Five interlocked ring

Likewise, three-dimensional renderings of MIMs remind us instantly of some of the ordinary objects we encounter in our everyday lives (see Sect. 2.3). Take olympiadane [82], for example (Fig. 13), with its five interlocked rings unmistakably sharing the same topology as the Olympic logo Most catenanes bear resemblance at least to the links of a chain, as their name implies. Regardless of their resemblance to familiar objects, hundreds of beautiful crystal structures of MIMs have been produced since their debut in 1985, when Sauvage [83] published the first solid-state structure of a [2]catenane (Fig. 14a). It would be impossible to do justice to all of the beauty contained in the databank of solid-state mechanically interlocked structures. In Fig. 14 we simply present a few examples that we find noteworthy [84—88]. See Fig. 23 in Sect. 4.2 for more beautiful crystal structures of some particularly novel MIMs. 

Stoddart and co-workers transferred the strategy of template-directed synthesis to the formation of the first molecular system consisting of five interlocked rings in a linear array (Structure 51). They suggested that this [5]catenane should be called olympiadane [64]. Recently they reported the self-assembly of a new type of rotaxane, in which three side chains are linked directly to a single central core, producing a dendritic-type structure [65]. 

In 1960, van Gulick pointed out that the symbol of the International Olympics was structurally related to a pentacatenane, to which he offered the trivial name of olypiadane <93NJC619>. Thirty four years later, Stoddart et al. reported <94AG(E)1286> the first molecular compound comprised of a linear array of five interlocked rings and thus the generation of the [5]catenane... 

In 1994 J. E Stoddart and co-workers, then at the University of Birmingham (England), achieved a remarkable synthesis of a catenane containing a linear array of five interlocked rings. Because the rings are interlocked in the same way as those of the Olympic symbol, they named the compound olympiadane. 

The electrochemically triggered molecular rearrangement involves oxidation from a four-coordinate Cu to an intermediate four-coordinate Cu species which has a distinctly different ESR spectrum (higher g, lower a( Cu) measured in frozen solution) than the more stable five-coordinate Cu alternative. The latter is formed by fairly slow rotation of interlocking macrocyclic rings it reverts to the four-coordinate arrangement on re-reduction [82],... 

The carbon patterns of the products (Chart 3.1) of the drastic degradation of strychnine can all be discerned in the parent molecule but cannot by themselves be used to deduce a unique formula. That the A and B rings were six and five membered respectively was reconfirmed over the years often at the cost of considerable labour. One such case concerned dinitrostrychol-carboxylic acid, one of the nitric acid oxidation products of strychnine. It was first obtained about the turn of the century and after considerable work in the late twenties was found in the early thirties to be 5,7-dinitroindole-2-carboxylic acid. Actually the structure of strychnine would probably have been realized much earlier than it was if any one of a number of degradations had been persevered with in a systematic way. The constitution arrived at by the chemical methods rests on the properties of the functionalities in their special environments and their interlocking reactions. The advent of commercial recording infrared and ultraviolet machines played an important part in the latter phase of this work. A synthesis of the alcohol, isostrychnine I (strychnine with its cyclic ether opened at dotted line and A double bond) has confirmed these conclusions as has the determination of the structure and absolute stereochemistry by the X-ray crystallographic method. 

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