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: 3.12). 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.

2 Bookmarks
 · 
112 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report here the results from theoretical calculations of the potential energy curves, the geometry optimizations, and the electronic structures for three dimers of lithium phthalocyanine (LiPc) by using three types of functional systems: PBE1PBE, B3LYP, and M06. The results were discussed in comparison with those obtained for the dimers of magnesium phthalocyanine (MgPc). The long-range dispersive interactions were considered in part using these functional systems in the increasing order of PBE1PBE, B3LYP, and M06. The mechanism whereby the dispersive interactions affect the geometric and electronic structures of the LiPc and MgPc dimers is discussed. The calculated results provide insight into the computational methods for both open- and closed-shell metal phthalocyanine (MPc) dimers: Although the PBE1PBE and B3LYP functional systems cannot evaluate a weak dispersion interaction appropriately, the M06 functional can estimate a weak dispersion interaction well in both open- and closed-shell MPc dimers. Basis set superposition error (BSSE) corrections play an important role for the quantitative analysis; however, the calculation results without BSSE corrections may be sufficient for the qualitative discussion on the properties of these dimers such as geometries, stabilities, electronic structures, and so on.
    Journal of Computational Chemistry 07/2011; 32(14):3062-7. · 3.84 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The fundamental and optical gaps of relevant molecular systems are of primary importance for organic-based photovoltaics. Unfortunately, whereas optical gaps are accessible with time-dependent density functional theory (DFT), the highest-occupied – lowest-unoccupied eigenvalue gaps resulting from DFT calculations with semi-local or hybrid functionals routinely and severely underestimate the fundamental gaps of gas-phase organic molecules. Here, we show that a range-separated hybrid functional, optimally tuned so as to obey Koopmans’ theorem, provides fundamental gaps that are very close to benchmark results obtained from many-body perturbation theory in the GW approximation. We then show that using this functional does not compromise the possibility of obtaining reliable optical gaps from time-dependent DFT. We therefore suggest optimally tuned range-separated hybrid functionals as a practical and accurate tool for DFT-based predictions of photovoltaically relevant and other molecular systems.
    Physical Review B 08/2011; 84(7). · 3.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The present investigation reports for the first time a detailed theoretical analysis of the optical absorption spectra of corannulene-based materials using state-of-the-art first-principles many-body GW-BSE theory. The study specifically addresses the nature of optical excitations for predictions regarding suitability for device fabrication. The well-defined structure-correlation relationship in functionalized corannulenes is used in a focused investigation of the predicted optoelectronic properties in both the isolated state and bulk crystals. The findings suggest that the excitonic properties are strongly dependent on the specific substituent group as well as the crystalline arrangement. Arylethynyl-substituted corannulene derivatives are shown to be the most suitable for device purposes.
    Journal of the American Chemical Society 08/2011; 133(35):14002-9. · 10.68 Impact Factor

Full-text (2 Sources)

View
31 Downloads
Available from
May 16, 2014