Dispersion of anomalous azimuthal rotation and circular extinction contrast in dyed K2SO4 crystals

Abstract

We present measurements of the dispersion of anomalous azimuthal rotation signals from dyed crystals that are at variance with our predictions based on a model of these effects predicated on the predominance of Rayleigh scattering from isolated dye molecules (Kaminsky et al. J Phys Chem A 107:2800-2807, 2003). Here, we extend our scattering model to include the effects of the absorption and refraction of individual dyes that are inclined in a biased manner with respect to the eigenmodes of the medium. Our revised model describes the wavelength dependence of the rotations. It is likely that absorption, refraction, and Rayleigh scattering are all manifest, with absorption and refraction being the leading effects.

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

“…We also examined dyed potassium sulfate crystals whose mirror image-related faces may incorporate conformationally chiral guest molecules enantioselectively during growth. With these crystals, we did not observe CD but rather a new optical phenomenon called anomalous circular extinction (ACE) when measured by differential circular polarization or anomalous azimuthal rotation (AAR) when measured in incident linearly polarized light (LPL) . ACE and AAR can arise when strong oscillators are oriented and rotated in the same sense with respect to the eigenmodes of the anisotropic medium in which they are embedded, a circumstance sometimes encountered in dyed crystals .…”

“…ACE and AAR can arise when strong oscillators are oriented and rotated in the same sense with respect to the eigenmodes of the anisotropic medium in which they are embedded, a circumstance sometimes encountered in dyed crystals . Unlike intrinsic optical rotation and CD, ACE and AAR , provide no evidence of absolute molecular configuration but may be used instead to determine the absolute orientation of adsorbed dye molecules and thereby resolve an ambiguity present in polarized absorption measurements . Here, we compare ACE from crystals of lithium potassium sulfate (LiKSO 4 ) colored by Chicago sky blue (CSB), a dye with a chiral ground state conformation, and by pyranine (PYR), a dye with a rigidly achiral π-system.…”

Experimental aspects of solid state circular dichroism

“…The idea of a dedicated CD microscope was tried in the past, 12 with questionable results, but the dream has been made possible by the innovative development of a CD imaging microscope, [13][14][15] the idea behind this has also been patented. 16 Both approaches, together with the sister HAUP technique [17][18][19] (High Accuracy Universal Polarimetry) make use of a rather different hardware from the common CD spectrometers.…”

Dendritic crystal growth, differential circular scattering, and the origin of biomolecular homochirality

“…Scientists have subsequently worked out many mechanisms of chiral discrimination of molecules by crystal surfaces. [27][28][29][30][31][32][33][34][35] Others have taken advantage of the chirality of crystal surfaces to achieve practical aims such as heterogeneous asymmetric catalysis. 36 The use of high index metal surfaces in this regard has become an explosive theme.…”