chemists. [ABSTRACT FROM AUTHOR]

With the extensive application of task-specific ionic liquids (TSILs), their environmental impact has attracted increasing attention. However, no studies involving residue analyses of TSILs have been reported in the literature thus far. In the present study, residues of four TSILs ([C2NH2MIm]BF4, [HOEMIm]BF4, [HOEMIm]NO3, [MOEMIm]BF4) were analyzed by high-performance liquid chromatography–tandem mass spectrometry. The limit of detection of instrument was approximately 10−15 g. Residual TSILs were extracted from soil and plant samples by the accelerated solvent extraction method. In water, soil and plants, the coefficient of variation was 0.38%–4.43%, and the method detection limits of the four TSILs were lower than 1.40 ng g−1. These results meet the standards of residue analysis. The present study can provide an analysis method for studying TSIL residues and toxicity in the environment. [ABSTRACT FROM AUTHOR]

Epoxides are frequently used in coatings due to their great adhesion to most materials, high resistance towards chemicals and well‐defined material properties. Onium salts such as iodonium and sulfonium salts are one of the most widespread classes of initiators used in light‐induced cationic polymerization of such epoxides. We successfully synthesized onium salts based on group 14 to 16 elements in the periodic table. They were then characterized using cyclic voltammetry and UV–visible spectroscopy before determining their reactivity in epoxy‐based resins. Using commercial bisphenol‐A‐based resins, thiopyrylium, bismuithonium and pyrylium salts show good reactivity and epoxy group conversions above 60% in simultaneous thermal analysis. Photochemically interesting new cationic initiators were identified to be oxonium, thiopyrylium and selenonium salts. Additionally, bismuthonium and stibonium salts show great potential towards sensitization with anthracene. © 2021 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

An AgI-based coordination polymer (CP), namely, poly[[[μ3-2-(1,3,5-tri­aza-7-phospho­niatri­cyclo­[3.3.1.13,7]decan-7-yl)ethano­ate-κ4N:N':O,O']silver(I)] tetra­fluoro­borate], {[Ag(C9H16N3O2P)]BF4}n, was synthesized in an aqueous solution of zwitterionic 2-(1,3,5-tri­aza-7-phospho­niatri­cyclo­[3.3.1.13,7]decan-7-yl)ethan­o­ate (L) and AgBF4 with exclusion of light at room temperature. The colourless and light-insensitive CP crystallized in the monoclinic space group Cc. The asymmetric unit consists of an AgI cation, the zwitterionic L ligand and a BF4- counter-ion. Each AgI ion is coordinated by two carboxyl­ate oxygen atoms in a chelating coordination mode, as well as one of the nitro­gen atoms of two neighbouring L ligands. The crystal structure of the CP was classified as a unique three-dimensional arrangement. The CP was also characterized in aqueous solutions by multinuclear NMR and HRMS spectroscopies and elemental analysis. [ABSTRACT FROM AUTHOR]

The new organic salt m-xylylenediaminium bis (tetrafluoroborate) monohydrate was prepared from a mixture of an aqueous solution of tetrafluoroborate acid and m-xylylenediamine. Crystals were grown by slow evaporation method and characterized by single-crystal X-ray diffraction. It crystallizes in the monoclinic system, space group P21/c, with a = 5.4839(2), b = 10.9453(3), c = 23.0760(6) Å, β = 95.105(1)°, V = 1379.59(14) Å3 and Z = 4. The intermolecular interactions were identified by Hirshfeld Surfaces analysis and their associated 2D fingerprint plots. Photoluminescence and UV–Vis absorption were carried out to identify optical properties and determine the energy gap. Dielectric and conduction mechanism were studied at different frequencies, in the temperature range of 303–390 K. A comparison of the optimized structure at the B3LYP/6-311++G(2d,2p) level, using the density functional theory, was made with the experimentally determined structure. Comprehensive experimental and theoretical structural studies were carried out by FT-IR. Molecular electrostatic potentials were also studied and discussed. [ABSTRACT FROM AUTHOR]

