Article

Ab initio electronic and optical spectra of free-base porphyrins: The role of electronic correlation

European Theoretical Spectroscopy Facility (ETSF), University of Rome Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma, Italy.
The Journal of Chemical Physics (Impact Factor: 2.95). 09/2009; 131(8):084102. DOI: 10.1063/1.3204938
Source: PubMed

ABSTRACT

We present a theoretical investigation of electronic and optical properties of free-base porphyrins based on density functional theory and many-body perturbation theory. The electronic levels of free-base porphine (H(2)P) and its phenyl derivative, free-base tetraphenylporphyrin (H(2)TPP) are calculated using the ab initio GW approximation for the self-energy. The approach is found to yield results that compare favorably with the available photoemission spectra. The excitonic nature of the optical peaks is revealed by solving the Bethe-Salpeter equation, which provides an accurate description of the experimental absorption spectra. The lowest triplet transition energies are in good agreement with the measured values.

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Questions & Answers about this publication

  • Conor Hogan added an answer in Porphyrins:
    Does anyone know how to calculate UV-VIS spectrum of Q bands of free base porphyrin?

    For two years I tried to obtain the full absorption spectrum of free base porphyrin. So far, I used the TD-DFT/6-31G ++ (d,p) (Gaussian 09) method and also methods mentioned before:

    https://www.researchgate.net/post/Appropriate_method_and_basis_set_to_calculate_absorption_spectrum2

    Unfortunately, so far I get only with a good accuracy the Soret and two Q bands but I can't get 4 Q bands. I know that electronic transitions in the other two bands are not allowed, but in several publications I have seen that it is possible to obtain.

    I would be greateful for any help and any detail that could help me to solve my problem.

    Tadeusz

    Conor Hogan

    Hi Tadeusz,
    For an alternative (solid state theoretical physics) approach, you might be interested to look at our papers on H2P:
    https://www.researchgate.net/publication/26784944_Ab_initio_electronic_and_optical_spectra_of_free-base_porphyrins_The_role_of_electronic_correlation
    https://www.researchgate.net/publication/234140956_Correlation_effects_in_the_optical_spectra_of_porphyrin_oligomer_chains_Exciton_confinement_and_length_dependence
    but also in this case, we do not include vibronic coupling and so also find just two Q bands.
    Regards,
    Conor

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