CALCULATED STRUCTURES AND ELECTRONIC ABSORPTION-SPECTROSCOPY FOR MAGNESIUM PHTHALOCYANINE AND ITS ANION-RADICAL

Structures are calculated for magnesium phthalocyanine (MgPc) and its radical anion doublet (MgPc(-)), using both ab-initio (6-31G**) and semiempirical (INDO/1) self-consistent field approaches. The anion is first-order Jahn-Teller distorted, and the various distortions that are possible an examined. The electronic absorption spectra of both molecular species and the effect that varying the degree of distortion has on the computed anion spectrum are discussed. These results suggest that the four-orbital model often applied to porphyrin systems in interpreting the low-energy spectrum is incomplete for the anion case. We further conclude that the Jahn-Teller distortions calculated by either ab-initio or semiempirical models may be too great.