A very simple self-assembling system, which produces inclusion complexes with pseudorotaxane geometries, is described. The self-assembly of eight pseudorotaxanes with a range of stoichiometries-I : I , 1 :2, 2:1, and 2:2 (host:guest)-has been Keywords achieved. These pseudorotaxanes self-assemble from readily available componentscrown ethers -dialkylammonium well-known crown ethers, such as dibenzo [24]crown-8 and bis-p-phenylene[34lcrown-salts 9 hydrogen bonding -molecular 10, and secondary dialkylammonium hexafluorophosphate salts, such as (PhCH,),-recognition -pseudorotaxanes * NHiPF; and (nBu),NHlPF;-and have been characterized not only in the solid state, self-assembly but also in solution and in the "gas phase". The pseudorotaxanes are stabilized largely by hydrogen-bonding interactions and, in some instances, by aryl-aryl interactions.

A simple motif for molecular recognition—the binding of disubstituted ammonium salts, for example dibenzyl‐ and di‐n‐butylammonium hexaflurophosphate, with crown ethers like dibenzo[24]crown‐8—results in the self‐assembly of threaded 1:1 complexes 1. The superstructures of these complexes are stabilized by hydrogen bonds, electrostatic pole–dipole interactions, and dispersive interactions.

On account of its pivotal role in several essential chemical and biological processes, anion binding and recognition ['] is currently arousing considerable attention within the domain of supramolecular chemistry.['] Traditionally, supramolecular chemists have positioned anion recognition sites within covalent macro(po1y)cyclic framework^^^] in a preorganizedL4] manner, so as to achieve strong anion binding. However, the discovery of self-a~sembled[~~ superniolecules that are capable of binding anions has been accomplished,[61 as supramolecular science has developed. Nevertheless, to the best of our knowledge, there has been no report to date of a self-assembled anion receptor whose components are held together entirely by hydrogen bonds. We describe here the discovery of two novel supermoleculesself-assembled utilizing only hydrogen bonds-which display either partial or complete envelopment of PF, ions in the solid state.Recently, we reportedL7] that macrocyclic polyethers form inclusion complexes, termed pseudorotaxanes,[*I of varying stoichiometries with secondary dibenzylammonium ions. In these pseudorotaxanes the ammonium ions are threaded through the macrorings and are held in place by a combination of

Vier‐ und Fünfkomponenten‐Pseudorotaxane, die durch das Einfädeln von Dibenzylammoniumionen in makrocyclische Polyether entstehen, verhalten sich als Anionenrezeptoren. Die Präorganisation der positiv geladenen Erkennungsstellen in diesen Überstrukturen induziert im Festkörper die Komplexierung eines PF6−‐Anions. Dieses ist im dreisträngigen Vierkomponenten‐Pseudorotaxan nur teilweise eingelagert, in der größeren Bindungstasche des viersträngigen Fünfkomponenten‐Pseudorotaxans (siehe Bild rechts) hingegen völlig eingehüllt.

The self-assembly of three new rotaxanes-two[2]rotaxanes and a [3]rotaxane-formed by a "threading followed by stoppering" approach is described. These template-directed syntheses rely on the formation of pseudorotaxane intennediates, which self-assemble in solution from functionalized secondary dialkylammonium hewafluorophosphate threads and macrocyclic polyether rings (either dibenzo-[24]crown-8 or its asymmetric constitutional isomer). The stoppers-substituted 1,2,3-triazoles-were created by thermally allowed 1,3-dipolar cycloadditions between azido groups, which terminate the threads, and di-tert-butyl acetylenedicarboxylate. lar

No abstract

Two new [2]rotaxane-based molecular shuttles, in which a mechanically bound dibenzo[24]crown-8 (DB24C8) macroring shunts back and forth between two dialkylammonium recognition sites situated on a chemical dumbbell, have been constructed by a novel synthetic strategy that relies upon the use of the tert-butoxycarbonyl (Boc) protecting group. During the syntheses of both molecular shuttles, this protecting group masks a dialkylammonium recognition center which is liberated only after the [2]rotaxane constitution is established. In both cases, the molecular shuttles' other dialkylammonium center is essential for the rotaxane-forming reactions and it ensures that DB24C8 is interpenetrated by threadlike precursors, as a result of noncovalent bonding interactions, to produce [2]pseudorotaxanes which are stoppered subsequently through 1,3-dipolar cycloadditions between azides and bulky acetylenedicarboxylates. The new molecular shuttles have been examined by means of dynamic 1H NMR spectroscopy, which reveals that the movements of the DB24C8 macroring are very highly dependent both on solvent properties and on the nature of the spacer unit linking the two dialkylammonium centers. Thus, DB24C8 shunts facilely between the dialkylammonium centers when the shuttles are dissolved in solvents that readily donate their nonbonding electrons into noncovalent bonds, e.g., DMF, and when spacer units that do not offer much steric resistance to shuttling, e.g., hexamethylene, are used. On the other hand, shuttling is difficult in solvents that are less inclined to donate their electrons into noncovalent bonds, e.g., (CDCl2)2, and when relatively bulky benzenoid spacer units, e.g., p-xylylene, link the two dialkylammonium centers. It has been proposed that the DB24C8 might act as a "ferry" which carries a proton between dialkylammonium and dialkylamine moieties in a singly protonated [2]rotaxane by means of ion-dipole interactions.

90.67(2)", V = 1675 A3, 2 = 2, p,,.,. = 1.54 p(CuKJ = 21.4 em-', 4216 unabhangige Reflexe, 2411 davon beobachtetmit IF,I > 4u(~FJ). 28 <110",Verfeinerung zu R = 0.138, R, = 0.157. Siemens-P4/PC-Diffraktometer fur 3 ' 2PF6 und 4 4PF6 und Siemens-P4/