Magnetic circular dichroism spectroscopy of cobalt tetraphenyltetraacenaphthoporphyrin

The first MCD spectral data for an open shell first row transition metal complex of tetraphenyltetraacenaphthoporphyrin (TPTANP) are reported. The B (or Soret) band of cobalt tetraphenyltetraacenaphthoporphyrin (CoIITPTANP(−2)) exhibits an anomalous negative Faraday A1A1 term as was reported previously in the case of ZnTPTANP, while a positive A1A1 term is observed for the Q band. INDO/1 geometry optimizations predict that the TPTANP ligand is saddled due to steric hindrance at the ligand periphery to a slightly lesser extent than is the case with ZnTPTANP. The Q and B bands of CoTPTANP arising from the π-system are blue shifted relative to those of ZnTPTANP, based on the “hypso” effect reported previously for planar porphyrin complexes of d6–9 transition metals.