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Issue 16, 2019
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Theoretical study on the regioselective photoisomerization of asymmetric N,C-chelate organoboron compounds

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Abstract

Herein, the complete active space self-consistent field (CASSCF) and its second-order perturbation (CASPT2) methods combined with time-dependent density functional theory (TD-DFT) calculations were employed to investigate the isomerization reaction mechanisms of an asymmetric N,C-chelate organoboron compound, B(ppy)MesPh, in the ground (S0) state and the first singlet excited (S1) state. Our calculations show that isomerizations proceed via different pathways in the S0 and S1 states,; however, the energy barriers for mesityl isomerization are higher than those for phenyl isomerization in both states; this is in good agreement with the experimentally observed regioselectivity (S. Wang, et al. Angew. Chem., Int. Ed., 2017, 56, 6093–6097). Photoisomerization is motivated by charge transfer from two phenyl rings to the pyridyl moiety and initiated by the cleavage of the B–Cppy bond, followed by the formation of a boracyclopropane ring via an (S1/S0)X conical intersection and a biradical intermediate. Both steric and electronic features were found to be important for regioselective photoisomerization. Our results not only shed light on the experimental observations, but also provide valuable details on the excited state dynamics of organoboron compounds and can facilitate further syntheses and applications.

Graphical abstract: Theoretical study on the regioselective photoisomerization of asymmetric N,C-chelate organoboron compounds

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Publication details

The article was received on 29 Jan 2019, accepted on 20 Mar 2019 and first published on 20 Mar 2019


Article type: Paper
DOI: 10.1039/C9CP00569B
Citation: Phys. Chem. Chem. Phys., 2019,21, 8376-8383

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    Theoretical study on the regioselective photoisomerization of asymmetric N,C-chelate organoboron compounds

    F. Li, H. Zhu, Q. Li and Z. Li, Phys. Chem. Chem. Phys., 2019, 21, 8376
    DOI: 10.1039/C9CP00569B

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