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.