Influence of terminal substituents on the halide anion binding of foldamer-based receptors

Foldamers 1–4 incorporating different terminal substituents have been designed and synthesized for binding halide anions.~1H NMR titration experiments carried out in DMSO-d_6/CDCl_3（15/85, v/v）demonstrated that the short oligo （aryltriazole）s backbone 1 could not bind halide anions unless that amide H-bond donors were incorporated at the termini of the oligomer. Terminal substituents on oligo（aryltriazoleamide）s foldamers 2–4 display a considerable influence on the binding affinities of the foldamers for halide anions. Large steric hindrance of the terminal substituents was found to be unfavorable for binding halide anions, but aromatic π-π interactions between two terminal substituents are capable of stabilizing the conformation of foldamers thus giving rise to an enhancement in the binding strengths. However, the terminal substituents were found to hardly affect the binding selectivity in the studied cases.

Neutral C–H bond vs. electron pair of N(sp^2): A binding site effect study of macrocycle anion receptor

To evaluate the effect of neutral C–H bond or electron pair of nitrogen atom with sp2hybridization（N（sp2）） involving into the same chemical environment for anion binding, two analogous tetracationic imidazolium macrocycles, namely cyclo[2]（2,6-bis-（1H-imidazol-1-yl）pyridine） [2]（1,3-dimethylenebenzene）（14＋）, and cyclo[2]（2,6-bis-（1H-imidazol-1-yl）pyridine）[2]（2,6-di methylenepyridine）（24＋）were studied in detail as small inorganic anion receptors. The guest anions with different shapes are Cl,N3, NO3, and H2PO4. The host–guest interactions were characterized via1 H NMR spectroscopy,electrospray ionization mass spectrometry（ESI-MS） and single crystal X-ray crystallography. The results implied that macrocyclic hosts with similar backbone but two distinct binding sites（14＋with neutral C–H vs. 24＋with N（sp2）） vary markedly in their response to anions, including the binding modes and association constants. The finding will serve to the construction of new anion receptors, even improve insights into the anion binding process in biology.

Crystal Structures of Fluoride and Chloride Complexes of Tris[(2-benzimidazolyl)methyl]amine

The crystal structures of fluoride and chloride complexes of tris[（2-benzimidazolyl）methyl]amine 1 were characterized by X-ray crystallography. 1 adopts （73 symmetrical geometry and cone-like conformation so as to allow its three NHs to associate with the anions through hydrogen bonds. Despite the different sizes of the anions, the two crystals are unexpectedly isostructural. The binding ability of the anions of 1 in solution was also studied by using of UV-vis spectroscopy.

Structure of [Co(im)6]SiF6：Short Hydrogen Bonds Involving SiF62- Ions

A new complex C（18）H（24）CoF6N（12）Si has been synthesized by the reaction of cobalt（II） fluoride tetrahydrate with imidazole in a glass vessel. SiF62-was generated by in situ reaction of fluoride on silica. This complex has been characterized by different techniques such as elemental analysis, IR studies, magnetic measurements, electronic absorption measurements and single-crystal X-ray structure determination. The crystals are hexagonal in the R-3 space group, with a = 13.225（6）, b = 13.225（6）, c = 12.517（11） A, and g = 120°. In complex [Co（im）6]SiF6, the cobalt atom is six-coordinated to adopt a regular octahedral geometry and the SiF62-ion acts as the counter anion. The crystal displays a network structure and SiF62- bridging hexagram formation by N-（39）···F-Si interactions between imdazole and SiF62-. SiF62-plays an important role in assembling the supramolecular aggregates.

Naphthalene-Pillared Benzene Triimide Cage: An Efficient Receptor for Polyhedral Anions and a General Tool for Probing Theoretically-Existing Anion-π Binding Motifs

A triangular prism cage 2 with benzene triimide(BTI)as the base and 2,7-naphthalene dimethylene as the supporting pillars was designed and synthesized efficiently.The two parallel BTI planes constitute a cavity of 7.58Åwhich allows the inclusion of anions of various sizes.

Unprecede nted tunable hydrophobic effect and anion recognition triggered by AIE with Hofmeister series in water

An un precedented tun able hydrophobic effect in self-assembly of a small cationic organic fluorophore(NI-TPy^(+))-based with aggregation-induced emission(AIE)property was realized in aqueous solution.The amplification of hydrophobicity was found to be significantly dependent upon the increasing aggregates of NI-TPy^(+),which enabled the study of the hydrophobic binding of chaotropic anions with the Hofmeister series.

Sulfate Binding with a Tripodal Tris（4-pyridylurea） Receptor

The tris（2-aminoethyl）amine （tren）-based tris（4-pyridylurea） receptor L has been synthesized and its anion binding properties were studied. The ligand forms a 2 ： 1 （host/guest） complex with MgSO4, [SO4^2 L2], in which a sulfate ion is encapsulated by six urea groups from the two ligands through multiple hydrogen bonds. The metal ions do not coordinate to the pyridyl groups but exist as the hydrate [Mg（H2O）6]2＋ and interact with the [SO4 L2] capsules in the outer coordination sphere to form a three dimensional extended structure. The anion binding behav- ior of ligand L in solution was studied.