Singlet‐Triplet Excited‐State Inversion in Heptazine and Related Molecules: Assessment of TD‐DFT and ab initio Methods
| Autor: | Juan Carlos Sancho-García, Emilio San-Fabián, Yoann Olivier, Gaetano Ricci |
|---|---|
| Přispěvatelé: | Universidad de Alicante. Departamento de Química Física, Química Cuántica |
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Heptazine
electron correlation effects exchange interaction Ab initio Electron correlation effects 02 engineering and technology 010402 general chemistry 01 natural sciences Heptazine derivatives heptazine derivatives singlet-triplet energy gap chemistry.chemical_compound Ab initio quantum chemistry methods Molecule Singlet state Química Física Physical and Theoretical Chemistry Wave function Physics Exchange interaction ab initio calculations Singlet-triplet energy gap 021001 nanoscience & nanotechnology Atomic and Molecular Physics and Optics 0104 chemical sciences chemistry Chemical physics Excited state Ab initio calculations 0210 nano-technology |
| Zdroj: | RUA. Repositorio Institucional de la Universidad de Alicante Universidad de Alicante (UA) |
| Popis: | We have investigated the origin of the S1-T1 energy levels inversion for heptazine, and other N-doped π-conjugated hydrocarbons, leading thus to an unusually negative singlet-triplet energy gap (DEST < 0). Since this inversion might rely on substantial doubly-excited configurations to the S1 and/or T1 wavefunctions, we have systematically applied multi-configurational SA-CASSCF and SC-NEVPT2 methods, SCS-corrected CC2 and ADC(2) approaches, and linear-response TD-DFT, to analyse if the latter method could also face this challenging issue. We have also extended the study to B-doped π-conjugated systems, to see the effect of chemical composition on the results. For all the systems studied, an intricate interplay between the singlet-triplet exchange interaction, the influence of doubly-excited configurations, and the impact of dynamic correlation effects, serves to explain the DEST < 0 values found for most of the compounds, which is not predicted by TD-DFT. The work in Alicante is supported by “Ministerio de Ciencia e Innovación” of Spain (Grant No. PID2019-106114GB–I00). Computational resources in Namur are provided by the “Consortium des Équipements de Calcul Intensif” (CÉCI), funded by the “Fonds de la Recherche Scientifiques de Belgique” (F.R.S.-F.N.R.S.) under Grant No. 2.5020.11. G.R. acknowledges a grant from the “Fonds pour la formation a la Recherche dans l’Industrie et dans l’Agriculture” (F.R.I.A.) of the F.R.S.-F.N.R.S. |
| Databáze: | OpenAIRE |
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