Publications

Abstract The effect of the anion on the electrical conductivity of ionic liquids was explored by a high-precision study of the temperature dependence (283–333 K) of the electrical conductivity of ten ILs based on the 1-butyl-3-methylimidazolium cation, [C4C1im]+. The following trend was observed for the molar conductivity at the reference temperature of 298.15 K: Ac < PF6− < BETI < OTf < TFA < BF4− < FAP < NTf2 < FSI < DCA. The molar conductivity at infinite temperature, AΛ, and the energy barrier, EΛ, derived from the Vogel–Fulcher–Tammann equation (VFT) fitting were found to correlate well with the shape/size/dynamics and cohesive energy/charge localization of the studied ions. An extensive revision and comparison with the available experimental electrical conductivity data for the studied ionic liquids is also presented. Additionally, this work presents a detailed description, testing, and evaluation of performance results of a new system/methodology for the high-precision measurement of the electrical conductivity of ionic fluids, designed to minimize the size of the ionic liquid sample and in situ degassing of the sample. The measuring system is based on a high-precision LCR meter and a conductivity cell system designed to ensure the vacuum and gastightness of the sample container. The high-precision temperature control is ensured by a customized thermal chamber based on a heating and cooling Peltier system. The electrical conductivity data were corrected for the effect of solution polarization by extrapolating the resistance to infinite frequency. The accuracy and resolution of the system were evaluated by measuring the conductivity of the reference ionic liquid, [C6C1im][NTf2] which was found to be in excellent agreement with the recommended data. © 2025 The Author(s)

Abstract Thin films of ionic liquids (ILs) have gained significant attention due to their unique properties and broad applications. Extensive research has focused on studying the influence of ILs' chemical composition and substrate characteristics on the structure and morphology of IL films at the nano- and mesoscopic scales. This study explores the impact of carbon-coated surfaces on the morphology and wetting behavior of a series of alkylimidazolium-based ILs. Specifically, this work investigates the effect of carbon coating on the morphology and wetting behavior of short-chain ([C(2)C(1)im][NTf2] and [C(2)C(1)im][OTf]) and long-chain ([C(8)C(1)im][NTf2] and [C(8)C(1)im][OTf]) ILs deposited on indium tin oxide (ITO), silver (Ag), and gold (Au) substrates. A reproducible vapor deposition methodology was utilized for the deposition process. High-resolution scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy were used to analyze the morphological and structural characteristics of the substrates and obtained IL films. The experimental data revealed that the IL films deposited on carbon-coated Au substrates showed minor changes in their morphology compared to that of the films deposited on clean Au surfaces. However, the presence of carbon coatings on the ITO and Ag surfaces led to significant morphological alterations in the IL films. Specifically, for short-chain ILs, the carbon film surface induced 2D growth of the IL film, followed by subsequent island growth. In contrast, for long-chain ILs deposited on carbon surfaces, layer-by-layer growth occurred without island formation, resulting in highly uniform and coalesced IL films. The extent of morphological changes observed in the IL films was found to be influenced by two crucial factors: the thickness of the carbon film on the substrate surface and the amount of IL deposition.

Abstract The thermodynamic properties of ionic liquids (ILs) bearing alkylsilane and alkylsiloxane chains, as well as their carbon-based analogs, were investigated. Effects such as the replacement of carbon atoms by silicon atoms, the introduction of a siloxane linkage, and the length of the alkylsilane chain were explored. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to study the thermal and phase behavior (glass transition temperature, melting point, enthalpy and entropy of fusion, and thermal stability). Heat capacity was obtained by high-precision drop calorimetry and differential scanning microcalorimetry. The volatility and cohesive energy of these ILs were investigated via the Knudsen effusion method coupled with a quartz crystal microbalance (KEQCM). Gas phase energetics and structure were also studied to obtain the gas phase heat capacity as well as the energy profile associated with the rotation of the IL side chain. The computational study suggested the existence of an intramolecular interaction in the alkylsiloxane-based IL. The obtained glass transition temperatures seem to follow the trend of chain flexibility. An increase of the alkylsilane chain leads to a seemingly linear increase in molar heat capacity. A regular increment of 30 JK-1mol(-1) in the molar heat capacity was found for the replacement of carbon by silicon in the IL alkyl chain. The alkylsilane series was revealed to be slightly more volatile than its carbon-based analogs. A further increase in volatility was found for the alkylsiloxane-based IL, which is likely related to the decrease of the cohesive energy due to the existence of an intramolecular interaction between the siloxane linkage and the imidazolium headgroup. The use of Si in the IL structure is a suitable way to significantly reduce the IL's viscosity while preserving its large liquid range (low melting point and high thermal stability) and low volatilities.

