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A thermally populated, perpendicularly twisted alkene triplet diradical

Variable-temperature NMR and ESR spectroscopic studies reveal that bis(dibenzo[a,i]fluorenylidene) possesses a singlet ground state, 1(S0), while the 90° twisted triplet(T1) is populated to a small extent already at room temperature. Analysis of the increasing amount of paramagnetic(T1) at temperatu...

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Bibliographic Details
Main Authors: Wentrup, Curt (Author) , Müller, Dennis (Author) , Comba, Peter (Author)
Format: Article (Journal)
Language:English
Published: 20 October 2016
In: Angewandte Chemie. International edition
Year: 2016, Volume: 55, Issue: 47, Pages: 14600-14605
ISSN:1521-3773
DOI:10.1002/anie.201607415
Online Access:Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1002/anie.201607415
Verlag, lizenzpflichtig, Volltext: https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.201607415
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Author Notes:Curt Wentrup, Michèle J. Regimbald‐Krnel, Dennis Müller, and Peter Comba
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Summary:Variable-temperature NMR and ESR spectroscopic studies reveal that bis(dibenzo[a,i]fluorenylidene) possesses a singlet ground state, 1(S0), while the 90° twisted triplet(T1) is populated to a small extent already at room temperature. Analysis of the increasing amount of paramagnetic(T1) at temperatures between 300 and 500 K yields the exchange interaction Jex/h c=3351 cm−1 and a singlet-triplet energy splitting of 9.6 kcal mol−1, which is in excellent agreement with calculations (9.3 kcal mol−1 at the UKS BP86/B3LYP/revPBE level of theory). In contrast, the zero-field splitting parameter D is very small (calculated value −0.018 cm−1) and unmeasurable.
Physical Description:Online Resource
ISSN:1521-3773
DOI:10.1002/anie.201607415

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