Molecular Dynamics Simulations of the Outer-Sphere Reorganization Energies of Aqueous Oligothiophenes
Year: 2026
Type: preprint
Abstract: The outer-sphere reorganization energy (λout) contributes directly to the activation barrier for hole transfer in aqueous organic mixed ionic–electronic conductors, yet it is usually estimated from dielectric continuum models rather than computed explicitly. Here, λout is computed for doped oligothiophenes in explicit aqueous electrolyte by all-atom molecular dynamics with an electronic continuum correction, using vertical-energy-gap fluctuation estimators and thermodynamic integration. Increasing the degree of polymerization from one to six decreases λout from 0.84 to 0.55 eV owing to hole delocalization; λout saturates beyond the trimer and remains comparable to the inner-sphere reorganization energy (0.48 eV for the hexamer). Across side-chainfunctionalized thiophene monomers, λout varies by ≈0.2 eV and scales with the square of the doping-induced change in molecular dipole moment, whereas for trimers and hexamers it converges to ≈0.53 eV irrespective of whether the side chain is neutral, cationic, or anionic. These results identify backbone delocalization as the principal determinant of λout for aqueous conjugated oligomers.
Source: ChemRxiv
Authors: Huihang Qiu, Nicholas E. Jackson
Institution: University of Illinois Urbana-Champaign
Language: English
Subfield: Physical and Theoretical Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7220726800