Self-Assembly of [M₈L₄] and [M₄L₂] Fluorescent Metallomacrocycles with Carbazole-Based Dipyrazole Ligands

Fluorescent carbazole-based dipyrazole ligands (H2L1–4) were employed to coordinate with dipalladium corners ([(phen)2Pd2(NO3)2]­(NO3)2, [(dmbpy)2Pd2(NO3)2]­(NO3)2, or [(15-crown-5-phen)2Pd2(NO3)2]­(NO3)2, where phen = 1,10-phenanthroline and dmbpy = 4,4′-dimethyl-2,2′-bipyridine, in aqueous solution to afford a series of positively charged [M8L4]8+ or [M4L2]4+ multimetallomacrocycles with remarkable water solubility. Their structures were characterized by 1H NMR spectroscopy, electrospray ionization mass spectrometry, and elemental analysis and in the cases of 1·8BF4– ([(phen)8Pd8L14]­(BF4)8), and 3·4BF4– ([(phen)4Pd4L22]­(BF4)4) by single-crystal X-ray diffraction analysis. Complexes 3–8 are square-type hybrid metallomacrocycles, while complexes 1 and 2 exhibit folding cyclic structures. Interestingly, in single-crystal structures of 1·8BF4– and 3·4BF4–, BF4– anions are trapped in the dipalladium clips through anion−π interaction. The luminescence properties and interaction toward anions of these metallomacrocycles were discussed.