Chapter 6: Circular Dichroism Induced by Optically Active Binaphthyl

Chiral 1,1’-binaphthyl (BINAP) moieties have been used to study the asymmetric synthesis of porphyrinoids, since the BINAP π-system provides a well defined asymmetric field, which interacts with the porphyrinoid π-system in a manner that can be readily predicted. Two types of BINAP-substituted phthalocyanine (Pc) structure are considered, with either two or four BINAP moieties linked to the Pc chromophore via sulfur or oxygen atoms. Since the mutual alignments of the Pc and BINAP rings are firmly fixed, a detailed analysis of the induced circular dichroism (ICD) intensity observed for the lowest energy Q band of the achiral Pc π-system can be carried out based on a consideration of the intensity arising from the Kuhn-Kirkwood and “CD stealing” intensity mechanisms. No other example of this type of ICD system has been reported to date, but the analysis outlined demonstrates that this approach has considerable potential if properly applied to other chromophores.