[M8L4]8+-Type Squares Self-Assembled by Dipalladium Corners and Bridging Aromatic Dipyrazole Ligands for Iodine Capture.

Square-like metallamacrocyclic palladium(II) complexes [M8L4]8+ (1-7) were synthesized by reacting aromatic dipyrazole ligands (H2L1-H2L3 with pyromellitic arylimide-, 1,4,5,8-naphthalenetetracarboxylic arylimide-, and anthracene-based aromatic groups, respectively) with dipalladium corners ([(bpy)2Pd2(NO3)2](NO3)2, [(dmbpy)2Pd2(NO3)2](NO3)2, or [(phen)2Pd2(NO3)2](NO3)2, where bpy = 2,2'-bipyridine, dmbpy = 4,4'-dimethyl-2,2'-bipyridine, and phen = 1,10-phenanthroline) in aqueous solutions via metal-directed self-assembly. Metallamacrocycles 1-7 were fully characterized by 1H and 13C nuclear magnetic resonance spectroscopy and electrospray ionization mass spectrometry, and the square structure of 7·8NO3- was further confirmed via single crystal X-ray diffraction. These square-like metallamacrocycles exhibit effective performance for iodine adsorption.

Interconversion of Highly Entangled Polyhedra into Concave Polyhedra by Nitrate-Induced Ternary Coordination.

Entangled (M3 L2 )n polyhedral complexes represent a unique class of supramolecular architectures that are stabilized by relatively weak metal-acetylene interactions in cooperation with conventional metal-pyridyl coordination. Counter-anion exchange of these complexes with a nitrate (NO3 - ) ion triggered formal metal insertion between the metal centers, and a heteroleptic ternary coordination mode with acetylenic, pyridyl, and nitrate donors was generated on the metal centers. As a result, the main frameworks of the polyhedral complexes M18 L12 and M12 L8 were formally extended into a new series of concave polyhedra having the compositions M21 L12 and M13 L8 , respectively. This transformation also resulted in the local disconnection of the highly entangled trifurcate topology of the framework, providing clues toward the skeletal editing of extended and complex three-dimensional (3D) architectures.

Amplification of weak chiral inductions for excellent control over the helical orientation of discrete topologically chiral (M3L2) n polyhedra.

Superb control over the helical chirality of discrete (M3L2) n polyhedra (n = 2,4,8, M = CuI or AgI) created from the self-assembly of propeller-shaped ligands (L) equipped with chiral side chains is demonstrated here. Almost perfect chiral induction (>99 : 1) of the helical orientation of the framework was achieved for the largest (M3L2)8 cube with 48 small chiral side chains (diameter: ∼5 nm), while no or moderate chiral induction was observed for smaller polyhedra (n = 2, 4). Thus, amplification of the weak chiral inductions of each ligand unit is an efficient way to control the chirality of large discrete nanostructures with high structural complexity.

Self-Assembly and C-H⋠⋠⋠Anion Hydrogen Bonding of Palladium(II)-based Metallacalixarenes Using Pyridyl- or Phenyl-Bridged Di-Naphthoimidazoles.

Metal-directed self-assembly approaches led to the formation of two novel boat-shaped palladium(II)-based metallacalixarenes 1 (1 a, 1 b and 1 c) and 2 (2 a, 2 b and 2 c), by using the two new ligands 2,6-bis(1H-naphtho[2,3]imidazol-1-yl)pyridine (L1 ) and 1,3-bis(1H-naphtho[2,3]imidazol-1-yl)benzene (L2 ) with cis-coordinated PdII precursor (tmeda)Pd(ONO2 )2 (tmeda=N, N, N', N'-tetra-methylethylenediamine), repectively. All complexes with different counterions were systematically characterized in solution, and their structures were determined by X-ray single crystallography analyses in the solid state. The crystal architectures were subtly regulated among different anions through two types (inter- and intra-)molecular C-H hydrogen bonding interactions and other weak interactions. The anion complexation with the two metal-assembled anion receptors were further investigated in solution.

Self-Assembly of Water-Soluble Platinum(II)-Based Metallacalixarenes and Tuning Their Conformational Interconversion via Synergistic Effects between Solvents and Anions.

The aqueous self-assembly of the flexible ligand L bis(1H-benz[d]imidazole-1-yl)methane and cis-coordinated PtII precursors [(en)Pt2+ , (tmeda)Pt2+ , en=ethylenediamine, tmeda=N,N,N',N'-tetramethylethylenediamine)] led to the formation of the metallacalixarenes with full alternative conformations (e.g., two novel water-soluble metallacalixarenes [M2 L2 ]4+ and [M3 L3 ]6+ with D2 and D3 symmetry, respectively). Their molecular structures were determined by single crystal X-ray analyses in solid state. The two metallacalixarenes present different cavity sizes and the [M3 L3 ]6+ cavity encapsulates one NO3 - . NOESY NMR revealed that the conformational interconversion between 1,3-alternate conformer in methanol and cone conformer in DMSO was tuned via the synergistic effect between solvent and anion. Guest encapsulation is also discussed.

Self-assembly of metallomacrocycles with dipyrazole ligands and anion sensing of [Pd4Fe2] macrocycle with ferrocene-based dipyrazole ligand.

By employing dipalladium corners [(bpy)(2)Pd(2)(NO(3))(2)](NO(3))(2) or [(phen)(2)Pd(2)(NO(3))(2)](NO(3))(2) (where bpy = 2,2'-bipyridine and phen = 1,10-phenanthroline) to bridge ferrocene-based dipyrazole ligand (L(1)) and m-phenylene-based dipyrazole ligands (L(2-3)) in aqueous solution, a series of positively-charged [M(4)L(2)](4+) metallomacrocycles were obtained. Their structures were characterized by (1)H NMR, electrospray ionization mass spectrometry (ESI-MS), elemental analysis, and single crystal X-ray diffraction analysis for 1·4NO(3) ({[(bpy)Pd](4)L(1)(2)}(NO(3))(4)) and 4·4NO(3) ({[(phen)Pd](4)L(2)(2)}(NO(3))(4)). In their single crystal structures, NO(3)(-) anions are located at the dipalladium corners by C-H...O hydrogen bonds. Importantly, the anion-sensing properties of ferrocene functionalized [Pd(4)Fe(2)] hetero-metallomacrocycle 1 were investigated in acetonitrile by SWV, CV and NMR analysis, showing promise for Br(-) sensing.