Abstract This work presents a comprehensive study exploring the thermodynamics of the solid phase of a series of phenylimidazoles, encompassing experimental measurements of heat capacity, volatility, and thermal behavior. The influence of successive phenyl group insertions on the imidazole ring on thermodynamic properties and supramolecular behavior was thoroughly examined through the evaluation of 2-phenylimidazole (2-PhI), 4-phenylimidazole (4-PhI), 4,5-diphenylimidazole (4,5-DPhI), and 2,4,5-triphenylimidazole (2,4,5-TPhI). Structural correlations between molecular structure and thermodynamic properties were established. Furthermore, the investigation employed UV-vis spectroscopy and quantum chemical calculations. Additive effects arising from the introduction of phenyl groups were found through the analysis of the solid-liquid and solid-gas equilibria, as well as heat capacities. A good correlation emerged between the thermodynamic properties of sublimation and the molar volume of the unit cell, evident across 2-PhI, 4,5-DPhI, and 2,4,5-TPhI. In contrast to its isomer 2-PhI, 4-PhI exhibited greater cohesive energy due to the stronger N-HN intermolecular interactions, leading to the disruption of coplanar geometry in the 4-PhI molecules. The observed higher entropies of phase transition (fusion and sublimation) are consistent with the higher structural order observed in the crystalline lattice of 4-PhI.

Abstract This work studies the formation of deep eutectic solvents formed by one active pharmaceutical ingredient (quinine, pyrimethamine, or 2-phenylimidazopyridine) and a second component potentially acting as an excipient (betaine, choline chloride, tetramethylammonium chloride, thymol, menthol, gallic acid, vanillin, acetovanillone, 4-hydroxybenzaldehyde, syringaldehyde, propyl gallate, propylparaben, or butylated hydroxyanisole), aiming to address challenges regarding drug solubility, bioavailability, and permeability. A preliminary screening was carried out using the thermodynamic model COSMO-RS, narrowing down the search to three promising excipients (thymol, propyl gallate, and butylated hydroxyanisole). Nine solid-liquid equilibrium (SLE) phase diagrams were experimentally measured combining the three model drugs with the screened excipients, and using a combination of a visual melting method and differential scanning calorimetry. Negative deviations from thermodynamic ideality were observed in all nine systems. Furthermore, a total of four new cocrystals were found, with powder and single crystal X-ray diffraction techniques being employed to verify their unique diffraction patterns. In the thermodynamic modelling of the SLE diagrams, two COSMO-RS parametrizations (TZVP and TZVPD-FINE) were also applied, though neither consistently delivered a better description over the other.

Abstract A systematic synthetic study was performed to explain the usual trend in selectivity towards multi-coupling, over mono-coupling, in Suzuki-Miyaura reactions. This preference was observed under different reaction conditions: for various halobenzenes, using substituents on the boronic acid, and changing the catalyst and temperature. Moreover, this reaction selectivity was found to increase for more reactive systems towards oxidative addition and more diluted media. The results constitute experimental evidence that the formation of the totally substituted coupling product is kinetically favoured by a reaction path location-the proximity between the regenerated catalyst and the newly formed coupling intermediate promotes the subsequent reaction.

Abstract Microdroplets and thin films of imidazolium-based ionic liquids (ILs) of different sizes and shapes were used as confining agents for the formation of high-quality perylene crystals by vapor deposition. The role of ILs to control the nucleation and subsequent crystal growth of perylene was investigated by sequential and simultaneous depositions of both materials using indium tin oxide (ITO) as the underlying substrate. The deposition of ILs onto the perylene film surface led to the formation of a complete 2D wetting layer, followed by island growth. Higher adhesion and affinity were found for longer-chain ILs. Inverting the deposition order, the perylene microcrystals were found to grow via the ILs droplets. Additionally, the nucleation and growth of perylene monocrystals enhanced the coalescence mechanisms of the ILs droplets. This wetting process was especially evident for longer-chain ILs. The deposition of perylene onto ITO surfaces fully covered with coalesced ionic liquid films led to the formation of a perylene film with the highest homogeneity as the result of a decrease in surface mobility. The co-deposition of perylene and ILs emphasized the potential application of ILs as crystallization solvents for the formation of thin organic films with improved crystalline quality without compromising the optoelectronic properties.

