Interpretation of the electronic spectra of phthalocyanines with transition metals from quantum-chemical calculations by the density functional method

Using the time-dependent formalism of the density functional theory (time-dependent density functional theory (TDDFT)), the energies and intensities of the electronic transitions of some metal phthalocyanines of transition metals and of their anionic forms with different electron localization are studied quantum chemically. It is shown that, in all the cases studied, calculations using the B3LYP functional with even a comparatively narrow basis set (6–31G) are quite consistent with the previous calculations of the same objects by the ZINDO/S-CI semiempirical method taking into account double excitations. For a number of particular examples, it is shown that a lack of consideration of doubly excited configurations in the calculation of excited states by the TDDFT method can be compensated by the contribution from single excitations, which proves to be more significant due to the presence of the correlation component of the exchange-correlation functional.