Solvent Thermodynamic Driving Force Controls Stacking Interactions between Polyaromatics

Polyaromatic dye molecules employed in photovoltaic and electronic applications are often processed in organic solvents. The aggregation of these dyes is key to their applications, but a fundamental molecular understanding of how the solvent environment controls the stacking of polyaromatics is unclear. This study reports initial results from Monte Carlo simulations of how various acene molecule dimers stack when they are dissolved in different solvents. Free energies computed using full dispersion interactions versus those with sterics only suggest that solvent entropy alone accounts for the majority of the stacking free energy in solvents with compact molecular geometries such as carbon tetrachloride. However, in contrast with carbon tetrachloride, we also observe significant variations in the stacking free energies of naphthalene, anthracene, and tetracene across other solvents such as toluene and cyclohexane. The weak attractive dispersion interactions between the acene solutes and planar and near-pla...