Elucidating the Hydrotropic Mechanism of the Antagonistic Salt PPh 4 Cl.

PPh 4 Cl is an antagonistic salt that recently showed promise as a hydrotropic agent. Here, we give mechanistic insights into the PPh 4 Cl-assisted solubility of a dye molecule using molecular dynamics simulations. Our findings reveal that dye molecules aggregate into a cluster which leads to an accumulation of PPh 4 + ions in its vicinity and subsequent exclusion of water molecules from the region. The structural organization is attributed to the preferential interaction of dye molecules and PPh 4 Cl. The origin of such preference arises from the difference in π-π and CH -π interaction among the pairs. The hydrodynamic radius of PPh 4 Cl indicates a low propensity for cluster formation, which enhances its hydrotropic behavior. The process of dye dissolution is thermodynamically favored and occurs through a cooperative mechanism. Our studies provide molecular insight into experimental observations crucial for the design of novel hydrotropes with enhanced solubilizing properties.