Circular Extinction Imaging: Determination of the Absolute Orientation of Embedded Chromophores in Enantiomorphously Twinned LiKSO4 Crystals

Crystal Growth & Design, 5 (6), 2117 -2123, 2005. 10.1021/cg050145n S1528-7483(05)00145-2
Web Release Date: August 30, 2005

Circular Extinction Imaging: Determination of the Absolute Orientation of Embedded Chromophores in Enantiomorphously Twinned LiKSO₄ Crystals

Kacey Claborn, An-Shyang Chu, Sei-Hum Jang, Fengyu Su, Werner Kaminsky,* and Bart Kahr*

Department of Chemistry, P.O. Box 351700, University of Washington, Seattle, Washington 98195-1700

Received April 12, 2005

Revised July 8, 2005

Abstract:

Crystals of lithium potassium sulfate dyed during growth with Chicago sky blue or pyranine were investigated with a recently developed circular extinction imaging microscope originally intended for capturing circular dichroism. The resulting micrographs provide evidence of anomalous circular extinction, an effect that can arise when strong oscillators embedded in an otherwise homogeneous, anisotropic medium are oriented and rotated in the same sense with respect to the eigenmodes of the host. Our images reflect the previously determined twin laws in LiKSO₄ and establish the assignment of the absolute orientation of the dye molecules in the crystal, a supramolecular stereochemical subtlety that we have long struggled with.

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