A Tetrameric Cobalt(II) Assembly Integrating Aggregation-Induced Emission and Weak Antiferromagnetic Coupling

A supramolecularly rigidified tetrameric cobalt(II) assembly, [<b>Co</b>_<b>4</b><b>T</b>_<b>8</b><b>(H</b>_<b>2</b><b>O)</b>_<b>2</b>] (<b>T-Co</b>), where <b>T = Tropolonate ion</b>, has been constructed using tropolonate ligands to investigate the interplay between aggregation-controlled photophysics and magnetic exchange interactions in multinuclear 3d systems. Single-crystal analysis reveals a distorted octahedral Co₄ framework interconnected through oxygen-bridged pathways and reinforced by cooperative O–H···O hydrogen bonding, π–π stacking, and C–H···π interactions, producing an extended caterpillar-like supramolecular arrangement.

The restricted structural dynamics imposed by this densely packed architecture give rise to pronounced aggregation-induced emission (AIE) behavior, in which progressive aggregation in water-rich media enhances fluorescence by suppressing nonradiative relaxation channels. Dynamic light scattering measurements correlate the emissive enhancement with aggregate growth, confirming aggregation-governed excited-state modulation.