Application of MCD spectroscopy to porphyrinoids

Magnetic circular dichroism (MCD) spectroscopy has proven invaluable in the assignment of the optical spectra of the porphyrinoids over the last 40 years. Recently, with new power of the DFT theoretical treatments available routinely, the assignment of porphyrinoid spectra has become an important factor in the correct interpretation of the electronic structure predicted by the calculations. In this review, we have described in detail the formalism required to use the MCD technique to probe the electronic structure of porphyrinoid complexes. We begin with a detailed description of the optical background to the technique; continue by describing the current theoretical interpretation of the spectral morphology, and end by describing the analysis of the MCD spectral data for a number of porphyrins and phthalocyanines.