[M8L4]8+-Type Squares Self-Assembled by Dipalladium Corners and Bridging Aromatic Dipyrazole Ligands for Iodine Capture

Square-like metallamacrocyclic palladium(II) complexes [M8L4]8+ (1-7) were synthesized by reacting aromatic dipyrazole ligands (H2L1-H2L3 with pyromellitic arylimide-, 1,4,5,8-naphthalenetetracarboxylic arylimide-, and anthracene-based aromatic groups, respectively) with dipalladium corners ([(bpy)2Pd2(NO3)2](NO3)2, [(dmbpy)2Pd2(NO3)2](NO3)2, or [(phen)2Pd2(NO3)2](NO3)2, where bpy = 2,2'-bipyridine, dmbpy = 4,4'-dimethyl-2,2'-bipyridine, and phen = 1,10-phenanthroline) in aqueous solutions via metal-directed self-assembly. Metallamacrocycles 1-7 were fully characterized by 1H and 13C nuclear magnetic resonance spectroscopy and electrospray ionization mass spectrometry, and the square structure of 7·8NO3- was further confirmed via single crystal X-ray diffraction. These square-like metallamacrocycles exhibit effective performance for iodine adsorption.