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.


Physical Chemistry

Anion dimer captured within cyanostar macrocycles

Study provides first direct evidence for hydrogen-bonded anion pairs

by Jyllian Kemsley
October 31, 2016 | A version of this story appeared in Volume 94, Issue 43

Opposite charges attract and like charges repel, Coulomb’s law says. But anions can pair up and stabilize each other, according to research led by Amar H. Flood of Indiana University, Bloomington (Angew. Chem. Int. Ed. 2016, DOI: 10.1002/anie.201608118). Although indirect evidence had previously pointed to the existence of dihydrogen phosphate dimers, direct evidence was lacking. Combining macrocyclic cyanostars and bisulfate, HSO4, Flood and coworkers expected to create a complex with one bisulfate anion sandwiched in the center of two cyanostars, as already documented for perchlorate. Instead, they observed a 2:2:2 complex incorporating a pair of bisulfate anions hydrogen-bonded to each other, nestled in the centers of two stacked cyanostars and capped by tetrabutylammonium cations. The anion dimer is stabilized by hydrogen-bonding interactions to the cyanostar’s cyanostilbene-based C–H groups. The complex persists in both crystalline form and in solution, as documented by X-ray crystallography and 1H NMR. The system could point to new ways to recognize and sequester ions, the researchers say.

This image shows the structure of a bislulfate-cyanostar complex.
Credit: Amar H. Flood/Indiana University, Bloomington
A hydrogen-bonded pair of bisulfate anions (yellow = S, red = O, white = H) nestles between stacked cyanostars (blue), as shown in these side (left) and top (right) views.


This article has been sent to the following recipient:

Chemistry matters. Join us to get the news you need.