The structures of low-lying singlet excited states of nine π-conjugated heteroaromatic compounds have been investigated by the symmetry-adapted cluster-configuration interaction (SAC-CI) method and the time-dependent density functional theory (TDDFT) using the PBE0 functional (TD-PBE0).In particular, the geometry relaxation in some ππ* and nπ* excited states of furan, pyrrole, pyridine, p-benzoquinone, uracil, adenine, 9,10-anthraquinone, coumarin, and 1,8-naphthalimide as well as the corresponding vertical transitions, including Rydberg excited states, have been analyzed in detail. The basis set and functional dependence of the results was also examined. The SAC-CI and TD-PBE0 calculations showed reasonable agreement in both transition energies and excited-state equilibrium structures for these heteroaromatic compounds.

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.

The performances of two double hybrids, namely B2PLYP and PBE0-DH, are tested over the large GMNTK30 benchmark and compared with the results obtained with the related global hybrids, B3LYP and PBE0 with the aim of defining if there is still room for the development on nonparametrized functionals at DH level. Beyond the intrinsic interest in figures, these functionals' pairs are chosen as representative of the parametrized (B2PLYP/B3LYP) and parameter-free (PBE0-DH/PBE0) approaches to density functional theory. The obtained results show that the behavior of the double hybrids in general parallel the performances of the corresponding global hybrids, thus showing that either using a parametrized or using a nonparameterized approach to design new double hybrids, the performances are generally ameliorated with respect to the corresponding global hybrids. Nevertheless, the accuracy of B2PLYP is still higher than that of PBE0-DH, especially for thermochemistry. Albeit a link between performances and functional physics is difficult to extricate, it could be argued that this last result is not surprising since both B3LYP and B2PLYP are tuned on this last property.

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Aiming at developing an affordable and easily implementable computational protocol for routine prediction of spectral properties of rigid molecular dyes, density functional theory, and time-dependent density functional theory were used in conjunction with a vibronic coupling scheme for band shape estimate. To predict the perceived color of molecules in solution, a model has been setup linking the UV-vis spectra predicted at ab initio level to the L*a*b* colorimetric parameters. The results show that a mixed protocol, implying the use of a global hybrid functional for the prediction of adiabatic energy differences and a range separated hybrid for the prediction of potential energy curvature, allows perceived colors to be quantitatively predicted, as demonstrated by the comparison of L*a*b* colorimetric parameters obtained from computed and experimental spectra. © 2017 Wiley Periodicals, Inc.

International audienceThe performances of a family of recently developed generalized gradient approximation (GGA) functionals based on the Tognetti-Cortona-Adamo (TCA) family and making use of the gradient-regulated connection (GRAC) approach are here tested on an uncommon benchmark set for the prediction of transition state (TS) structures and energies of a series of four reactions involving an early transition metal (Zr, d (0)). This benchmark test thus represents the first step in the organometallic world in which d (n) ions allowing complex phenomena such as spin crossover represent the higher level of complexity. The results obtained show that the performances of the GRAC-xxx functionals are comparable to those of global hybrid functionals both in the prediction of reaction barriers and of structural features of TSs. More complex functional forms (such as range-separated hybrids) in average enhance the energetic features, but not necessarily the overall accuracy on calculated structures. On the other hand, and as expected, purposely developed functionals for the prediction of chemical reactivity provide both structural and energetic features in good agreement with post-HF results. The present study, besides proving the good performances of GGA functionals of the GRAC-TCA family for the prediction of TS structural parameters and energetics of metal containing systems, also underlines the importance of the use of diversified benchmark sets to allow a fair evaluation of functionals performances

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