Concerted Halogen-Bonded Networks with <i>N</i>‑Alkyl Ammonium Resorcinarene Bromides: From Dimeric Dumbbell to Capsular Architectures

<i>N</i>-Alkyl ammonium resorcinarene bromides and 1,4-diiodooctafluorobutane via multiple intermolecular halogen bonds (XB) form different exotic supramolecular architectures through subtle changes of the upper rim substituents. Dimeric dumbbell-like assembly with encapsulated guest molecules is generated with <i>N</i>-benzyl substituents. The <i>N</i>-hexyl groups engender an XB-induced polymeric pseudocapsule and an XB-induced dimeric capsule with entrapped 1,4-dioxane guest molecules. The <i>N</i>-propyl and <i>N</i>-cyclohexyl groups generate deep cavity cavitands. The deep cavity cavitands possess cavities for self-inclusion leading to polymeric herringbone arrangement in one direction and that pack into 3D polymeric arrangement resembling egg crate-like supramolecular networks. These assemblies are studied in solution via NMR spectroscopy and in the solid state via X-ray crystallography

Guest-Induced Folding of the <i>N</i>‑Benzyl Substituents in an Ammonium Resorcinarene Chloride and the Formation of a Halogen-Bonded Dimer of Capsules

In methanol, <i>N</i>-benzyl ammonium resorcinarene chloride (Bn-NARCl) crystallizes as a solvate with the benzyl groups oriented in an open flower-like manner parallel to the cation–anion seam. 1,4-Dioxane as guest triggers a “semi-closed” single-molecule capsule with two benzyl “arms” enclosing the guest. The introduction of halogen bond (XB) donor 1,4-diiodoperfluorobutane (1,4-DIOFB) additionally folds the remaining two benzyl arms thus resulting in a fully closed capsule. Two 1,4-DIOFB molecules bridge two such Bn-NARCl capsules, forming a 2:2:2 XB held dimeric assembly of single-molecule capsules. The peculiar behavior was not observed in the bromide analog under similar experimental conditions. The studies were performed in solid state by X-ray single crystal crystallography, and MM level theoretical calculations

Bamboo-like Chained Cavities and Other Halogen-Bonded Complexes from Tetrahaloethynyl Cavitands with Simple Ditopic Halogen Bond Acceptors

Halogen bonding provides a useful complement to hydrogen bonding and metal-coordination as a tool for organizing supramolecular systems. Resorcinarenes, tetrameric bowl-shaped cavitands, have been previously shown to function as efficient scaffolds for generating dimeric capsules in both solution and solid-phase, and complicated one-, two-, and three-dimensional frameworks in the solid phase. Tetrahaloethynyl resorcinarenes (bromide and iodide) position the halogen atoms in a very promising “crown-like” orientation for acting as organizing halogen-bond donors to help build capsules and higher-order networks. Symmetric divalent halogen bond acceptors including bipyridines, 1,4-dioxane, and 1,4-diazabicyclo[2.2.2]­octane are very promising halogen bond accepting partners for creating these systems. This report describes the complex structures arising from combining these various systems including self-included dimers, herringbone-packed architectures enclosing medium (186 ų) cavities, and a very intriguing bamboo-like one-dimensional rod with large (683 ų) cavities between adjacent dimeric units. These various structures, all organized through host–host, host–acceptor, and host–solvent interactions highlight the emergent complexity of these types of complexes. As halogen bonds are weaker than hydrogen-bonds, the resulting architectures are harder to predict, and these results provide additional insight into the parameters requiring consideration when designing crystalline supramolecular systems using halogen-bonds as the core organizing principle

Host-guest complexes of C-propyl-2-bromoresorcinarene with aromatic <i>N</i>-oxides^*

<p>The host-guest complexes of C-propyl-2-bromoresorcinarene with pyridine <i>N</i>-oxide, 3-methylpyridine <i>N</i>-oxide, quinoline <i>N</i>-oxide and isoquinoline <i>N</i>-oxide are studied using single crystal X-ray crystallography and ¹H NMR spectroscopy. The C-propyl-2-bromoresorcinarene forms <i>endo</i>-complexes with the aromatic <i>N</i>-oxides in the solid-state when crystallised from either methanol or acetone. In solution, the <i>endo</i>-complexes were observed only in methanol-d₄. In DMSO the solvent itself is a good guest, and crystallisation provides only solvate <i>endo</i>-complexes. The C-propyl-2-bromoresorcinarene shows remarkable flexibility when crystallised from either methanol or acetone, and packs into one-dimensional self-included chains. Of special note, crystallising C-propyl-2-bromoresorcinarene with 3-methylpyridine <i>N</i>-oxide from acetone results in a 2:2 dimeric capsular assembly organised through both C−H···π_host and N−O···(H−O)_host interactions.</p

Recognition of Viologen Derivatives in Water by <i>N</i>‑Alkyl Ammonium Resorcinarene Chlorides

Three water-soluble <i>N</i>-alkyl ammonium resorcinarene chlorides decorated with terminal hydroxyl groups at the lower rims were synthesized and characterized. The receptors were decorated at the upper rim with either terminal hydroxyl, rigid cyclohexyl, or flexible benzyl groups. The binding affinities of these receptors toward three viologen derivatives, two of which possess an acetylmethyl group attached to one of the pyridine nitrogens, in water were investigated via ¹H NMR spectroscopy, fluorescence spectroscopy, and isothermal titration calorimetry (ITC). ITC quantification of the binding process gave association constants of up to 10³ M^–1. Analyses reveal a spontaneous binding process which are all exothermic and are both enthalpy and entropy driven