Doubts About Unclick Reaction

Science has published an editorial expression of concern about a high-profile polymer mechanochemistry paper that appeared in the journal in 2011. The report, “Unclicking the Click: Mechanically Facilitated 1,3-Dipolar Cycloreversions” (DOI: 10.1126/science.1207934), was authored by Christopher W. Bielawski, Johnathan N. Brantley, and Kelly M. Wiggins of the University of Texas, Austin.

In the paper, the chemists reported they could mechanically pull apart a 1,2,3-triazole—the product of the most popular of the so-called click reactions. Neither thermal nor photochemical conditions are able to spur this cycloreversion, but Bielawski and his students reported that they were able to pull the triazole apart by tethering it between two poly(methyl acrylate) chains and then subjecting it to ultrasound.

Science Editor-in-Chief Marcia McNutt writes that in response to a reader e-mail, Bielawski revisited the original data. “In over 50% of the figure parts, the authors deemed the data unreliable due to uncertainty regarding the origin of data or the manner in which the data were processed,” McNutt notes.

Bielawski tells C&EN that a former group member, whom he declined to identify, came forward and admitted to manipulating data in the Science paper. Bielawski says that his lab “repeated the experiments in question and found that the conclusions of the report were unchanged.” He has submitted a correction to Science to address the concerns. Neither Brantley nor Wiggins could be reached for comment. The University of Texas, Austin, is conducting an investigation.

The 2011 Science paper was important for the field of polymer mechanochemistry because it showed how mechanical forces can open new reaction pathways using a popular reaction, comments Rint P. Sijbesma, a mechanochemistry expert at Eindhoven University of Technology, in the Netherlands. “That there is now significant doubt as to the veracity of the results will have consequences for the understanding of this specific reaction. But the general principles of mechanochemically induced reactivity and the unique nature of mechanically facilitated reaction pathways stand firm because they are based on a much larger body of experiments with a wide range of reactions.”