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Calculation of exchange couplings in the electronically excited state of molecular three-spin systems

Photogenerated molecular three-spin systems, composed of a chromophore and a covalently bound stable radical, are promising candidates for applications in the field of molecular spintronics. Through excitation with light, an excited doublet state and a quartet state are generated, whereby their ener...

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Autores principales: Franz, Michael, Neese, Frank, Richert, Sabine
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The Royal Society of Chemistry 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9629084/
https://www.ncbi.nlm.nih.gov/pubmed/36382276
http://dx.doi.org/10.1039/d2sc04701b
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author Franz, Michael
Neese, Frank
Richert, Sabine
author_facet Franz, Michael
Neese, Frank
Richert, Sabine
author_sort Franz, Michael
collection PubMed
description Photogenerated molecular three-spin systems, composed of a chromophore and a covalently bound stable radical, are promising candidates for applications in the field of molecular spintronics. Through excitation with light, an excited doublet state and a quartet state are generated, whereby their energy difference depends on the exchange interaction J(TR) between the chromophore triplet state (T) and the stable radical (R). In order to establish design rules for new materials to be used in molecular spintronics devices, it is of great importance to gain knowledge on the magnitude of J(TR) as well as the factors influencing J(TR) on a molecular level. Here, we present a robust and reliable computational method to determine excited state exchange couplings in three-electron-three-centre systems based on a CASSCF/QD-NEVPT2 approach. The methodology is benchmarked and then applied to a series of molecules composed of a perylene chromophore covalently linked to various stable radicals. We calculate the phenomenological exchange interaction J(TR) between chromophore and radical, which can be compared directly to the experiment, but also illustrate how the individual exchange interactions J(ij) can be extracted using an effective Hamiltonian that corresponds to the Heisenberg–Dirac–Van-Vleck Hamiltonian. The latter procedure enables a more detailed analysis of the contributions to the exchange interaction J(TR) and yields additional insight that will be invaluable for future design optimisation.
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spelling pubmed-96290842022-11-14 Calculation of exchange couplings in the electronically excited state of molecular three-spin systems Franz, Michael Neese, Frank Richert, Sabine Chem Sci Chemistry Photogenerated molecular three-spin systems, composed of a chromophore and a covalently bound stable radical, are promising candidates for applications in the field of molecular spintronics. Through excitation with light, an excited doublet state and a quartet state are generated, whereby their energy difference depends on the exchange interaction J(TR) between the chromophore triplet state (T) and the stable radical (R). In order to establish design rules for new materials to be used in molecular spintronics devices, it is of great importance to gain knowledge on the magnitude of J(TR) as well as the factors influencing J(TR) on a molecular level. Here, we present a robust and reliable computational method to determine excited state exchange couplings in three-electron-three-centre systems based on a CASSCF/QD-NEVPT2 approach. The methodology is benchmarked and then applied to a series of molecules composed of a perylene chromophore covalently linked to various stable radicals. We calculate the phenomenological exchange interaction J(TR) between chromophore and radical, which can be compared directly to the experiment, but also illustrate how the individual exchange interactions J(ij) can be extracted using an effective Hamiltonian that corresponds to the Heisenberg–Dirac–Van-Vleck Hamiltonian. The latter procedure enables a more detailed analysis of the contributions to the exchange interaction J(TR) and yields additional insight that will be invaluable for future design optimisation. The Royal Society of Chemistry 2022-09-19 /pmc/articles/PMC9629084/ /pubmed/36382276 http://dx.doi.org/10.1039/d2sc04701b Text en This journal is © The Royal Society of Chemistry https://creativecommons.org/licenses/by-nc/3.0/
spellingShingle Chemistry
Franz, Michael
Neese, Frank
Richert, Sabine
Calculation of exchange couplings in the electronically excited state of molecular three-spin systems
title Calculation of exchange couplings in the electronically excited state of molecular three-spin systems
title_full Calculation of exchange couplings in the electronically excited state of molecular three-spin systems
title_fullStr Calculation of exchange couplings in the electronically excited state of molecular three-spin systems
title_full_unstemmed Calculation of exchange couplings in the electronically excited state of molecular three-spin systems
title_short Calculation of exchange couplings in the electronically excited state of molecular three-spin systems
title_sort calculation of exchange couplings in the electronically excited state of molecular three-spin systems
topic Chemistry
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9629084/
https://www.ncbi.nlm.nih.gov/pubmed/36382276
http://dx.doi.org/10.1039/d2sc04701b
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