Observation of a Thermally Accessible Triplet State Resulting from Rotation around a Main‐Group π Bond |
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| Authors: | Arseni Kostenko Dr Boris Tumanskii Dr Miriam Karni Prof Shigeyoshi Inoue Prof Masaaki Ichinohe Prof Akira Sekiguchi Prof Yitzhak Apeloig |
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| Institution: | 1. Schulich Faculty of Chemistry and Lise Meitner‐Minerva Center for Computational Quantum Chemistry, Technion‐Israel Institute of Technology, Haifa 32000 (Israel);2. Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305‐8571 (Japan) |
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| Abstract: | We report the first direct spectroscopic observation by electron paramagnetic resonance (EPR) spectroscopy of a triplet diradical that is formed in a thermally induced rotation around a main‐group π bond, that is, the Si?Si double bond of tetrakis(di‐tert‐butylmethylsilyl)disilene ( 1 ). The highly twisted ground‐state geometry of singlet 1 allows access to the perpendicular triplet diradical 2 at moderate temperatures of 350–410 K. DFT‐calculated zero‐field splitting (ZFS) parameters of 2 accurately reproduce the experimentally observed half‐field transition. Experiment and theory suggest a thermal equilibrium between 1 and 2 with a very low singlet–triplet energy gap of only 7.3 kcal mol?1. |
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| Keywords: | density functional calculations diradicals disilenes EPR spectroscopy zero‐field splitting parameters |
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