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Published on: February 7, 2022
Light-Assisted Akamptisomerization: Excited-State Bond-Angle Reflection (ESBAR) as a Molecular Photoswitching Element
Karine N de Andrade1, Jhonathan Rosa de Souza2,3, Paula Homem-de-Mello2
1Department of Organic Chemistry, Institute of Chemistry, Universidade Federal Fluminense, Outeiro de São João Batista, Niterói, Rio de Janiero 24020-141, Brazil.
Akamptisomerism in porphyrins can be facilitated in the excited state. Excited-state bond-angle reflection (ESBAR) lowers the energy barrier, suggesting potential photoswitching applications.
Area of Science:
- * Inorganic Chemistry
- * Photochemistry
- * Theoretical Chemistry
Background:
- * Akamptisomerism, a form of isomerism, arises from bond-angle reflection (BAR) at a B-O-B bridge in low-symmetry B2OF2 porphyrins.
- * This phenomenon leads to isolable diastereomers in the ground electronic state.
Purpose of the Study:
- * To conduct the first theoretical investigation of excited-state bond-angle reflection (ESBAR).
- * To explore the potential of ESBAR as a photoswitching mechanism in porphyrinoid systems.
Main Methods:
- * Time-Dependent Density-Functional Theory (TD-DFT) calculations were employed.
- * Activation barriers for BAR in the ground state (S0) and triplet excited state (T1) were computed.
Main Results:
- * The BAR activation barrier significantly decreases from 21.3 kcal mol-1 in S0 to 15.3 kcal mol-1 in T1.
- * Near-isoenergetic singlet and triplet states and enhanced spin-orbit coupling support the feasibility of singlet-triplet intersystem crossing.
- * The ESBAR process becomes fluxional upon electronic excitation.
Conclusions:
- * Akamptisomerism is potentially facilitated in the excited state via ESBAR.
- * ESBAR represents a promising photoswitching mechanism for porphyrinoid systems.
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