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)(2)Pd-2(NO3)(2)](NO3)(2), [(dmbpy)(2)Pd-2(NO3)(2)](NO3)(2), or [(15-crown-5-phen)(2)Pd-2(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 H-1 NMR spectroscopy, electrospray ionization mass spectrometry, and elemental analysis and in the cases of 1.8BF(4)(-) ([(phen)(8)Pd8L41](BF4)(8)), and 3.4BF(4)(-) ([(phen)(4)Pd4L22](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 1.8BF(4)(-) and 3.4BF(4)(-), BF4- anions are trapped in the dipalladium clips through anion-pi interaction. The luminescence properties and interaction toward anions of these metallomacrocycles were discussed.