Substituent-induced circular dichroism in phthalocyanines

Phthalocyanines with two and four optically active binaphthyl units have be en synthesized and characterized by electronic absorption, CD, and MCD spec troscopy. The chiral substituents induce CD in the in-plane polarized a and Soret bands of phthalocyanines: phthalocyanines having R and S binaphthyls show positive and negative CD, respectively. The geometries of the compoun ds were optimized at the PM3 level, and a vector coupling model for the ind uction of rotatory strength was developed. This model provides a semi-quant itative description of the CD spectra. Thus, not only the sign of the CD sp ectra but also the intensity relationship between the Sorer and QCD bands a nd, further, the shape of the QCD band were reasonably explained. The discu ssion focuses on the important role of the central hydrogen atoms.