Pseudorotaxanes solid-state structures

Figure 4. Complexation of the hexafluorophosphate salt 2 PF6 by the macrocyclic polyether, dibenzo-24-crown-8 (1). The insets show (i) the N NMR spectrum of a 1 1 mixture of 1 and 2 PF6 in CD3CN at room temperature and (ii) the solid-state structure of the pseudorotaxane [l-2]+.

Figure 7. The [4]pseudorotaxane [(2)3-5]3+ and the [5]pseudorotaxane [(2)4-6]4+ and their solid-state structures illustrating the encapsulated PFi anions.

The solid state structure of the pyridinium-chloride pseudorotaxane Figure 8) reveals the interpenetrative nature of the components and provides evidence for anion complexation by the macrocycle s isophthalamide motif, n-n donor-acceptor interactions between the electron rich hydroquinone units of the macrocycle and... 

While the above studies are representative of the area, it should be noted that a considerable number of other [2]-pseudorotaxanes have been investigated. These include a system exhibiting enantioselective self-assembly during its formation as well as systems incorporating a new structural motif involving a l,2-bis(pyridini-um)ethane axle and a 24-crown-8 ether wheel .A number of poly-pseudoro-taxanes (and related poly-rotaxanes) as well as constitutionally asymmetric and chiral [2]-pseudorotaxanes have been reported. New, multiply-stranded and multiply-encircled systems have also been prepared. The solid state structure of... 

Scheme 29.1 Self-assembly in toluene of calix[6]arene-based wheel 1 and viologen-based axle 2 2I and solid-state structure of the resulting pseudorotaxane P[1 D 2.21]...

From the analysis of the solid-state structure of the pseudorotaxane formed by 4 and a non-symmetric axle 18 I Br (Scheme 29.6), it emerged that the calixarene wheel possesses a trigonal prism structure 1.65 nm in length with an internal width of about 0.75 nm [34]. 

Several bis(/ -phenylene)-32-crown-10-based cryptands with a variety of different moieties on the third bridge, best represented by 121, have been studied with respect to their ability to form with paraquat and bisparaquat derivatives [2]- and [3]pseudorotaxane-like structures. These inclusion complexes are observed both in the solid state (X-ray analysis) and in solution, where very high association constants have been measured by means of H NMR spectroscopy <19990L1001, 2003JA9272, 2005JOC3231, 2006CC1929>. 

Beer recently reported the anion-directed assembly of the [2]pseudorotaxane 17. In this system (see Fig. 5), a chloride anion has been employed as the central core about which two ligands (the macrocycle and the liner species) are orthogonally disposed by means of bonding to the anion. The formation of 17 was studied in solution by UV/Vis spectroscopy and H-NMR and confirmed in the solid state by an x-ray crystal structure. While chloride was demonstrated to be a good directing agent for the formation of 1. other anions such as Br. ... 

Figure5.6 The solid-state supramolecular structure of the doubly threaded, doubly encircled [4] pseudorotaxane [(BPP34C10)2(trans-2-H2)2l . Hydrogen-bonding N O,...

The above devices inspired scientists to develop solid-state MSTJ devices made from a [2]pseudorotaxane and [2]rotaxane (Figure 76) in which hydrophobic and hydrophilic regions were directly incorporated into the molecular structure to allow self-organization. ° The electrical properties were found to be highly dependent on the supramolecular structure, the presence of bistability within the (super)molecule, and the organization of the Langmuir-Blodgett film. The devices exhibited a... 

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