Cross Conjugated Polyenes Derived from 2-Vinyl-butadiene: Electronic States of their Radical Cations, and Triplet Energy

✍ Scribed by Thomas Bally; Louis Neuhaus; Stephan Nitsche; Edwin Haselbach; Johann Janssen; Wolfgang Lüttke

• Publisher: John Wiley and Sons
• Year: 1983
• Tongue: German
• Weight: 380 KB
• Volume: 66
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19830660428

✦ Synopsis

Abstract

The doublet states of the radical cations of the cross conjugated polyenes 4,4‐dimethyl‐1‐methylidene‐2,5‐cyclohexadiene 2 and its bis‐derivative 1 have been investigated by photoelectron spectroscopy and by electronic spectroscopy of \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {1}^{+\kern-4pt {.} } $\end{document}^+^, prepared at 77 K in an electron scavenging matrix by γ‐irradiation. Simultaneous consideration of the spectral results shows \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {1}^{+\kern-4pt {.} } $\end{document} to be the second hydrocarbon molecular cation (after 2,2‐dimethyl isoindene) which possesses a first excited doublet state (D~1~) of non‐Koopmans nature (^2^B~3g~). The first Koopmans‐type excited state (^2^B~2g~) expected from PE. spectroscopy lies, however, very close in energy. In addition T~1~ of 1 was observed by electron energy loss spectroscopy at 2.0±0.1 eV. Application of the ‘SDT‐equation’ predicts for this state only 1.05 eV; there is at present no reasonable explanation for this failure.