Introduction: Efficient therapy of recurrent differentiated thyroid cancer (DTC) is dependent on precise molecular imaging techniques targeting the human sodium iodide symporter (hNIS), which is a marker both of thyroid and DTC cells. Various iodine isotopes have been utilized for detecting DTC; however, these come with unfavorable radiation exposure and image quality ([131I]iodine) or limited availability ([124I]iodine). In contrast, [18F]tetrafluoroborate (TFB) is a novel radiolabeled PET substrate of hNIS, results in PET images with high-quality and low radiation doses, and should therefore be suited for imaging of DTC. The aim of the present study was to compare the diagnostic performance of [18F]TFB-PET to the clinical reference standard [131I]iodine scintigraphy in patients with recurrent DTC. Methods: Twenty-five patients with recurrent DTC were included in this retrospective analysis. All patients underwent [18F]TFB-PET combined with either CT or MRI due to newly discovered elevated TG levels, antiTG levels, sonographically suspicious cervical lymph nodes, or combinations of these findings. Correlative [131I]iodine whole-body scintigraphy (dxWBS) including SPECT-CT was present for all patients; correlative [18F]FDG-PET-CT was present for 21 patients. Histological verification of [18F]TFB positive findings was available in 4 patients. Results: [18F]TFB-PET detected local recurrence or metastases of DTC in significantly more patients than conventional [131I]iodine dxWBS and SPECT-CT (13/25 = 52% vs. 3/25 = 12%, p = 0.002). The diagnosis of 6 patients with cervical lymph node metastases that showed mildly increased FDG metabolism but negative [131I]iodine scintigraphy was changed: [18F]TFB-PET revealed hNIS expression in the metastases, which were therefore reclassified as only partly de-differentiated (histological confirmation present in two patients). Highest sensitivity for detecting recurrent DTC had the combination of [18F]TFB-PET-CT/MRI with [18F]FDG-PET-CT (64%). Conclusion: In the present cohort, [18F]TFB-PET shows higher sensitivity and accuracy than [131I]iodine WBS and SPECT-CT in detecting recurrent DTC. The combination of [18F]TFB-PET with [18F]FDG-PET-CT seems a reasonable strategy to characterize DTC tumor manifestations with respect to their differentiation and thereby also individually plan and monitor treatment. Future prospective studies evaluating the potential of [18F]TFB-PET in recurrent DTC are warranted. [ABSTRACT FROM AUTHOR]

Abstract Background 18F-Tetrafluoroborate (18F-TFB) is a promising iodide analog for PET imaging of thyroid cancer and sodium/iodide symporter (NIS) reporter activity in viral therapy applications. The aim of this study was to evaluate the safety, pharmacokinetics, biodistribution, and radiation dosimetry of high-specific activity 18F-TFB in healthy human subjects. Methods 18F-TFB was synthesized with specific activity of 3.2 ± 1.3 GBq/μmol (at the end of synthesis). Dynamic and whole-body static PET/CT scans over 4 h were performed after intravenous administration of 18F-TFB (333–407 MBq) in four female and four male healthy volunteers (35 ± 11 years old). Samples of venous blood and urine were collected over the imaging period and analyzed by ion-chromatography HPLC to determine tracer stability. Vital signs and clinical laboratory safety assays were measured to evaluate safety. Results 18F-TFB administration was well tolerated with no significant findings on vital signs and no clinically meaningful changes in clinical laboratory assays. Left-ventricular blood pool time-activity curves showed a multi-phasic blood clearance of 18F-radioactivity with the two rapid clearance phases over the first 20 min, followed by a slower clearance phase. HPLC analysis showed insignificant 18F-labeled metabolites in the blood and urine over the length of the study (4 h). High uptakes were seen in the thyroid, stomach, salivary glands, and bladder. Urinary clearance of 18F-TFB was prominent. Metabolic stability was evidenced by low accumulation of 18F-radioactivity in the bone. Effective doses were 0.036 mSv/MBq in males and 0.064 mSv/MBq in females (p = 0.08, not significant). Conclusions This initial study in healthy human subjects showed 18F-TFB was safe and distributed in the human body similar to other iodide analogs. These data support further translational studies with 18F-TFB as NIS gene reporter and imaging biomarker for thyroid cancer and other disease processes that import iodide.

Objective: To optimize the ionic liquid based microwave-assisted extraction (IL-MAE) of polyphenolic content from Peperomia pellucida (L) Kunth. Methods: The IL-MAE factors as experimental design parameters, including microwave power, extraction time, ionic liquid concentration, and liquid–solid ratio had been involved. Response surface methodology and Box–Behnken design were used to obtain predictive model (multivariate quadratic regression equation) and optimization of the extraction process. The response surface was analyzed by using the yields of total polyphenolic content as response value. Results: Based on the obtained results the optimum extraction condition, including microwave power of 30% Watts, extraction time of 18.5 min, the ionic liquid concentration of 0.79 mol/L, and the liquid–solid ratio of 10.72 mL/g 1-Buthyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) as a solvent was selected. The regression model was obtained to predicts the yields from Peperomia pellucida: Y = 30.250 – 1.356X1 + 2.655X2 + 2.252X3 – 0.565X4 + 0.990 X1X3 – 8.172 X1X4 – 3.439 X3X4 – 4.178 X12 – 3.210 X32 – 6.786 X42 – 7.290 X12X3 + 5.575 X1X32 – 4.843 X32X4 with R2 = 0.82519. Scale-up confirmation test was obtained the maximum yields of total polyphenolics content with the amount of 31.172 5 μg GAE/g. Conclusions: The IL-MAE method produced a higher extraction polyphenolic and performed rapidly, easily and efficiently.

