X-ray liquidography decodes complex motions in azobenzene isomerization.

Femtosecond X-ray liquidography reveals that azobenzene isomerization proceeds via C-N torsion and N-N rotation, clarifying the molecular pathway with atomic precision.

• Why it matters: Understanding the detailed mechanisms of molecular isomerization is crucial for designing photoresponsive materials and biological systems, yet direct structural evidence has been lacking.
• What they did: The study employed femtosecond X-ray liquidography to capture transient intermediates of trans-azobenzene in solution, identifying two key structures that bridge the trans and cis forms.
• The result: Findings demonstrate that azobenzene undergoes a volume-conserving isomerization initiated by C-N torsion and dominated by N-N rotation, advancing the understanding of molecular motion and showcasing X-ray liquidography’s capabilities.