Solomon Knots

Figure 10.92 (a) a stylistic rendering of a Solomon knot and (b) X-ray structure of the chemical... 

Scheme 10.20 Synthetic molecular Borromean rings and a Solomon knot reported by Stoddart and coworkers. 

Scheme 10.23 The formation of a Solomon Knot (109) and a [2]catenane (111) reported by Sauvage, Fujita, and coworkers.

Fig. 12 Examples of the use of color in depictions of various types of MIMs. Note how the colors and positions of constituent parts in the three-dimensional structures reflect those in the structural drawings to enhance clarity between representations of (a) a donor-acceptor [2]catenane [75] and (b) an ammonium-binding [2]rotaxane [76] from our group, (c) a transition metal-templated Solomon Knot from the Sauvage and Fujita groups [77], and (d) a benzylic amide [2]catenane from the Leigh group [78]. Reproduced with permission from [75] (copyright 1991 Royal Society of Chemistry), [76] (copyright 2000 Wiley-VCH), [77] (copyright 1999 Royal Society of Chemistry), [78] (copyright 1995 Wiley-VCH)...

For all of the pleasure, i.e., beauty - derived from creating new interlocked architectures, we have only scratched at the surface of what is possible. Many of the molecules shown in this section were already framed in the context of beauty (Borromean Rings and Solomon Knots), and we expect that aesthetic considerations will continue to motivate new architectural developments. 

Fig. 29 Solid-state structure of the doubly interlocked [2] catenane (Solomon Knot) that emerges unexpectedly from a DCL containing DAB, DFP, and a 1 1 mixture of Zn2+ and Cu2+templates [217]...

The plant (Piper methysticum) grows best near sea level in areas like the Solomon and Fiji Islands, Samoa, Tahiti and New Guinea. With sufficient sunlight, it can reach twenty feet. The psychic components reside within the root—which after three or four years attains a thickness of three to five inches. The roots in older plants become heavy and knotted, accumulating strength and flavor. After six years, such roots may weigh twenty pounds after twenty years they may be as heavy as a hundred pounds. 

Rose LR (2005) Seeing Solomon s knot. Lois Rose, Los Angeles... 

Another class of dynamic topology is a knotted macromolecule (Fig. 39b) [266-268]. Here we limit our discussion to open knots that can be untied without breaking the covalent bonds (resembling shoelaces and neckties). We do not consider knots formed by closed strings such as Borromean ring and Solomon link (Fig. 39c, d). The knot imposes constraints on the backbone, leading to a potentially different mechanochemical response compared to unknotted cousins. 

FIGURE 17.1 Most common knots and links and theirmathematical descriptions. Left to right [2]catenane, trefoil knot, Solomon link, pentafoil (or Solomon s seal) knot, and Borromean ring. 

The structure of the trefoil knot was demonstrated by a combination of high resolution mass spectrometry, NMR experiments, and computational modeling. Interestingly, the synthesis of the trefoil knot was accomplished with a consequent 56% yield, but it was shown to be accompanied by the formation of a [2]catenane species isolated in 22% yield as well as by the larger Solomon link structure detected only in minor amounts by mass spectrometry during the course of the reaction. 

A step forward in the complexity of topological molecular objects is reached with the synthesis of molecular Solomon links that are composed of two distinct strands intertwined with four alternate crossings (Figure 17.1). As a probable consequence of their increased complexity, examples of Solomon links are less common than catenates or trefoil knots. Peinador et al. reported a series of three Solomon links obtained in a single step by the self-assembly of five components two diazapyrene based strands two Pd(en)(OTf)2 coordination complexes (en = ethylene diamine, OTf = triflate) and an electron rich cyclophane containing four phenylene groups (Scheme 11)P... 

Despite the numerous molecular topologies reported to date, it is clear that very few of the intrinsic properties of these assemblies such as the topologically unconditional chirality of trefoil knots and Solomon links or the incredible kinetic inertness of Cu(I)-based [2]catenates have been exploited. A step forward for a better understanding and use of these supramolecular assemblies resides in the availability of researchers to exploit such properties. 

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