Electron diffraction (ED) is set to dramatically change technology used to determine the structure of compounds. A paper by Christopher G. Jones and colleagues at UCLA shows that MicroED can replace NMR, IR, and even X-ray diffraction for the determination of molecular structure. MicroED is clearly an advance for synthetic chemists, especially organic chemists. Plus, it works for almost every element, not just the few with magnetic dipoles required by NMR.
MicroED was originally developed to provide protein structures from frozen hydrated protein crystals that are too small for X-ray diffraction, but the authors point out MicroED can be applied to smaller molecules also.
Experimentally, MicroED involves irradiating microcrystals with a low-dose electron beam while the crystals are rotated. Electron diffraction pattern is collected as a movie in about three minutes. Conventional X-ray diffraction software for crystallography provides images of electron density in about 10–20 minutes. In many cases, hydrogens on hydrocarbons can be detected.
The speed and ease of using MicroED will certainly change how molecular structures are confirmed. With X-ray diffraction, one needs significant crystals, but with MicroED, 100-nm particles (~10–15 g) that are much smaller can be used. They do need to be crystals and not amorphous, however.
A video in the Supporting Information section shows a short movie of the MicroED experiment. See https://pubs.acs.org/doi/10.1021/acscentsci.8b00760.
Robert L. Stevenson, Ph.D., is Editor Emeritus, American Laboratory/Labcompare; e-mail: [email protected]
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