(βR,β‘R)-dimethylmesobilirubin-XIIIα, an optically
active synthetic analogue of bilirubin, the yellow pigment
of jaundice, and xanthobilirubinat, a dipyrrinone analogue for one-half
of a rubin pigment, dissolved in the
nematic liquid crystal ZLI 1695, have been studied by means of UV−vis
polarized absorption and circular
dichroism (CD) spectroscopy. The order parameters have been
evaluated from the temperature dependence
of the degree of anisotropy. The method of “vanishing spectral
features” has also been taken into consideration.
The reduced absorption spectra have been obtained. It has
been found that the orientational properties as
well as the polarization of the absorption bands of the two compounds
are quite different. Moreover, the
UV−vis absorption and CD spectra of
β,β‘-dimethylmesobilirubin-XIIIα have been interpreted on the
basis
of the exciton coupling model, assuming the point symmetry group
C
2. The orientation of the principal
axes
of the orientational distribution tensor (order tensor) with respect to
the molecular frame has been determined.
That the anisotropic CD (ACD) spectra are not very different from
the CD spectra can be understood from
the spectroscopic analysis taking into account the orientational
order.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.