Electronic Circular Dichroism Imaging Casts a New Light on the Origin of Solid-State Chiroptical Properties
December 2021
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Studysummary This study found that the observed isotropic ss-ECD spectrum of finasteride is influenced by the anisotropy of locally oriented crystals, offering new possibilities for analyzing solid-state chiral materials.
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The research paper discusses a study on the solid-state Electronic Circular Dichroism (ss-ECD) spectra of a model microcrystalline solid, finasteride, dispersed into a KCl pellet. The researchers used the synchrotron radiation source at the Diamond B23 beamline and scanned a surface of 36 mm2 with a step of 0.5 mm. They found that the ECD imaging (ECDi) spectra were very different from each other and from the ss-ECD recorded with a bench-top instrument. This difference is due to the anisotropic part of the ECD (ACD), which averages to zero in solution or on a large number of randomly oriented crystallites, but can otherwise be extremely large. The study concluded that the observed isotropic ss-ECD spectrum is governed by the anisotropy of locally oriented crystals, introducing a new quality for ss-ECD measurements and opening a new future for probing and mapping chiral materials in the solid state such as active pharmaceutical ingredients (APIs).
