Observation of a Thermally Accessible Triplet State Resulting from Rotation around a Main-Group π Bond

Arseni Kostenko; Boris Tumanskii; Miriam Karni; Shigeyoshi Inoue; Masaaki Ichinohe; Akira Sekiguchi; Yitzhak Apeloig

doi:10.1002/anie.201506291

Observation of a Thermally Accessible Triplet State Resulting from Rotation around a Main-Group π Bond

Arseni Kostenko, Boris Tumanskii, Miriam Karni, Shigeyoshi Inoue, Masaaki Ichinohe, Akira Sekiguchi, Yitzhak Apeloig

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30 Scopus citations

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.

Original language	English
Pages (from-to)	12144-12148
Number of pages	5
Journal	Angewandte Chemie International Edition in English
Volume	54
Issue number	41
DOIs	https://doi.org/10.1002/anie.201506291
State	Published - 1 Oct 2015
Externally published	Yes

Keywords

EPR spectroscopy
density functional calculations
diradicals
disilenes
zero-field splitting parameters

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10.1002/anie.201506291

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title = "Observation of a Thermally Accessible Triplet State Resulting from Rotation around a Main-Group π Bond",

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.",

keywords = "EPR spectroscopy, density functional calculations, diradicals, disilenes, zero-field splitting parameters",

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doi = "10.1002/anie.201506291",

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AU - Kostenko, Arseni

AU - Tumanskii, Boris

AU - Karni, Miriam

AU - Inoue, Shigeyoshi

AU - Ichinohe, Masaaki

AU - Sekiguchi, Akira

AU - Apeloig, Yitzhak

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N2 - 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.

AB - 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.

KW - EPR spectroscopy

KW - density functional calculations

KW - diradicals

KW - disilenes

KW - zero-field splitting parameters

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JF - Angewandte Chemie International Edition in English

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ER -

Observation of a Thermally Accessible Triplet State Resulting from Rotation around a Main-Group π Bond

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Keywords

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