Coupled cluster calculations provide a one-to-one mapping between calculated and observed transition energies in the electronic absorption spectrum of zinc phthalocyanine

Abstract

© 2017 Wiley Periodicals, Inc. All transitions in the experimentally designated and numbered Q, B, and N bands ( < 4.8 eV) of the electronic absorption spectrum of zinc phthalocyanine (ZnPc) are assigned on the basis of one-to-one agreement between calculated and experimentally observed transition energies and oscillator strengths. Each band in this range of the spectrum represents a ligand-based transition that originates from a combination of occupied orbitals and terminates in the lowest unoccupied molecular orbital (LUMO,). Transition energies in the L and C regions (4.8–6.5 eV) are harder to capture quantitatively, due to the partial Rydberg character of some of the excited states, and so are tentatively assigned here. Most transitions in this range correspond to excitations from the HOMO or lower-energy orbitals to π orbitals above the LUMO.