Spectra of porphyrins: Part II. Four orbital model

Abstract Porphyrin molecules are treated by combining an LCAO-MO (Huckel) calculation with a simplified treatment of configuration interaction. The Huckel calculation requires special parameters α N = α C + 2 β CC and β CN = 0.5 β CC for certain internal porphyrin nitrogen atoms. The configuration interaction parameters are determined on Zn tetraphenylporphin. Calculations are carried out for reduced porphyrins, azaporphins, and benzporphins. Spectra are predicted, and chemical and magnetic properties are discussed.

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