Quantum topological modeling of asphaltene stabilization: unraveling steric shielding effects.

CONTEXT: This computational study investigates the molecular-level interaction between asphaltene (AO) nanoaggregates and the amphiphilic 1-(octylamino)propan-2-ol (OAP) inhibitor using density functional theory (DFT) calculations and complementary experimental analysis. Quantum theory of atoms in molecules (QTAIM) analysis indicates that OAP interacts with the AO surface through non-covalent interactions, with binding energies reaching - 24.67 kJ/mol and |VB|/GB ratios below unity. Electron localization function (ELF), localized orbital locator (LOL), non-covalent interaction (NCI), and highest occupied molecular orbital/lowest unoccupied molecular orbital (HOMO-LUMO) analyses suggest charge redistribution and electronic complementarity within the OAP-AO complex, supporting the proposed steric shielding mechanism. Complementary dynamic light scattering (DLS) measurements showed a reduction in the median aggregate size from 42.4 to 17.7 nm following OAP addition, which may indicate improved aggregate dispersion and enhanced colloidal stability. Collectively, the computational and experimental findings provide molecular-level insight into the proposed stabilization mechanism of the OAP-AO system and contribute to a better understanding of asphaltene inhibitor-aggregate interactions. METHODS: A comprehensive quantum-topological framework encompassing DFT, QTAIM, ELF, and LOL was employed. Geometry optimizations and electronic structure calculations were performed in the gas phase using the Gaussian 09 package with the B3LYP hybrid functional, Grimme's D3(BJ) dispersion correction, and the 6-311G(d,p) basis set. Topological descriptors at bond critical points were computed using Multiwfn 3.8. HOMO/LUMO isosurfaces and molecular electrostatic potential (MEP) maps were generated using GaussView 06, optimized structures were visualized with VESTA 3.5.5, and three-dimensional NCI plots were rendered using the VMD software package. Complementary DLS measurements were performed at 298 K using a HORIBA LB-550 analyzer to provide experimental support for the computational analysis.