Self-assembly of [M8L4] and [M4L2] fluorescent metallomacrocycles with carbazole-based dipyrazole ligands

Fluorescent carbazole-based dipyrazole ligands (H(2)L(1-4)) were employed to coordinate with dipalladium corners ([(phen)(2)Pd(2)(NO(3))(2)](NO(3))(2), [(dmbpy)(2)Pd(2)(NO(3))(2)](NO(3))(2), or [(15-crown-5-phen)(2)Pd(2)(NO(3))(2)](NO(3))(2), where phen = 1,10-phenanthroline and dmbpy = 4,4'-dimethyl-2,2'-bipyridine, in aqueous solution to afford a series of positively charged [M(8)L(4)](8+) or [M(4)L(2)](4+) multimetallomacrocycles with remarkable water solubility. Their structures were characterized by (1)H NMR spectroscopy, electrospray ionization mass spectrometry, and elemental analysis and in the cases of 1·8BF(4)(-) ([(phen)(8)Pd(8)L(1)(4)](BF(4))(8)), and 3·4BF(4)(-) ([(phen)(4)Pd(4)L(2)(2)](BF(4))(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)(-), BF(4)(-) anions are trapped in the dipalladium clips through anion-π interaction. The luminescence properties and interaction toward anions of these metallomacrocycles were discussed.