Abstract
The template-directed syntheses of the bipyridinium-based cyclophanes cyclobis(paraquat-p-phenylene) and cyclobis(paraquat-4,4'-biphenylene) can be achieved by employing π-electron rich hydroquinone-based and ferrocene-based templates. By employing macrocyclic hydroquinone-based polyether templates, [2]catenanes and [3]catenanes, in which the bipyridinium-based cyclophane is mechanically-interlocked with the macrocyclic template(s), can be self-assembled in solution. The introduction of ester functions within these polyether chains of the macrocyclic templates provides the possibility of degrading the catenated structure via ester hydrolysis, thus, releasing the tetracationic cyclophane originally trapped within the catenane. The use of ferrocene-based templates provides a more efficient way to synthesise the bipyridinium-based cyclophane incorporating bitolyl spacers. In particular, the use of a 1,1'-disubstituted polyether ferrocene derivative provides the possibility of obtaining the tetracationic cyclophane, cyclobis(paraquat-4,4'-biphenylene) - accessible only in very low yields, without the use of a template - on a preparative scale.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 313-322 |
| Number of pages | 10 |
| Journal | Pure and Applied Chemistry |
| Volume | 68 |
| Issue number | 2 |
| DOIs | |
| State | Published - Feb 1996 |
Funding
The self-assembly of the bipyridinium-based cyclophanes 3*4PFg and 9*4PFg around x-electron rich hydroquinone-based and ferrocene-based templates has been achieved by relying upon noncovalent bonding interactions such as n-x stacking between the complementary aromatic units, CH.a.0 hydrogen bonding and edge-to-face T-type interactions. By employing acyclic templates (Figure 5), pseudorotaxane-like complexes can be self-assembled in solution. Their decomplexation releases the free cyclophane and the unchanged template which can be recycled. In particular, the use of a 1.1'-disubstituted ferrocene derivative provides the possibility of obtaining the tetracationic cyclophane, cyclobis(paraquat-4.4'-biphenylene) - accessible only in very low yield without the use of a template - on a preparative scale. When appropriate macrocyclic polyethers are employed as the templates (Figure 3,[ 2]catenanes and [3]catenanes can be self-assembled in acetonitrile solution at room temperature. Thus, the tetracationic cyclophanes are trapped within the catenated structures as a result of mechanical linkages with the x- electron rich macrocyclic component(s). The introduction of ester functions within the polyether chains of the macrocyclic templates provides a way of generating degradable catenanes. Subsequent ester hydrolyses of the macrocyclic lactones incorporated within the catenated structures afford, after the destruction of the catenane, the free bipyridinium-based component in a quantitative yield. Complex formation between ferrocene-based derivatives and the bipyridinium-based cyclophane 9*4PF6 opens up possibilities of generating electrochemically-active (36-39) catenanes, rotaxanes and pseudorotaxanes having potential device-like (40,41) characteristics. Acknowledgements. This research was supported in the UK by the European Community Human Capital and Mobility Programme and by the Engineering and Physical Sciences Research Council.
ASJC Scopus subject areas
- General Chemistry
- General Chemical Engineering