Reconsidering the Roles of Noncovalent Intramolecular “Locks” in π‑Conjugated Molecules

The extrinsic properties of organic semiconductors (OSC) are connected both to local and long-range thin-film morphologies. While it is desirable to synthetically regulate OSC solid-state structure, there remains limited understanding of the rich and complex relationships among the molecular structure of the chromophores that comprise the OSC and the functional parameters of the processing environment (e.g., solvent, solution composition, and temperature), each of which will impact the final OSC structure and characteristics. Here, we are interested in exploring how chromophore chemistry and the processing environment impact the structures of oligomers comprised of electron-rich donor and electron-deficient acceptor moieties, as conformational variations among these groups can impact OSC formation. Specifically, we make use of quantum-chemical calculations and molecular dynamics (MD) simulations to systematically investigate how variations in molecular design and processing chemistry influence the structure, dynamics, and aggregation tendencies of donor–acceptor (D–A) oligomers in solution. The investigation reveals preferential rotational isomer populations as a function of the oligomer chemistry, solvent environment, and oligomer concentration. Notably, questions are brought forward concerning the current emphasis on the roles of noncovalent intramolecular interactions in the design of OSC building blocks. Overall, the results provide an in-depth molecular-scale foundation to allow for thermodynamic and kinetic control of OSC morphology development through chromophore design and solvent optimization.