Aqueous solubilization of hydrophobic compounds by inorganic nano-ions: An unconventional mechanism

Hypothesis: Solubilization of hydrophobic compounds in water is commonly performed by using organic solubilizers such as hydrotropes, surfactants, co-solvents, and macrocycles to form host-guest com-plexes. 3,30-commo-bis[closo-1,2-dicarba-3-cobaltadodecaborane] derivatives (COSANs) are fully inor-ganic and non-amphiphilic ionic boron clusters with nanometric size (nano-ions) showing superchaotropic properties as they strongly bind to neutral organic molecules. Therefore, we expect COSANs to act as solubilizers of sparingly water-soluble molecules, but with a mechanism different from all other organic solubilizers known so far. Experiments: The aqueous solubilization efficiency of COSANs towards butanol was evaluated by deter-mining phase diagrams and comparing them to classical solubilizers. Nanostructuration of the mixture was studied using UV spectroscopy, small-angle X-ray, and neutron scattering with contrast variation.Findings: COSANs act as efficient aqueous solubilizers of medium-chain alcohols (0.6 < log P < 1.5). Unlike surfactants, COSAN is an efficient solubilizer in its monomeric state, at concentrations well below its crit-ical aggregation concentration. Solubilization by COSAN takes place with a bi-dimensional anisotropic growth of COSAN/butanol co-assemblies, whereas solubilization by surfactant occurs via an isotropic swelling of micelles. Appealingly, COSANs/2-butanol co-assemblies efficiently solubilize more hydropho-bic compounds with log P values up to around 6, offering new opportunities in many applied fields.(c) 2023 Elsevier Inc. All rights reserved.

Automated summary

The study found that COSANs act as efficient aqueous solubilizers of medium-chain alcohols in their monomeric state. Unlike surfactants, COSANs dissolve through a bi-dimensional anisotropic growth of COSAN/butanol co-assemblies. Additionally, COSANs/2-butanol co-assemblies can efficiently solubilize more hydrophobic compounds, offering new opportunities in many applied fields.