Self-Assembly and Host−Guest Interaction of Metallomacrocycles Using Fluorescent Dipyrazole Linker with Dimetallic Clips

By employing diimine ligands coordinated dimetallic clips ([(bpy)2Pd2(NO3)2](NO3)2 or [(phen)2Pd2(NO3)2](NO3)2, where bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline) as the corner and anthracene-, naphthalene-, and benzene-based dipyrazolate dianions as the linker, a series of positively charged metallomacrocycles ([M4L2]4+ or [M8L4]8+) have been synthesized through a directed self-assembly method in aqueous solution. Every macrocycle has a cavity to bind solvent molecules or anions. The structures were characterized by elemental analysis, 1H and 13C NMR, electrospray ionization mass spectrometry, and single crystal X-ray diffraction analysis for compound 1·4PF6¯ (1 = {[(bpy)Pd]4L12}4+), 3·4PF6¯·8CH3CN·H2O (3 = {[(bpy)Pd]4L22}4+), and 7·4PF6¯·6H2O (7 = {[(bpy)Pd]4L52}4+). The 1:1 host−guest complexation for anthracene-based dipyrazolate-bridged macrocycles with aromatic guests was investigated via UV−vis and fluorescent titration.