open access

https://hdl.handle.net/2115/83376

Flexible C-C Bonds: Reversible Expansion, Contraction, Formation, and Scission of Extremely Elongated Single Bonds

英語

thermal cycloreversion

2020-12-01

Wiley-Blackwell

Angewandte chemie-international edition

59(49)

22252-22257

Since carbon-carbon (C-C) covalent bonds are rigid and robust, the bond length is, in general, nearly constant and depends only on the bond order and hybrid orbitals. We report herein direct visualization of the reversible expansion and contraction of a C(sp(3))-C(sp(3)) single bond by light and heat. This flexibility of a C-C bond was demonstrated by X-ray analysis and Raman spectroscopy of hexaphenylethane (HPE)-type hydrocarbons with two spiro-dibenzocycloheptatriene units, the intramolecular [2+2] photocyclization of which and thermal cleavage of the resulting cyclobutane ring both occur in a single-crystalline phase. The force constant of the contracted C-C bond is 1.6 times greater than that of the expanded bond. Since formation of the cyclobutane ring and contraction of the C-C bond lower the HOMO level by approximately 1 eV, the oxidative properties of these HPEs with a flexible C-C bond can be deactivated/activated by light/heat.

学術雑誌論文

Accepted Manuscript

This is the peer reviewed version of the following article: Angewandte Chemie (International ed.) 59(49) December 1, 2020 pp.22252-22257 , which has been published in final form at https://doi.org/10.1002/anie.202010615. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.

1433-7851