UNRAVELING THE SOLVATOCHROMISM OF A TRIARYLMETHANE DYE BY RESONANCE RAMAN SPECTROSCOPY

The effect of the solvent on the electronic properties of the triarylmethane dye rosolic acid (RA) is investigated by means of UV-VIS and resonance Raman (RR) spectroscopies. The comparison of the solvatochromic behavior of both neutral and dianionic species of RA in acetonitrile, dimethylsulfoxide, and methanol illustrates the effect of polarity and hydrogen bonding on their electronic transitions. The resonance Raman analysis revealed two distinct chromophores in both neutral and dianionic species: i) one located at the central carbon atom, acting as an electron acceptor, and ii) the other involving the π-system of the donor groups. The observed resonance Raman excitation profiles are solvent dependent and could be interpreted as the effect of the solvent on the planarity of the aromatic rings in relation to the central carbon atom. In the case of neutral RA species, having C2 symmetry, specific hydrogen bonding interactions are responsible for inducing a symmetry increase. The opposite effect was observed for the dianionic species [RA]2-, having D3 propeller symmetry, where the interactions with the solvent induces a lowering of the symmetry.</div

Design of Ionic Liquids for Fluorinated Gas Absorption: COSMO-RS Selection and Solubility Experiments

In recent years, the fight against climate change and the mitigation of the impact of fluorinated gases (F-gases) on the atmosphere is a global concern. Development of technologies that help to efficiently separate and recycle hydrofluorocarbons (HFCs) at the end of the refrigeration and air conditioning equipment life is a priority. The technological development is important to stimulate the F-gas capture, specifically difluoromethane (R-32) and 1,1,1,2-tetrafluoroethane (R-134a), due to their high global warming potential. In this work, the COSMO-RS method is used to analyze the solute–solvent interactions and to determine Henry’s constants of R-32 and R-134a in more than 600 ionic liquids. The three most performant ionic liquids were selected on the basis of COSMO-RS calculations, and F-gas absorption equilibrium isotherms were measured using gravimetric and volumetric methods. Experimental results are in good agreement with COSMO-RS predictions, with the ionic liquid tributyl­(ethyl)­phosphonium diethyl phosphate, [P2444]­[C2C2PO4], being the salt presenting the highest absorption capacities in molar and mass units compared to salts previously tested. The other two ionic liquids selected, trihexyltetradecylphosphonium glycinate, [P66614]­[C2NO2], and trihexyl­(tetradecyl)­phosphonium 2-cyano-pyrrole, [P66614]­[CNPyr], may be competitive as far as their absorption capacities are concerned. Future works will be guided on evaluating the performance of these ionic liquids at an industrial scale by means of process simulations, in order to elucidate the role in process efficiency of other relevant absorbent properties such as viscosity, molar weight, or specific heat

Design of Ionic Liquids for Fluorinated Gas Absorption: COSMO-RS Selection and Solubility Experiments

In recent years, the fight against climate change and the mitigation of the impact of fluorinated gases (F-gases) on the atmosphere is a global concern. Development of technologies that help to efficiently separate and recycle hydrofluorocarbons (HFCs) at the end of the refrigeration and air conditioning equipment life is a priority. The technological development is important to stimulate the F-gas capture, specifically difluoromethane (R-32) and 1,1,1,2-tetrafluoroethane (R-134a), due to their high global warming potential. In this work, the COSMO-RS method is used to analyze the solute–solvent interactions and to determine Henry’s constants of R-32 and R-134a in more than 600 ionic liquids. The three most performant ionic liquids were selected on the basis of COSMO-RS calculations, and F-gas absorption equilibrium isotherms were measured using gravimetric and volumetric methods. Experimental results are in good agreement with COSMO-RS predictions, with the ionic liquid tributyl­(ethyl)­phosphonium diethyl phosphate, [P2444]­[C2C2PO4], being the salt presenting the highest absorption capacities in molar and mass units compared to salts previously tested. The other two ionic liquids selected, trihexyltetradecylphosphonium glycinate, [P66614]­[C2NO2], and trihexyl­(tetradecyl)­phosphonium 2-cyano-pyrrole, [P66614]­[CNPyr], may be competitive as far as their absorption capacities are concerned. Future works will be guided on evaluating the performance of these ionic liquids at an industrial scale by means of process simulations, in order to elucidate the role in process efficiency of other relevant absorbent properties such as viscosity, molar weight, or specific heat