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.