Parallel-stacked aromatic hosts for orienting small molecules in a magnetic field: Induced residual dipolar coupling by encapsulation

"Chemical equation presented" 3D structural information can be obtained from the residual dipolar coupling (RDC) from biomolecules trapped within alignment media (e.g., liquid crystals). Unfortunately, RDC is not a suitable method for small molecules, as the intermolecular interactions with common alignment media are weak and ineffective. We report that columnar molecular hosts with parallel-aligned aromatics are magnetically oriented and exhibit observable RDC. And, upon encapsulation, an RDC silent guest (pyrene) is placed in alignment with the host and magnetic field and displays detectable induced RDC. Thus, the discrete hosts with aligned aromatic panels behave as molecular alignment media or "magnetic aligners" for small molecules. This method will be further applied to the 3D structure determination of more complex guest molecules.