Nonplanar Ladder-Type Polycyclic Conjugated Molecules: Structures and Solid-State Properties

Using an efficient intramolecular carbon–carbon cross-coupling reaction, a series of new ladder-type conjugated molecules have been prepared successfully in high yields. Such a pyran-fused polycylic structure possesses an extended π-conjugated backbone with flexible conformation, which gives these molecules interesting properties, including high solubility in common organic solvents, excellent thin film-forming abilities, blue fluorescent emission with good quantum yields, and aggregate formation in a binary solvent. The self-assembly behaviors of these molecules as well as various nanostructures can be finely tailored by varying the substituted group on the molecular periphery. The powder and single-crystal X-ray diffraction analyses revealed that the synergetic effect of π–π stacking and van der Waals interactions play a key role in controlling the morphologies of these aggregates. More importantly, self-assembled molecules exhibit good fluorescent performance, due to their twist backbone conformation.