X-ray liquidography decodes complex motions in azobenzene isomerization
Abstract
Capturing ultrafast structural rearrangements of organic molecules in solution remains a central challenge, with isomerization being a key example. Yet, despite decades of studies, a detailed atomic-level structural understanding of how isomerization occurs remains elusive for most molecules. Even for azobenzene, a textbook case of trans-cis isomerization with its deceptively simple structure of two phenyl rings linked by an azo bridge, the mechanism remains contentious. Extensive experimental and theoretical studies1-33 have proposed disparate pathways, including rotation1-15, inversion16-19, hula twist20,21 and inversion-assisted rotation22-30, without reaching consensus owing to the lack of direct structural evidence. Here we apply femtosecond X-ray liquidography to trans-azobenzene in solution and resolve, with atomic-level precision, the molecular structures of two transient intermediates bridging the trans and cis forms. The unveiled structures reveal that the trans-to-cis conversion proceeds through a sequence of distinct motions, initiated by C-N torsion, a motion that has received little attention in previous studies, and subsequently dominated by N-N rotation. This work provides structural insights into the volume-conserving nature of azobenzene isomerization and establishes X-ray liquidography as a versatile tool for molecular filming of structural dynamics in solutes lacking heavy atoms, overcoming the limitations imposed by dominant solvent scattering.
Read the paper
Related studies
- The potential and limitations of neutrons, electrons and X-rays for atomic resolution microscopy of unstained biological molecules
- X-ray-Computed Tomography Contrast Agents
- Reactivity of Surface Species in Heterogeneous Catalysts Probed by In Situ X-ray Absorption Techniques
- Single-crystal X-ray diffraction studies on structural transformations of porous coordination polymers
- Investigation of solid/vapor interfaces using ambient pressure X-ray photoelectron spectroscopy
- Resonant X-Ray Scattering Studies of Charge Order in Cuprates
Go deeper in Evidence Hub
Evidence Hub adds a study data sheet (design, sample size, evidence level, key numbers), an AI summary and a chat grounded in the paper's text.