Abstract The wetting behavior of ionic liquids (ILs) on the mesoscopic scale considerably impacts a wide range of scientific fields and technologies. Particularly under vacuum conditions, these materials exhibit unique characteristics. This work explores the effect of the deposition rate and substrate temperature on the nucleation, droplet formation, and droplet spreading of ILs films obtained by thermal evaporation. Four ILs were studied, encompassing an alkylimidazolium cation (C(n)C(1)im) and either bis(trifluoromethylsulfonyl)imide (NTf2) or the triflate (OTf) as the anion. Each IL sample was simultaneously deposited on surfaces of indium tin oxide (ITO) and silver (Ag). The mass flow rate was reproducibly controlled using a Knudsen cell as an evaporation source, and the film morphology (micro- and nanodroplets) was evaluated by scanning electron microscopy (SEM). The wettability of the substrates by the ILs was notably affected by changes in mass flow rate and substrate temperature. Specifically, the results indicated that an increase in the deposition rate and/or substrate temperature intensified the droplet coalescence of [C(2)C(1)im][NTf2] and [C(2)C(1)im][OTf] on ITO surfaces. Conversely, a smaller impact was observed on the Ag surface due to the strong adhesion between the ILs and the metallic film. Furthermore, modifying the deposition parameters resulted in a noticeable differentiation in the droplet morphology obtained for [C(8)C(1)im][NTf2] and [C(8)C(1)im][OTf]. Nevertheless, droplets from long-chain ILs deposited on ITO surfaces showed intensified coalescence, regardless of the deposition rate or substrate temperature.

Abstract This work reports the formation of silver nanoparticles (AgNPs) by sputter deposition in thin films of three different ionic liquids (ILs) with the same anion (bis(trifluoromethylsulfonyl)imide) and cation (imidazolium), but with different alkyl chain lengths and symmetries in the cationic moiety ([C(4)C(1)im][NTf2], [C(2)C(2)im][NTf2], and [C(5)C(5)im][NTf2]). Ionic liquid (IL) films in the form of microdroplets with different thicknesses (200 to 800 monolayers) were obtained through vacuum thermal evaporation onto glass substrates coated with indium tin oxide (ITO). The sputtering process of the Ag onto the ILs when conducted simultaneously with argon plasma promoted the coalescence of the ILs' droplets and the formation, incorporation, and stabilization of the metallic nanoparticles in the coalesced IL films. The formation/stabilization of the AgNPs in the IL films was confirmed using high-resolution scanning electron microscopy (SEM) and UV-Vis spectroscopy. It was found that the IL films with larger thicknesses (600 and 800 monolayers) were better media for the formation of AgNPs. Among the ILs used, [C(5)C(5)im][NTf2] was found to be particularly promising for the stabilization of AgNPs. The use of larger IL droplets as capture media was found to promote a better stabilization of the AgNPs, thereby reducing their tendency to aggregate.

Abstract Diels-Alder cycloaddition is a common synthetic approach to functionalize fullerenes. However, the stability of such fullerene adducts is hampered by the existence of the Retro Diels-Alder (RDA) reaction. Herein, the RDA reactions in the solid phase of the mono and bisadducts of C60 with indene, IC60MA and IC60BA, were studied by differential scanning calorimetry and thermogravimetric analysis. The RDA reaction in solid IC60MA occurs at a higher temperature than in IC60BA. IC60MA decomposition follows a first-order rate law and in IC60BA it is described by two consecutive first-order reaction steps. The decomposition of both adducts yields a metastable C60 solid. The higher decomposition temperature of IC60MA is due to higher activation energy, Ea, and lower preexponential factor, A. The values of Ea for the RDA reactions differ due to crystal packing efficiency in the solids. The measured A values were found to reflect the statistical weight of C60-Indene bonds that can be broken. A reaction mechanism was proposed for the decomposition of the fullerene adducts. The enthalpies of sublimation of IC60MA and IC60BA were estimated based on the enthalpies of their respective RDA reactions. Additionally, the heat capacities of the solid fullerenes (C60, IC60MA, and IC60BA), at T = 298.15 K, were measured by highprecision heat capacity drop calorimetry, indicating that the rotational motion of C60 in the crystal increases its expected heat capacity.