Because they aren’t there

George Mallory tried 3 times to be the first to climb Everest dying on his last attempt. When asked why he was so obsessed, he achieved immortality by saying “because it’s there”. Chemists have spent 60 years trying to synthesize carbon nanobelts “because they aren’t there”.

Well a group of Japanese chemists finally did it [ Science vol. 356 pp. 172 -175 ’17 ] It’s not quite the ultimate belt because the 6 membered rings are staggered as they are in phenacenes –https://en.wikipedia.org/wiki/Phenacene. There are 6 three ringed phenacenes in the structure, and the diameter of the ring is 8.324 Angstroms. There is no question that they got the compound as they crystallized it and have bond lengths for all.

If you look at the paper, this is a zig zag structure rather than a linear poly anthracene. The bond lengths show that every other ring has symmetric bond lengths midway between sp2 and sp3 (e.g. it’s aromatic), while the other ring clearly is not.

It be interesting to measure the chemical shifts of the C-H bonds over the center of the ring — if they could make a paraCyclophane-type molecule bridging the diameter by a (CH2)n moiety.

As long as we’re on the subject what about putting a twist in the ring and making a mobius belt. Mobius molecules are known — http://www.scs.illinois.edu/denmark/wp-content/uploads/gp/2008/Collins-1.pdf — is a very nice review — with a lot of pictures.

The authors think that their work has potential applications — “our synthesis of carbon nanobelt 1 could ultimately lead to the programmable synthesis of single- chirality, uniform-diameter CNTs (30–32) and open a field of nanobelt science and technology”. I think they were just having fun as chemists are wont to do.

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