Filming ultrafast roaming-mediated isomerization of bismuth triiodide in solution

Roaming reaction, defined as a reaction yielding products via reorientational motion in the long-range region (3 - 8 angstrom) of the potential, is a relatively recently proposed reaction pathway and is now regarded as a universal mechanism that can explain the unimolecular dissociation and isomerization of various molecules. The structural movements of the partially dissociated fragments originating from the frustrated bond fission at the onset of roaming, however, have been explored mostly via theoretical simulations and rarely observed experimentally. Here, we report an investigation of the structural dynamics during a roaming-mediated isomerization reaction of bismuth triiodide (BiI3) in acetonitrile solution using femtosecond time-resolved x-ray liquidography. Structural analysis of the data visualizes the atomic movements during the roaming-mediated isomerization process including the opening of the Bi-I-b-I-c angle and the closing of I-a-Bi-I-b-I-c dihedral angle, each by similar to 40 degrees, as well as the shortening of the I-b...I-c distance, following the frustrated bond fission.

Automated summary

Roaming reaction is a reaction pathway that yields products in the long-range potential region, explaining the unimolecular dissociation and isomerization of various molecules. This study investigates the structural dynamics during a roaming-mediated isomerization process, visualizing atomic movements following frustrated bond fission.