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| Olympicene Source: IBM Zurich | BBC |
Olympicene, a tight five-ringed structure, does indeed resemble the famous logo of the quadrennial international contest. IBM Zurich, who used specially-functionalized AFM tips to image pentacene in 2009, now brings us fantastic high-res images of this polycycle (see right).
I won't go into the story behind the science, as that's been elegantly summarized in a number of places already. Instead, I want to highlight a perplexing 'teaser line' from yesterday's ChemConnector post:
"You can see the Olympicene compound coming together step by step and yes, the final step is not yet reported!"OK. Let's see, we have the first few steps laid out for us, thanks to RSC's ChemSpider. Easiest way to make anything? Start with most of it intact! From commercial 1-pyrenecarboxaldehyde, a Wittig olefination, H2 reduction, basic ester hydrolysis, chlorination, Friedel-Crafts, and lithium aluminum hydride (LAH) reduction brings us to the 5-ringed alcohol (shown below). All the steps are greater than 89% yield, except the F/C (15%), which one imagines might make the "other" pentacene isomer preferentially.
I find the final "Top Secret" step amusing, because any organic chemist "familiar with the art" could think of at least five ways to do it! (Non-chemist readers: the molecule on the left needs a single C=C double bond, and standing in the way is just a molecule of water). That alcohol is fairly "activated" for elimination. My guess? A little strong acid, gentle heat, and some molecular sieves.
Pro Tip: Don't believe the hype declaring olympicene the "smallest 5-ringed structure," at just 1.2 nm across. Skeptics, cynics should check their bond lengths. Is olympicene smaller than cubane? (6 rings, ~0.6 nm). How about a ladderane? (5 rings, ~1 nm). Anyone know other molecules that might qualify?
Updates (04:18, 5/29/12) - ChemConnector mentions, via Twitter, that the step is less 'Top Secret,' and more not-yet-drawn-up for ChemSpider Synthetic Pages. Per Excimer's comment, fixed the position of the 'saturated' CH2 carbon.
(21:10, 5/31/12) - Commenter (And U. Warwick Prof!) Peter Scott points out the new ChemSpider page, showing major isomer and detailing conditions.
Updates (04:18, 5/29/12) - ChemConnector mentions, via Twitter, that the step is less 'Top Secret,' and more not-yet-drawn-up for ChemSpider Synthetic Pages. Per Excimer's comment, fixed the position of the 'saturated' CH2 carbon.
(21:10, 5/31/12) - Commenter (And U. Warwick Prof!) Peter Scott points out the new ChemSpider page, showing major isomer and detailing conditions.
You'd be amazed what *doesn't* work in PAH synthesis- almost as amazing as what does. Also, the unsaturated carbon is on one of the outer carbons- would be quite strained otherwise. I look forward to see if unicorn blood actually worked.
ReplyDelete@Excimer - Fixed the image, thanks! Also, want to suggest some standard PAH conditions? Thanks!
ReplyDeleteIs the news story here that IBM just recently imaged it? IMHO, olympiadane is much cooler, and it's been around since '94.
ReplyDeleteYes, but olympiadane is not flat.
ReplyDeleteand olympicene has been around since 1965. it's not claimed by any scientist to be new.
ReplyDeleteWell, don't tell the authors in the press release that! They claim it's never before been synthesized. The story, as its told, suggests that David Fox and Graham Richards thought it up, "doodled it" onto a whiteboard, and realized no one had ever made it by total synthesis.
ReplyDelete@Anon8:24 - You said 1965....was it detected in soot, or something?
I don't recall anyone from our side ever saying it hadn't been synthesized before. I know I've seen this said on one of the many posts this weekend (but cannot find it at present) but I certainly don't think that David Fox believes it is the first synthesis. I found the compound in patents early on in the project and the fact it was on ChemSpider commonly (not always) means it has been synthesized. We've certainly never claimed first synthesis. Only that we challenged the community to come up with a way to synthesize is and put the synthetic steps on ChemSpider Synthetic Pages so people could see the details of the synthesis in an "open environment".
ReplyDeleteIt is common that Press Releases then get picked up and rewritten by reporters. The number of changes I have seen over the weekend is quite funny...broken telephone effect. In one blog they made the microscopist the synthetic chemist...amazing how messages get modified...there's a blog post there and I will summarize a lot of this in the next couple of days. Thanks for your post!
@AJW - Thanks for writing in! The passage I'm thinking of, from the Warwick release (http://www2.warwick.ac.uk/newsandevents/pressreleases/smallest_five_rings)
ReplyDelete""When doodling in a planning meeting, it occurred to me that a molecular structure with three hexagonal rings above two others would make for an interesting synthetic challenge," said Professor Graham Richards CBE, RSC Council member.
"I wondered: could someone actually make it, and produce an image of the actual molecule?"
Chemists at the University of Warwick, Dr David Fox and Anish Mistry, used some clever synthetic organic chemistry - the modern molecule designer's toolbox - to build olympicene."
I think that accurately captures Graham's thought process...those are his words. What we did not do was check for whether it had been synthesized before but based on David Fox's blog post here: http://www.huffingtonpost.com/david-fox/olympic-rings-molecule_b_1551144.html they did check. He commented " The best recipe for the molecule dated from the 1960s and the authors did not know exactly what they had made."
DeleteFinally a retrosynthesis I can understand! ;-)
ReplyDeleteI'm afraid the main site for the CH2 in solution is at the central carbon cssp.chemspider.com/542
ReplyDeleteThanks for the heads up...will change soon as I'm able.
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