Se-annulated unsymmetrical perylene ester imide exhibiting room-temperature columnar hexagonal mesophases.

Incorporating heteroatoms into π-conjugated aromatic cores enables the formation of robust self-assembled architectures by leveraging enhanced intermolecular interactions, including dipole-dipole, van der Waals, and σ-hole mediated non-covalent interactions. These improved self-assemblies are key for achieving superior performance in organic semiconductors. Herein, we present the rational design and synthesis of a selenium-annulated unsymmetrical perylene diester imide (PEI-SeST), wherein a swallow-tail moiety at the imide position, in concert with decyl substituents at the ester functionalities, stabilizes an enantiotropic columnar hexagonal liquid crystalline phase at ambient temperature, which is in contrast to the perylene ester imide derivative without a heteroatom. Selenium incorporation via Cadogan cyclization enhances self-assembly through Se⋯Se van der Waals and Se⋯O σ-hole interactions, fine-tuning molecular packing and electronic properties. A comparative analysis encompassing thermotropic, photophysical, and electrochemical properties of this series-including N- and S-annulated derivatives (PEI-NST and PEI-SST), as well as the parent perylene ester imide (PEIST), revealed the profound influence of selenium incorporation on self-assembly and material properties. This work underscores the impactful role of heteroatom bay-annulation in governing self-assembly and functional properties, offering a robust molecular design platform for advanced optoelectronic materials, including organic photovoltaics and liquid crystalline semiconductors.