Benchmark Study on the Triplet Excited-State Geometries and Phosphorescence Energies of Heterocyclic Compounds: Comparison Between TD-PBE0 and SAC-CI

Abstract

In this work, we investigated the properties of the triplet excited states of heterocyclic compounds including their geometries, electronic properties, and phosphorescence energies by using both the direct symmetry-adapted cluster-configuration interaction (SAC-CI) method and the TD-DFT approach with the PBE0 exchange-correlation functional (TD-PBE0). The target states are the ππ* and nπ* triplet states of furan, pyrrole, pyridine, p-benzoquinone, uracil, adenine, 9,10-anthraquinone, coumarin, and 1,8-naphthalimide as well as the Rydberg states. The present benchmark demonstrates that these two methods provide reasonably accurate geometries for the excited states of these heterocyclic compounds. The calculated Stokes shifts, which reflect geometry changes, were consistent for both these methods. The trends of agreement with experimental or reference values obtained for a panel of exchange-correlation functionals used to compute the absolute emission energies from the triplet states, differ from those found for the singlet excited states. Some of the low-lying triplet excited states were examined in detail for the first time, including vibrational analysis.

Theoretical Rationalization of the Singlet–Triplet Gap in OLEDs Materials: Impact of Charge-Transfer Character

“…[69][70][71] In the case of charge-transfer excitations, one could better use modern range-separated hybrid functional such as ωB97X. 72 However, since one deals here with intramolecular charge-transfer excitations, the E V A (S 1 ) values are systematically overestimated by around 0.8 − 0.9 eV with this functional, in agreement with previous studies.…”

Absolute cross sections for electronic excitation of furan by electron impact

“…We favor an assignment as the 3 (π 3 ,3s) Rydberg state because we fail to observe the peak moving to the left on an energy-loss scale with increasing residual energy, as a peak due to a resonance, locked to a given incident energy, should [26]. The assignment of the 5.66-eV peak as the [27] and the value of 5.69 eV calculated by Gavrilov et al [21]. This assignment also supports the conclusion of Palmer et al [18], who interpreted a downward shift of the 6.04-eV band at their spectra recorded with a trap depth of 0.1 eV (i.e., low residual energy) as due to the 3 (π 3 ,3s) state, which they placed at 5.8 eV.…”

Accurate Excited-State Geometries: A CASPT2 and Coupled-Cluster Reference Database for Small Molecules

“…26 This work certainly represented a huge computational effort at that time, but symmetry constraints were imposed in some cases (e.g., C 2 v for the lowest ES of acetone) and the compact 6-31G(d) atomic basis set was used for most compounds. Ten years later, symmetry-adapted cluster–configuration interaction (SAC–CI) structures have been obtained with a polarized double-ζ atomic basis set, namely, D95(d,p), by Bousquet and co-workers for both the singlet 23 and triplet 24 ES of medium-sized compounds: furan, pyrrole, pyridine, p -benzoquinone, uracil, adenine, coumarin, 9,10-anthraquinone, and 1,8-naphthalimide. Again, symmetry constraints were imposed in both these works to avoid conical intersections, though frequency calculations (CIS level) were carried out to ascertain the nature of the optimized states.…”