Modular Cavities: Induced Fit of Polar and Apolar Guests into Halogen-Based Receptors

Neutral triangular macrocyclic compounds, [PdX₂(4,7-phen)]₃·(DMF)₃·Et₂O (X = Cl, Br; 4,7-phen = 4,7-phenanthroline; DMF = N, N'-dimethylformamide; Et₂O = diethyl ether), were synthesized, and their molecular structures were characterized. Solution-state ¹H NMR results suggested the formation of metal-ligand bonds, and single-crystal X-ray crystallography revealed clear triangular structures. A detailed examination of the structures indicated the formation of two kinds of cavities in the solid state, where a triangular unit works as a halogen-based receptor for polar and apolar solvents through weak hydrogen-bonding and dipole-dipole interaction.