Enhanced Solid-State Luminescence of Supramolecular Tessellation Assemblies Through Förster Resonance Energy Transfer From Counterions.

The development of straightforward strategies for constructing supramolecular tessellations with enhanced solid-state luminescence has attracted growing interest in supramolecular chemistry and luminescent materials. Herein, we report the formation of diverse supramolecular tiling patterns by combining electron-deficient bipyridinium-based cationic macrocycles with either naphthalene-1-sulfonate or naphthalene-2-sulfonate counterions directly. Single-crystal X-ray diffraction reveals distinct tessellated superstructures assembled from 3,3'-bipyridinium macrocycles, stabilized by a network of electrostatic interactions, hydrogen bonding, π···π stacking, and CH···π interactions. These assemblies exhibit red-shifted and enhanced solid-state fluorescence, attributed to Förster resonance energy transfer (FRET) between the macrocycles and their aromatic counterions. Crystallographic and computational studies provide molecular-level insights into the noncovalent forces governing both the assembly process and luminescence enhancement. This work establishes a facile design strategy for constructing luminescent supramolecular tessellations and offers a deeper understanding of their structure-property relationships.