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Theoretical and Experimental Investigations of Circular Dichroism and Absolute Configuration Determination of Chiral Anthracene Photodimers
journal contribution
posted on 2016-02-21, 17:50 authored by Ayako Wakai, Hiroki Fukasawa, Cheng Yang, Tadashi Mori, Yoshihisa InoueSubstituted anthracenes photodimerize to stereoisomeric
[4 + 4]
cyclodimers, some of which are inherently chiral. Recent supramolecular
photochirogenic studies enabled the efficient preparation of specific
stereoisomers, the absolute configurations of which should reflect
the chiral environment of supramolecular host or scaffold employed
but have not been determined, hindering detailed mechanistic elucidation
and further host/scaffold design. In this study, we performed the
combined experimental and state-of-the-art theoretical analyses of
the circular dichroism spectra of chiral cyclodimers of 2-anthracenecarboxylic
and 2,6-anthracenedicarboxylic acids to reveal the configurational
and molecular orbital origin of the Cotton effects observed, and unambiguously
determined the absolute configurations of these chiral cyclodimers.
The present results allow us to directly correlate the enantiotopic
face-selectivity upon photocyclodimerization with the absolute configuration
of the cyclodimer derived therefrom and also to precisely elucidate
the chiral arrangement of two cyclodimerizing anthracenes.