title: Absolute configuration of chiral [2.2]paracyclophanes with intramolecular charge-transfer interaction. Failure of the exciton chirality method and use of the sector rule applied to the cotton effect of the CT transition.
abstract: Optically active 4,7-dicyano-12,15-dimethoxy[2.2]paracyclophanes have been separated by chiral HPLC and their absolute configurations determined by comparison of the experimental and the theoretical VCD spectra. X-ray crystallographic structures for both diastereomers are also reported. The electronic circular dichroism spectra of these enantiomeric pairs, as chiral intramolecular charge-transfer complexes, have been obtained for the first time. The exciton coupling method, usually used for determining the absolute configuration of chiral molecules, however, did not give a correct prediction for the present CT-paracyclophane system. Instead, empirical sector rules for the signs of the Cotton effects of the CT transition can be applied for the assignment of the absolute configuration.
authors.affiliation: Department of Molecular Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita 565-0871, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Furo
authors.forename: Tadashi
authors.initials: T
authors.lastname: Mori
authors.forename: Takehiko
authors.initials: T
authors.lastname: Wada
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Inoue