Orion B. Berryman

Anion–π interaction augments halide binding in solution

1H NMR spectroscopic data and complementary theoretical predictions suggest that a designed receptor exhibits the anion-pi interaction in solution.

Solution Phase Measurement of Both Weak σ and C−H···X− Hydrogen Bonding Interactions in Synthetic Anion Receptors

A series of tripodal receptors preorganize electron-deficient aromatic rings to bind halides in organic solvents using weak sigma anion-to-arene interactions or C-H...X- hydrogen bonds. 1H NMR spectroscopy proves to be a powerful technique for quantifying binding in solution and determining the interaction motifs, even in cases of weak binding.

Switchable Catalysis with a Light‐Responsive Cavitand

Host–guest systems that display catalytic behavior represent a promising area of supramolecular chemistry.[1] Supramolecular approaches to cataylst design include ligand-templated encapsulation,[2] self-assembled ligands, coordination compounds, and artificial biomacromolecules.[3] Generally, these systems operate by binding substrates and stabilizing transition states and/or increasing the effective concentration of reactive species within confined space.[4] In most catalytic host–guest systems the substrate is a guest and substrates that adequately fill the host’s interior are required to ensure activity. Alternatively, there are few instances where the guest is the catalyst.[5] These examples incorporate transition metal guests and enhanced reaction rates are rare.[6] Here we report a complementary approach where the bound guest is an organocatalyst in a deep cavitand. We find that the cavitand/piperidinium complex accelerates the Knoevenagel condensation and show that the rate of the reaction can be controlled using light to stimulate structural changes in the cavitand’s shape.

Selective recognition and extraction of the uranyl ion.

A tripodal receptor capable of extracting uranyl ion from aqueous solutions has been developed. At a uranyl concentration of 400 ppm, the developed ligand extracts ∼59% of the uranyl ion into the organic phase. The new receptor features three carboxylates that converge on the uranyl ion through bidentate interactions. Solution studies reveal slow exchange of the carboxylates on the NMR time scale. The crystal structure of the complex shows that the carboxylates coordinate to uranyl ion while the amides hydrogen bond to one of the uranyl oxo-oxygen atoms. The hydrophobic coating of the ligand and its rigidity contribute to its ability to selectively extract uranyl ion from dilute aqueous solutions.

Protonation activates anion binding and alters binding selectivity in new inherently fluorescent 2,6-bis(2-anilinoethynyl)pyridine bisureas

A new class of 2,6-bis(2-anilinoethynyl)pyridine-based bisureas forms 1 : 1 complexes with halides; protonation enhances binding by over one order of magnitude, alters the binding selectivity, and provides a colorimetric indication of anion binding.

A Halogen-Bond-Induced Triple Helicate Encapsulates Iodide.

The self-assembly of higher-order anion helicates in solution remains an elusive goal. Herein, we present the first triple helicate to encapsulate iodide in organic and aqueous media as well as the solid state. The triple helicate self-assembles from three tricationic arylethynyl strands and resembles a tubular anion channel lined with nine halogen bond donors. Eight strong iodine⋅⋅⋅iodide halogen bonds and numerous buried π-surfaces endow the triplex with remarkable stability, even at elevated temperatures. We suggest that the natural rise of a single-strand helix renders its linear halogen-bond donors non-convergent. Thus, the stringent linearity of halogen bonding is a powerful tool for the synthesis of multi-strand anion helicates.

Encapsulation of the uranyl dication

We report here the application of self-assembly to the sequestration of uranyl ion, the dominant form of uranium on Earth. The assembly presents the ion with convergent carboxylate ligands, isolates it from solvent, encapsulates it with aromatic panels and allows its extraction from aqueous solutions in the presence of excess brine.

A Deep Cavitand with a Fluorescent Wall Functions as an Ion Sensor

The synthesis and characterization of a deep cavitand bearing a fluorescent benzoquinoxaline wall is reported. Noncovalent host-guest recognition events are exploited to sense small charged molecules including acetylcholine. The cavitand also exhibits an anion dependent change in fluorescence that is used to differentiate halide ions in solution.

Uranyl ion coordination with rigid aromatic carboxylates and structural characterization of their complexes

Uranyl complexes of rigid aromatic carboxylates were synthesized and their solid-state structures characterized by X-ray crystallography. The new ligands create cavities lined with endohedral functions to encapsulate the uranyl ion.

Advantages of organic halogen bonding for halide recognition

Abstract The synthesis of a bidentate halogen bonding receptor and a nearly isostructural hydrogen bonding analogue is described. Crystal structures reveal the interactions of each receptor with anions in the solid state, while NMR titrations elucidate bidentate binding and association constants in solution. Of the two, the halogen bonding receptor demonstrates stronger, water resistant halide binding in competitive solvents.