Kinetically facile intercalation of anions into graphite electrodes is essential for the good performance of dual‐ion batteries. The intercalation of BF4− anions into graphite electrodes is found to be strongly impeded in the electrolyte of 1.25 m LiBF4−ethylmethyl carbonate. For this, both the strong attraction between Li+ and BF4− clusters and the special solvation state of the anion are to blame. Two strategies are employed to tailor the solvation states of ions in the solutions, which prove easy and effective in facilitating anion intercalation into graphite electrodes. [ABSTRACT FROM AUTHOR]

The solvation of the Ag+ ion in the 1-butyl-3-methylimidazolium tetrafluoroborate ([C 4 mim][BF 4 ]) ionic liquid (IL) has been studied by means of experimental and theoretical methods with the aim of elucidating the cation coordination structure and thermodynamic properties. Car-Parrinello molecular dynamics (CPMD) simulations showed that the Ag+ ion is coordinated by an average number of four [BF 4 ]− anions in a pseudo-tetrahedral geometry. A high configurational disorder of the first solvation sphere is found, where the anions can be found both in mono- and bidentate coordination mode around the Ag+ ion. Also, a solvational equilibrium is observed as due to [BF 4 ]− anion dissociation along the trajectory. The analysis of X-ray absorption spectroscopy data confirmed the picture provided by the CPMD simulation. Classical molecular dynamics simulations were carried out to obtain the single-ion solvation thermodynamic parameters. The negative water → IL free energy of transfer suggests that the Ag+ ion is more favorably solvated in the [C 4 mim][BF 4 ] IL than in water. This behavior is due to a balance between the enthalpic and entropic contributions, which allows to find a rationale to the strong solvation capabilities of BF 4 -based ILs towards Ag+. • The coordination environment and solvation thermodynamics of the Ag+ ion the [C 4 mim][BF 4 ] ionic liquid are analyzed. • CPMD simulations show that the Ag+ ion is coordinated by four [BF 4 ]− anions in a tetrahedral geometry. • XAS data confirm the local structure around the Ag+ ion and a high configurational disorder of the solvation sphere. • Ag+ ion is more favorably solvated in [C 4 mim][BF 4 ] than in water. [ABSTRACT FROM AUTHOR]

Two new nonmetal cation tetrafluoroborate phases [H3tren](BF4)3 (I) and [H3tren](BF4)3 HF (II) were synthesized by microwave-assisted solvothermal and characterized by single crystal X-ray diffraction, IR spectroscopy and thermal analysis DTA-TGA. [H3tren](BF4)3 is cubic (P213) with unit cell parameter a = 11.688(1) Å. [H3tren](BF4)3•HF is trigonal (R3c) with unit cell parameters a = 15.297(6) Å and c = 12.007(2) Å. Both (I) and (II) structures can be described from isolated tetrafluoroborate BF4- anions, triprotonated tris-(2-aminoethyl)amine (tren) [H3tren]3+. Phase (II) contains disordered BF4- tetrahedron and hydrofluoric acid.

[Display omitted] • Evaporation and decomposition are competing processes during heating of BMImBF 4 ionic liquid. • Vapor composition of the ionic liquid is complex and depends significantly on evaporation conditions. • Evaporation of decomposition products is kinetically hindered. Thermodynamic properties of evaporation of 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMImBF 4) ionic liquid (IL) were determined by Knudsen effusion mass spectrometry. Heating of this compound is accompanied by competing evaporation and decomposition. Interpretation of mass spectrum was carried out by the analysis of data obtained for different evaporation conditions: i) Knudsen cell with a small effusion orifice, ii) open Knudsen cell, and iii) open surface of IL. It was revealed that at non-equilibrium Langmuir conditions BMImBF 4 IL evaporates congruently practically only in the form of neutral ion pairs (NIPs). In equilibrium conditions, decomposition products prevail in vapor with only about 7 % vapor fraction of NIPs. The main route of IL decomposition is the formation of substituted imidazole‐2‐ylidene (C 8 N 2 H 14 BF 3) and hydrofluoric acid (HF). The mass spectrum of C 8 N 2 H 14 BF 3 was obtained by the analysis of a distillate collected during evaporation in the Knudsen cell. The decomposition products, due to their high volatility, do not accumulate practically in the liquid phase and hence the activity of IL may be considered to be 1. This circumstance makes it possible to perform the thermodynamic calculations for the IL evaporation reaction. The temperature dependence of the NIPs' vapor pressure, ln(p /Pa) = (–13.806 ± 0.252)∙103/ T + (23.443 ± 0.519), was used to obtain the vaporization enthalpy, Δ v H °(298.15 K) = 138 ± 5 kJ·mol−1, by the methods of the second and third laws. The formation enthalpy of BMImBF 4 NIPs, Δ f H °(298.15 K) = −1084 ± 15 kJ·mol−1, was found from combination of the vaporization enthalpy and the formation enthalpy of IL. The vapor composition over BMImBF 4 under equilibrium conditions was computed. It was demonstrated that decomposition of IL is kinetically hindered so the studied system is characterized by a partial equilibrium. [ABSTRACT FROM AUTHOR]