Filipa Siopa

Sustainable design for environment-friendly mono and dicationic cholinium-based ionic liquids.

Cholinium-based ionic liquids are receiving crescent interest in diverse areas of application given their biological compatibility and potential for industrial application. In this work, mono and dicationic cholinium ionic liquids as well as cholinium derivatives were synthesized and their toxicity assessed using the luminescent bacteria Vibrio fischeri. A range of cholinium derivatives was synthesized, using different amines and the correspondent brominated derivatives, through the alkylation of the amine with the halide in MeCN. The results indicate that their toxicity is highly dependent on the structural modifications of the cholinium cation, mainly related to the alkyl side or linkage chain length, number of hydroxyethyl groups and insertion of carbon-carbon multiple bonds. The data indicated that it is possible to perform environmentally advantageous structural alterations, namely the addition of double bonds, which would not negatively affect V. fischeri. Moreover, the dicationic compounds revealed a significantly lower toxicity than the monocationic counterparts. The picture emerging from the results supports the idea that cholinium derivatives are promising ionic liquids with a low environmental impact, emphasizing the importance of a careful and directed design of ionic liquid structures.

Toxicological evaluation of magnetic ionic liquids in human cell lines

Magnetic ionic liquids (MILs) are new solvents with an interesting broad of applications however their toxicity is still an open issue. In this paper we report the toxicity of [C(8)MIM] and [Choline-C(n)] based magnetic ionic liquids assessed in two human cell lines: normal skin fibroblasts (CRL-1502) and colorectal adenocarcinoma cells (CaCo-2), acquiring this last characteristics of human enterocytes after differentiation. The results showed that [CoCl(4)] and [MnCl(4)] are more prone to generate cytotoxicity.

Plasma membrane permeabilisation by ionic liquids: a matter of charge

Understanding the mechanisms of toxicity of ionic liquids at the molecular level is crucial for their conscious design as to promote higher acceptability as green solvents in a wide range of applications. In this systematic study, we investigated the effects of three families of ionic liquids on the plasma membrane of the filamentous fungus Aspergillus nidulans. Using fluorescence microscopy and gene expression analysis, we were able to demonstrate that the widely studied 1-alkyl-3-methylimidazolium chlorides with long alkyl substituents cause membrane permeabilisation. In opposition, the biocompatibility of cholinium alkanoates was reinforced here, even though their toxicity also increases with the elongation of the anion. Further investigating the effects of charge on membrane permeabilisation, we observed that a series of alkyl-(2-hydroxyethyl)-dimethylammonium bromides led to permeabilisation of the fungal plasma membrane by increasing the length of one alkyl substituent in the cholinium cation. We hypothesise that the chemical nature of the plasma membrane, which presents a heterogeneous charge distribution along its surface, is pivotal for the membrane permeabilising effects of ionic liquids. This study may inspire a new trend in the ionic liquid field: to give preference for the development of compounds carrying functionalised anions as greener alternatives to those carrying functionalized cations.

New low viscous cholinium-based magnetic ionic liquids

Magnetic ionic liquids (MILs) are a type of ionic liquids (ILs) that have paramagnetic metal based anions, and thus they can respond to an external magnetic field. Owing to the high propensity of these anions to crystallize, there are only few reported MILs that are liquid at room temperature. This study describes a new family of cholinium based ILs containing two and three ethanol side chains, that are liquid at room temperature, even in combination with paramagnetic anions. In addition, these new family of ILs are prone to the generation of low toxicities on human cell lines.

A 1,3,5-triazine based polymer as a nonlinear near-infrared antenna for two-photon activated volumetric optical memory devices

The ability of a 1,3,5-triazine based polymer to work as a nonlinear near-infrared (NIR) antenna in functional optical materials is discussed. The push–pull polymer is composed of alternating electron acceptor cores of 2,4,6-tris(thiophen-2-yl)-1,3,5-triazine, bridged by electron donor groups of 9,9-dihexyl-9H-fluorene. It has been tailored for high two-photon absorption and efficient up-conversion of the excitation energy into fluorescence emission. These properties are here explored in the operation of prototypical storage material for volumetric nonlinear optical memory devices. Multilayer data storage is demonstrated in composite films of photochromic (PC) molecules doped with the polymer. The two-photon excitation of the polymer triggers a unidirectional isomerization of the PC molecules (a cycloreversion process from the closed to the open isomer) via Forster resonant energy transfer. Data recording with as little as 1 ms of exposure time and 1 mW of 740 nm radiation is accomplished.

Ecotoxicological evaluation of magnetic ionic liquids

Although magnetic ionic liquids (MILs) are not yet industrially applied, their continued development and eventual commercial use may lead to their appearance into the aquatic ecosystem through accidental spills or effluents, consequently promoting aquatic contaminations. Furthermore, the deficient information and uncertainty surrounding the environmental impact of MILs could be a major barrier to their widespread industrial application and international registration. Thus, in the present work, a range of cholinium salt derivatives with magnetic properties was synthesized and their ecotoxicity was evaluated towards the luminescent bacteria Vibrio fischeri. The results suggest that all MILs structures tested are moderately toxic, or even toxic, to the bacteria. Furthermore, their toxicity is highly dependent on the structural modifications of the cation, namely the alkyl side chain length and the number of hydroxyethyl groups, as well as the atomic number of the metal anion. Finally, from the magnetic anions evaluated, the [MnCl4]2- is the less toxic. In order to improve the knowledge for the prospective design of environmentally safer MILs, it is important to expand this study to other aquatic organisms at different trophic levels.