With crystals in the news thanks to the award of the 2011 Nobel Prize in Chemistry to Dan Shechtman for his 1982 discovery of quasicrystals, it is quite timely that I was writing about another crystalline discovery just before the announcement. This one is from US chemist George Richter-Addo of the University of Oklahoma and his team who have demonstrated that crystals need not necessarily be as solid as once thought. The existence of a new type of “flexible” crystal hints at new understanding as well as relying on a novel technique that might be used to probe matter more deeply than ever before: Flexible Crystals.
I asked Mathias Senge of Trinity College Dublin to give me a perspective on Richter-Addo’s work:
“This is a very noteworthy contribution by Richter-Addo’s group and certainly worth being highlighted,” he says. “Any structural chemist will immediately see the implications of this work and it will serve as a route map for how to investigate small (gaseous) molecule interactions with coordination compounds.”
“More importantly this might reignite interest in solid state, crystal, chemistry in general. I personally think that this might be on par with advances made in time-resolved X-ray crystallography. While the latter might be of more general relevance, the gas-diffusion approach is easier and can be reproduced and used by any chemist.”
He adds that the specific compounds investigated by Richter-Addo’s team, porphyrins, the molecules at the heart of oxygen-carrying haemoglobin in the blood, might provide inspiration to others. “I can even see that people might go back to investigations of the (then) groundbreaking picket fence porphyrins from Collman and have a second look at interactions [between iron and carbon monoxide, and oxygen]. Perhaps its even possible to get similar effects with porphyrin-protein crystals,” he adds.
“Likewise, what George described in his paper using X-ray crystallography might be easily extended to similar studies with resonance Raman spectroscopy, looking at changes in the core conformation, and then the same spectroscopic method can be used to identify what goes on in biological samples (proteins).”
Xu, N., Powell, D., & Richter-Addo, G. (2011). Nitrosylation in a Crystal: Remarkable Movements of Iron Porphyrins Upon Binding of Nitric Oxide Angewandte Chemie International Edition, 50 (41), 9694-9696 DOI: 10.1002/anie.201103329