Simultaneous Prediction of the Energies of Qx and Qy Bands and Intramolecular Charge-Transfer Transitions in Benzoannulated and Non-Peripherally Substituted Metal-Free Phthalocyanines and Their Analogues: No Standard TDDFT Silver Bullet Yet

An insight into the electronic structure of the metal-free, unsubstituted, and nonperipherally substituted with electron-donating groups tetraazaporphyrin (H(2)TAP), phthalocyanine (H2Pc), naphthalocyanine (H(2)Nc), anthracocyanine (H2Ac) platforms has been gained and discussed on the basis of experimental UVvis and MCD spectra as well as density functional theory (DFT), time-dependent DFT (TDDFT), and semiempirical ZINDO/S calculations. Experimental data are suggestive of potential crossover behavior between the 1(1)B(2u) and 1(1)B(3u3u) excited states (in traditional D-2h notation) around 800 nm. A large array of exchange-correlation functionals were tested to predict the vertical excitation energies in H(2)TAPs, H(2)Pcs, H(2)Ncs, and H(2)Acs both in gas phase and solution. In general, TDDFT-predicted energies of the Q(x) and Q(y) bands and the splitting between them correlate well with the amount of HartreeFock exchange present in a specific exchange-correlation functional with the long-range corrected LC-BP86 and LC-wPBE functionals providing the best agreement between theory and experiment. The pure GGA (BP86) exchange-correlation functional significantly underestimated, while long-range corrected LC-BP86 and LC-wPBE exchange-correlation functionals and semiempirical ZINDO/S method strongly overestimated the intramolecular charge-transfer (ICT) transitions experimentally observed for -OR, -SR, and -NR2 substituted at nonperipheral position phthalocyanines and their analogues in the 450-650 nm region. The hybrid CAM-B3LYP, PBE1PBE, and B3LYP exchange-correlation functionals were found to be much better in predicting energies of such ICT transitions. Overall, we did not find a single exchange-correlation functional that can accurately (MAD < 0.05 eV) and simultaneously predict the energies and the splittings of the Q(x) and Q(y) bands as well as energies of the ICT transitions in a large array of substituted and unsubstituted metal-free phthalocyanines and their benzoannulated analogues