Wavelength shifts in solid-state circular dichroism spectra: A possible explanation

We have devised an artificial sampling approach generating \absorption
flattening" (AF) on the UV–Vis spectrum of a solution of a chiral compound: Tris
(ethylendiamine)cobalt(III) chloride (L-Co(en)3Cl3). We have observed a concomitant
red shift of the CD maxima. Related CD and absorption spectra have been calculated from
spectra recorded on diluted homogeneous solutions, thus monitoring the effect of AF on
both types of data. Experimental data are in good agreement with calculated spectra. Simulations
with suitable bandshapes show that the red shift of the CD spectrum is due to
AF. On the basis of these results, we conclude that AF is an important cause of distortions
in CD spectra for inhomogeneous samples. Plans to compensate or at least to take into
account this effect are presented.