Halogen-Bonded Cocrystals for Tunable Phosphorescence Emission of Pt Complexes.

Noncovalent interactions, such as halogen bonding (HaB) and π-stacking, play a pivotal role in directing supramolecular assemblies and tuning photophysical properties. Herein, we report the synthesis, X-ray structural characterization, and photophysical properties of cocrystals and host:guest adducts formed by iodopentafluorobenzene (G) with three distinct Pt(II) complexes (1-3). The cocrystals exhibit a combination of short I···Pt halogen bonds and π-hole···Pt interactions in the solid state, highlighting the dual role of the Pt(II) center as a halogen bond acceptor and a π-stacking participant. Interestingly, an enhancement in emission intensity is observed for complexes 1·G and 2·G upon mixing of 1 or 2 with G in a chloroform solution, attributed to synergistic σ-hole···[dz2-PtII] interactions that reduce the flexibility of the square-planar complex and the double heavy atom effect. These results emphasize the potential of host:guest interactions as a strategy for enhancing luminescence efficiency and open new avenues for designing functional materials for sensing and optoelectronic applications.