High-Level Ab Initio Computations of the Absorption
Spectra of Organic Iridium Complexes
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Abstract
The excited states of fac-tris(phenylpyridinato)iridium
[Ir(ppy)<sub>3</sub>] and the smaller model complex Ir(C<sub>3</sub>H<sub>4</sub>N)<sub>3</sub> are computed using a number of high-level
ab initio methods, including the recently implemented algebraic diagrammatic
construction method to third-order ADC(3). A detailed description
of the states is provided through advanced analysis methods, which
allow a quantification of different charge transfer and orbital relaxation
effects and give extended insight into the many-body wave functions.
Compared to the ADC(3) benchmark an unexpected striking difference
of ADC(2) is found for Ir(C<sub>3</sub>H<sub>4</sub>N)<sub>3</sub>, which derives from an overstabilization of charge transfer effects.
Time-dependent density functional theory (TDDFT) using the B3LYP functional
shows an analogous but less severe error for charge transfer states,
whereas the ωB97 results are in good agreement with ADC(3).
Multireference configuration interaction computations, which are in
reasonable agreement with ADC(3), reveal that static correlation does
not play a significant role. In the case of the larger Ir(ppy)<sub>3</sub> complex, results at the TDDFT/B3LYP and TDDFT/ωB97
levels of theory are presented. Strong discrepancies between the two
functionals, which are found with respect to the energies, characters,
as well as the density of the low lying states, are discussed in detail
and compared to experiment
