O Efeito da Água Sobre as Propriedades Químicas dos Íons Ag+ e Cu2+ em Solventes Eutéticos Baseados em Cloreto de Colina

Abstract

The eutectic solvents are obtained from the mixture of two components whose melting points are greater than the melting point of the resultant mixture. This solvent has gained prominence compared with the ionic liquids because they are biodegradable, cheap, good ionic conductivity and they are electrochemically stable in wide potential range. The eutectic solvents are employed in different fields such as organic synthesis, electrodeposition of metals, drugs delivery, catalysis among others. An important propriety of the eutectic solvent its hygroscopicity, that is, they are solvents capable of absorbing moisture from the air. Consequently, some proprieties are altered. Therefore, it is interesting to understand the impact of the presence of water in eutectic solvents. In the present study were performed experimental and theoretical procedure using molecular dynamic simulations in systems constituted by solutions of Ag+ ions in reline (eutectic solvent with molar ratio 1:2 of choline chloride and urea, respectively) and Cu2+ ions in reline and ethaline (eutectic solvent with molar ratio 1:2 of choline chloride and ethylene glycol, respectively). These solutions undergo gradual addition of water varying the percentages v/v of 0.1; 0.5; 1.0; 5.0 and 10.0 %. The experimental measures showed a shift of the reduction potential for both ions due to the water addition. The analysis of the results obtained from molecular dynamic simulations showed which occurs the exchange of ethylene glycol and urea molecules by water molecules in the coordination of Ag+ and Cu2+ ions. Silver ions presented an organization of their ligands near the tetrahedron, while the ions copper, a layer close to the octahedral. In addition, it has been observed that the water molecules take up “free spaces” in the eutectic solvent.