Solution self-assembly, spontaneous deprotonation, and crystal structures of bipyrazolate-bridged metallomacrocycles with dimetal centers

A series of nanosized cavity-containing bipyrazolate-bridged metallomacrocycles with dimetal centers, namely, {[(bpy)M]₈L ₄}(NO₃)₈ [L = 3,3′,5,5′- tetramethyl-4,4′-bipyrazolyl, Pd 1, Pt 2; 1,4-bis-4′-(3′, 5′-dimethyl)-pyrazolylbenzene), Pd 5; and 1,4-bis-4′-(3′, 5′-dimethyl)-pyrazolylbiphenyl, Pd 9], {[(phen)M]₈L ₄}(NO₃)₈ [L = 3,3′,5,5′- tetramethyl-4,4′-bipyrazolyl, Pd 3, Pt 4; 1,4-bis-4′-(3′, 5′-dimethyl)-pyrazolylbenzene, Pd 7; and 1,4-bis-4′-(3′, 5′-dimethyl)-pyrazolylbiphenyl, Pd 11], {[(bpy)Pd]₆L ₃}(NO₃)₆ [L = 1,4-bis-4′-(3′, 5′-dimethyl)-pyrazolylbenzene, 6, 10], {[(phen)-Pd]₆L ₃}(NO₃)₆ [L = 1,4-bis-4′-(3′, 5′-dimethyl)-pyrazolylbenzene, 8, 12], {[(bpy)Pd]₄L ₂}(NO₃)₄ [L = 1,3-bis-4′-(3′, 5′-dimethyl)-pyrazolylbenzene, 13, and 1,2-bis-4′-(3′, 5′-dimethyl)-pyrazolylbenzene, 15], and {[(phen)Pd]₄L ₂}(NO₃)₄ [L = 1,3-bis-4′-(3′, 5′-dimethyl)-pyrazolylbenzene, 14, and 1,2-bis-4′-(3′, 5′-dimethyl)-pyrazolylbenzene, 16] (where bpy = 2,2′-bipyridine and phen = 1,10-phenanthroline) have been synthesized through a directed self-assembly approach that involves spontaneous deprotonation of the 1H-bipyrazolyl ligands in aqueous solution. These complexes, with weak Pd(II)⋯Pd(II) or Pt(II)⋯Pt(II) interactions, have been characterized by elemental analysis, ¹H and ¹³C NMR, cold-spray ionization or electrospray ionization mass spectrometry, UV-visible spectroscopy, and luminescence spectroscopy. Complexes 1, 3, 5, 6, 14, and 15 have also been characterized by single-crystal X-ray diffraction analysis.