Comment on “Following molecular mobility during chemical reactions: no evidence for active propulsion” and “Molecular diffusivity of click reaction components: the diffusion enhancement question”

We provide arguments why we consider as inaccurate two recent JACS Communications which disagree with this laboratory’s report of boosted diffusion during the copper-catalyzed azide-alkyne cycloaddition click reaction (CuAAC). Fillbrook et al. claim that their diffusion NMR experiments offer no evidence for boosted diffusion, but their use of Gd3+-chelates to speed up NMR relaxations times is flawed conceptually, the authors interpreting Gd3+-chelates as inert. Actually, the same features that make gadolinium ions useful as contrast agents in magnetic resonance imaging render them unsuitable for diffusion NMR. Nonetheless, by correctly adjusting technical aspects of measurement, we confirm boosted diffusion even in the presence of this MRI contrast agent. The second skeptical Communication, by Rezaei-Ghaleh et al., compares to a reference state that is not meaningful physically.