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 se miempirical (INDO/1) self-consistent field approaches. The anion is fi rst-order Jahn-Teller distorted, and the various distortions that are possible an examined. The electronic absorption spectra of both molecu lar species and the effect that varying the degree of distortion has o n the computed anion spectrum are discussed. These results suggest tha t the four-orbital model often applied to porphyrin systems in interpr eting the low-energy spectrum is incomplete for the anion case. We fur ther conclude that the Jahn-Teller distortions calculated by either ab -initio or semiempirical models may be too great.