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.

A supramolecular system that switches reversibly, via three different states, through electrochemical adjustment of the guest properties of tetrathiafulvalene (TTF) has been developed. 1H NMR, luminescence, and absorption spectroscopies, in conjunction with LSI mass spectrometry, X-ray crystallography, and cyclic/differential pulse voltammetries, established that the π-electron-accepting (EA) tetrathiafulvalenium dication (TTF2+) binds strongly within the cavity of the π-electron-donating (ED) macrocyclic polyether 1,5-dinaphtho[38]crown-10 (1/5DN38C10), generating a host−guest complex that is stabilized by, inter alia, π−π stacking interactions. Comparable techniques have also demonstrated that neutral tetrathiafulvalene (TTF(0)) acts as an ED guest when it complexes with the EA tetracationic cyclophane cyclobis(paraquat-p-phenylene) (CBPQT4+). On the other hand, the tetrathiafulvalenium radical cation (TTF+•) is not bound by either of the hosts CBPQT4+ or 1/5DN38C10. Electrochemical experiments revealed that the three-component mixture CBPQT4+−1/5DN38C10−TTF behaves as a reversible three-pole supramolecular switch, since, depending on the potential range, TTF can be (1) free (in the TTF+• state), (2) included within the cavity of CBPQT4+ (as TTF(0)), or (3) complexed with 1/5DN38C10 (in the TTF2+ state). The system's three-pole behavior has interesting implications in relation to the design of electrochromic displays and devices capable of controlling energy- or electron-transfer processes between selected components.