Synthesis and Characterization of a Chromo-Extractant to the Probe Liquid–Liquid Interface in a Solvent Extraction Process

Second harmonic generation experiments for probing liquid–liquid interfaces and more specifically the ion transfer through buried interfaces may turn out to be highly relevant. However, it requires an increase in the reflected nonlinear signal and thus an enhancement of the hyperpolarizability of the extractant molecules that boost the ion partitioning. A new amphiphilic liganda malonamide azobenzene derivativewas synthesized by combining a diamide functional group with high affinity for trivalent f-block elements and an azobenzene group within its aliphatic part. The ability of this molecule to extract and form hydrophobic complexes with rare-earth cations at the methylcyclohexane/H2O interface was first evaluated. It was also shown that the isomerization of the azobenzene group under UV irradiation induces a slight change in the surface tension between the two liquid phases. As desired, this new extractant molecule has a strong nonlinear response and can be detected at the water/oil interface.