Controlling Conformations of Conjugated Polymers and Small Molecules: The Role of Nonbonding Interactions

The chemical variety present in the organic electronics literature has motivated us to investigate potential nonbonding interactions often incorporated into conformational "locking" schemes. We examine a variety of potential interactions, including oxygen-sulfur, nitrogen-sulfur, and fluorine-sulfur, using accurate quantum-chemical wave function methods and noncovalent interaction (NCI) analysis on a selection of high-performing conjugated polymers and small molecules found in the literature. In addition, we evaluate a set of nonbonding interactions occurring between various heterocyclic and pendant atoms taken from a group of representative pi-conjugated molecules. Together with our survey and set of interactions, it is determined that while many nonbonding interactions possess weak binding capabilities, nontraditional hydrogen-bonding interactions, oxygen-hydrogen (CH center dot center dot center dot O) and nitrogen-hydrogen (CH center dot center dot center dot N), are alone in inducing conformational control and enhanced planarity along a polymer or small molecule backbone at room temperature.