Molecular simulation of folding and aggregation of multi-core polycyclic aromatic compounds

Abstract

Compared with polycyclic aromatic compounds (PACs) that have a single polyaromatic core, those having multiple cores connected by aliphatic chains can undergo significant internal conformational change, leading to folding, the stacking between the cores within the same molecule. In this work, we investigated this interesting phenomenon using molecular dynamics simulations, performed in three different solvents: water, heptane and toluene. In addition, by having several multi-core PACs in the same solution, the relationship between intramolecular folding and intermolecular aggregation was elucidated. In water, a single multi-core PAC preferred to stay in the unfolded state; contrarily, folded configuration became dominant when multiple molecules aggregated. In heptane and toluene, a multi-core PAC molecule could switch easily between folded and unfolded configurations, regardless of whether it was in single dispersed or aggregated states. Introduction of single-core PACs further modified the folding characteristics of multi-core PACs in water and heptane. This work provided fundamental insights into the interplay between folding, homoaggregation (between multi-core PACs) and heteroaggregation (between multi-core and single-core PACs) in a colloidal system.