Luís M. N. B. F. Santos

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.