ADVERTISEMENT
2 /3 FREE ARTICLES LEFT THIS MONTH Remaining
Chemistry matters. Join us to get the news you need.

If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.

ENJOY UNLIMITED ACCES TO C&EN

Materials

Giant Porphyrin Goes Big On Aromaticity

Structure And Bonding: Expanded porphyrin ring with 50 π electrons sets a new record for largest aromatic molecule

by Stephen K. Ritter
May 4, 2015 | APPEARED IN VOLUME 93, ISSUE 18

By increasing the number of pyrrole groups in a porphyrin ring from the usual four to 12, an international team of chemists has succeeded in making the largest aromatic molecule known to date (Chem. Eur. J. 2015, DOI: 10.1002/chem.201500650). Expanding the realm of aromaticity is nothing new for Dongho Kim of South Korea’s Yonsei University and Atsuhiro Osuka of Japan’s Kyoto University. Their groups have been collaborating for a few years to make big aromatic porphyrins in the quest to study anion and metal binding and electrochromic effects. In their latest effort, the researchers used a tripyrrole building block to construct a [52π]dodecaphyrin, a porphyrin ring consisting of a dozen connected pyrrole groups and adorned with pentafluorophenyl groups. This conjugated molecule has 52 π electrons and is nonaromatic—it doesn’t obey Hückel’s rule of possessing 4n + 2 π electrons. To meet the criterion, the team oxidized the molecule with a benzoquinone to form a [50π]dodecaphyrin, which bests the former aromaticity record holder, a [46π]decaphyrin the groups made last year. Subsequently protonating the [50π]dodecaphyrin using methanesulfonic acid helped flatten the molecule and improve its electron delocalization, thereby enhancing its aromaticity further.

[+]Enlarge
Credit: Chem. Eur. J.
This tetraprotonated dodecaphyrin, with 50 π electrons, has set a new record for aromaticity.
09318-scicon-combined-564.jpg
Credit: Chem. Eur. J.
This tetraprotonated dodecaphyrin, with 50 π electrons, has set a new record for aromaticity.
X

Article:

This article has been sent to the following recipient:

Leave A Comment

*Required to comment