Electronic Spectra of the Aluminum(III) Complexes of 5,10,15,20-Tetraphenylporphin and 2,3,7,8,12,13,17,18-Octaethylporphin

Absorption, magnetic circular dichroism (MCD) and emission spectra as well as preparations of the aluminum(III) complexes of 5,10,15,20-tetraphenylporphin (TPP) and 2,3,7,8,12,13,17,18-octaethylporphin (OEP) are presented. On the basis of the spectral observations, the molecular parameters to describe the lowest (π,π*) excited states of a typical metal porphyrin with only minor perturbation by the incorporated tervalent metal ion were determined. The orbital angular momenta in the excited states were evaluated from the MCD spectra as follows: TPPAlCl, Λz=3.0 h in Q00 band, Λz=±0.61 h Ti in B band and OEPAlCl, Λz=±0.61 h Ti in Q00 band, Λz=0.557 h in band. A Davydov splitting of the Soret band observed for the μ-oxo dimer was interpreted in terms of the exciton coupling between two parallel porphyrin chromophores.